Identification of Late Pleistocene and Holocene fossil lizards from Hall’s Cave and a primer on morphological variation in North American lizard skulls

David T. Ledesma; Simon G. Scarpetta; John J. Jacisin; Antonio Meza; Melissa E. Kemp

doi:10.1101/2023.07.25.549934

Abstract

Fossil identification practices have a profound effect on our interpretation of the past because these identifications form the basis for downstream analyses. Therefore, well-supported fossil identifications are paramount for examining the impact of past environmental changes on populations and communities. Here we apply an apomorphic identification framework in a case study identifying fossil lizard remains from Hall’s Cave, a late Quaternary fossil site located in Central Texas, USA. We present images and descriptions of a broad comparative sample of North American lizard cranial elements and compile new and previously reported apomorphic characters for identifying fossil lizards. Our fossil identifications from Hall’s Cave resulted in a minimum of 11 lizard taxa, including five lizard taxa previously unknown from the site. Most of the identified fossil lizard taxa inhabit the area around Hall’s Cave today, but we reinforce the presence of an extirpated species complex of horned lizard. A main goal of this work is to establish a procedure for making well-supported fossil lizard identifications across North America. The data from this study will assist researchers endeavoring to identify fossil lizards, increasing the potential for novel discoveries related to North American lizards and facilitating more holistic views of ancient faunal assemblages.

Introduction

Fossils are valuable for providing a glimpse into past life on earth, and fossil data have played critical roles in understanding range shifts (Vasilyan and Bukhsianidze 2020), extinctions (Bochaton et al. 2019), and diversification during critical junctures in earth history (Smith et al. 2022). Paleontological data also lend a long-term perspective on the responses of taxa and ancient communities to environmental changes and have become increasingly important in conservation (Dietl et al. 2015). One of the first and most critical steps for incorporating fossils into ecological and evolutionary analyses is establishing fossil identifications. It is important to recognize that fossil identification practices have a profound effect on our interpretation of the past since these identifications form the basis for downstream analyses. Well-supported fossil identifications are paramount for examining past populations and communities and have been used to infer the impact of past environmental changes on North American Quaternary herpetofauna (non-avian reptiles and amphibians).

North American fossil herpetofaunas from the Quaternary period (2.56 Ma -present) were the subjects of numerous paleontological investigations during the 20^th century (see Holman 1995 and references therein). The cumulative findings of these investigators led to the formation of a hypothesis predicting relative taxonomic and biogeographic stability in North American herpetofauna throughout the Quaternary (Auffenberg and Milstead 1965), specifically during the last 1.8 million years (Holman 1995). This hypothesis was born out of the fact that paleoherpetologists who published on Quaternary fossils reported few extinct taxa, noted few to no speciation events, and found that identified species from fossil sites were generally congruent with species found in the area today (Brewer 1985). It was later argued, however, that this stability hypothesis was predicated on biased fossil identification practices that resulted in a circular argument for stability (Bell et al. 2010). Those biases include the historical practice of identifying Quaternary fossil herpetofauna using comparative extant specimens sourced from the immediate vicinity of the fossil deposit or within nearby circumscribed geopolitical or geographical regions. Using these geographically limited comparative datasets, fossils were commonly identified to the species level, sometimes based on ostensible vagueries (Bell et al. 2010). These practices effectively predetermined the taxonomic and geographic stability of Quaternary herpetofauna fossil assemblages (Bell et al. 2010). To address the circularity of the stability hypothesis, Bell et al. (2010) advocated for the use of apomorphies–evolutionary derived features–for making fossil identifications. Importantly, apomorphic identifications, when paired with an expansive comparative dataset, are less sensitive to geographic biases and provide a more objective and replicable system for identifying fossils.

Here we employ an apomorphy based identification framework to identify fossil lizard remains from a late Quaternary fossil site in Central Texas. Our study site, Hall’s Cave, is an exceptional study system because there is an abundance of well-preserved fossil material, including a sizable accumulation of fossil herpetofauna that would benefit from rigorous examination (Toomey 1993). Hall’s Cave contains the most complete late Quaternary stratigraphic sequence in Texas, spanning the last 20,000 years (Toomey 1993; Cook et al. 2003), and is located near the southern edge of the Edwards Plateau, an uplifted region occupying much of central Texas. Hall’s Cave was first excavated beginning in the late 1960s (then under the name Klein Cave; Roth 1972) and excavations continued in the late 80’s-early 90’s (Toomey 1993) as well as in recent years (Seersholm et al. 2020; Waters et al. 2021). Identification of fossil remains from these excavations largely focused on mammalian taxa (Toomey 1993; Smith et al. 2016) and plant microfossils (Cordova and Johnson 2019), but some herpetofauna were identified (Parmley 1988; Toomey 1993). Previous research on Hall’s Cave has also included bulk bone ancient DNA metabarcoding analyses, yet lizard ancient DNA was not recovered and amplified (Seersholm et al. 2020). Previous investigations of the fossil lizards from Hall’s Cave reported at least six different lizard taxa (Parmley 1988; Toomey 1993). Most of these identifications lacked a corresponding discussion of apomorphic morphological features supporting their taxonomic assignment. Here we reassess previously examined as well as new fossil lizard material from Hall’s Cave using an apomorphic identification framework.

In addition to identifying fossil lizards from Hall’s Cave, we also sought to establish a procedure for making well-supported fossil lizard identifications, particularly for North American lizards. We therefore compiled previously reported apomorphic characters as well as new potential apomorphies that can be used to identify fossil lizard remains from the Quaternary of North America. Furthermore, the Neogene and Quaternary fossil record for lizards is largely composed of tooth bearing elements from the upper and lower jaws (Holman 1995; Bell et al. 2010), yet it has been shown that there remain previously undiscovered apomorphies on other skeletal elements that are useful for fossil identification (Smith 2011). The authors of Bell et al. (2010) posited that the abundance of fossil lizard tooth bearing elements from the upper and lower jaws is due to a historical emphasis placed on mammal fossil collections and a general unfamiliarity of the larger lizard skeletal system. Therefore, for fossil skeletal elements examined here (Fig. 1), we also include images from a diverse set of North American lizard taxa to showcase morphological diversity and facilitate the recognition and identification of fossil lizard remains by paleontologists who do not specialize in lizard osteology.

Figure 1.

Skull of Diploglossus bilobatus TNHC 31933. A. Dorsal view; B. Lateral view; C. Ventral view; D. Mandible lateral view; E. Mandible medial view. Abbreviations: Co, Coronoid; Cp, Compound bone; D, Dentary; Ec, Ectopterygoid; F, Frontal; J, Jugal; Mx, Maxilla; N, Nasal; P, Parietal; Pof, Postorbitofrontal; Prf, Prefrontal; Pt, Pterygoid; Px, Premaxilla; Spl, Splenial; Sq, Squamosal; Q, Quadrate.

Methods

Fossils in this study were previously excavated from Hall’s Cave and are accessioned at the University of Texas Vertebrate Paleontology Collections (TxVP), locality 41229. We largely restricted our osteological comparative material to North American (NA) lizard taxa (see table 1 in Scarpetta et al. 2020) including those that today live on or north of the Isthmus of Panama, as well as those that inhabit Caribbean islands. Our comparative dataset was chiefly based on dry skeletal specimens; however, we also examined skeletons from specimens scanned using high-resolution computed tomography (CT). We aimed to get at least one specimen for every North American lizard family for our comparative dataset and for some families (e.g., Phrynosomatidae) we were able to sample all or nearly all genera. However, it was difficult to obtain comparative material for a few NA lizard families (e.g., Gymnophthalmidae) and so we instead relied on morphological evidence from the published literature. The full list of comparative specimens can be found in Table S1. Our phylogenetic framework follows that of Burbrink et al. (2020) for higher squamate relationships.

View this table:

Table 1. Identified fossil lizard taxa represented in Hall’s Cave from this study compared to previous studies.

We employed an apomorphy-based fossil identification framework using previously published apomorphies, as well as apomorphies we report here. Because our comparative dataset is largely restricted to NA lizard taxa, our fossil identifications are also geographically restricted on the continental scale. We were not able to examine every NA lizard species or clade and therefore take a conservative approach for fossil identifications. Apomorphies taken from the literature are listed in Table S2. Newly reported apomorphies can be found in the text and are based on our NA restricted comparative dataset. We note that newly reported apomorphies must be examined in non-NA taxa before being used in a global scale apomorphic diagnosis. Anatomical terminology follows that of Evans (2008) unless otherwise noted and many of the anatomical structures referenced in the text are labeled in Figure 2. We were able to base our fossil descriptions on one or a few exemplar fossil specimens because we observed no substantive differences between exemplar and other referred specimens, unless otherwise noted.

Figure 2.

Cranial elements of Diploglossus bilobatus TNHC 31933 with relevant anatomical structures labeled”. A. Premaxilla in anterior view; B-C. Right maxilla in medial and dorsal views; D. Left nasal dorsal view; E-F. Right frontal dorsal and lateral views; G. Parietal in dorsal view; H. Right prefrontal lateral view; I. Right jugal lateral view; J. Right postorbitofrontal dorsal view; K. Right squamosal lateral view; L. Left quadrate posterior view; M. Right pterygoid dorsal view; N-O. Right ectopterygoid ventral and lateral views; P. Right dentary medial view; Q. Left coronoid lateral view; R. Right splenial medial view; S. Left compound bone dorsal view. Scale bar = 1 mm. Abbreviations: add.fo, adductor fossa; al.pr, anterolateral process; alv.p, alveolar plate; a.m.f, anterior mylohyoid foramen; am.pr, anteromedial process; An.pr, Angular process; a.pr, anterior process; art.s, articular surface; cch, conch; c.co, central column; ce.co, cephalic condyle; Co.pr, Coronoid process; cr.cr, cristae cranii; cr.tr, crista transversalis; d.o, dorsal ossification; fa.pr, facial process; f.co, fossa columella; ims, intramandibular septum; ip.s, interparietal shield; l.pr, lateral process; ma.co, mandibular condyle; m.cr, medial crest; Mk.g, Meckelian groove; Mx.ft, maxilla facet; Mx.lp, maxillary lappet; n.pr, nasal process; o.pr, orbital process; pa.pl, palatal plate; Pa.pr, palatine process; pl.pr, posterolateral process; pm.pr, posteromedial process; pp.pr, postparietal process; p.pr, posterior process; Pt.ft, Pterygoid facet; pv.pr, posteroventral process; Px.pr, premaxillary process; qj.pr, quadratojugal process; Q.pr, Quadrate process; rapr, retroarticular process; s.a.f, superior alveolar foramen; Sa.pr, surangular process; sm.l, suprameckelian lip; sn.pr, supranarial process; so.pr, suborbital process; Spl.s, Splenial spine; t.pr, transverse process; ty.cr, tympanic crest; v.pr, ventral process.

Systematic Paleontology

Iguania Cuvier, 1817

Pleurodonta Cope, 1864

Referred specimens: See Table S3.

Nasal

Description

TxVP 41229-25562 is a right nasal (Fig. 3). There is a long anteromedial process with a lateral articulation facet for the premaxilla. There is a shorter anterolateral process. The posterior end is narrow compared to the anterior end. The ventral surface is concave, and there are two foramina that pierce the bone vertically.

Figure 3.

Fossil pleurodontans. TxVP 41229-29095 Anterior view of premaxilla; TxVP 41229-27039 Dorsal and medial view of right maxilla; TxVP 41229-25562 Dorsal view of nasal; TxVP 41229-28800 Dorsal view of frontal; TxVP 41229-28505 Dorsal view of parietal; TxVP 41229-25836 Dorsal view of parietal; TxVP 41229-25945 Lateral and medial view of left jugal; TxVP 41229-28355 Lateral view of left squamosal; TxVP 41229-27010 Dorsolateral view of left postorbital; TxVP 41229-26975 Dorsolateral view of left postorbital; TxVP 41229-28984 Dorsolateral view of left postorbital; TxVP 41229-25579 Posterior view of left quadrate. Scale bars = 1 mm.

Identification

The fossil shares with pleurodontans a supranarial process (Gauthier et al. 2012), although the process is much longer in some pleurodontan taxa (e.g., Dipsosaurus dorsalis), and a nasal that gradually narrows posteriorly. A supranarial process is also present in some non-iguanians but it is usually small except for Diploglossus bilobatus (Fig. 4). The fossil nasal distinctly narrows posteriorly similar to that observed in many examined North American lizards pleurodontans (Fig. 5). The fossil nasal differs from non-pleurodontan North American lizards, except for Anelytropsis papillosus, in rapidly tapering posteriorly, resulting in a posterior end that is much narrower compared to the anterior end. Anelytropsis papillosus differs from the fossil in lacking a supranarial process. Furthermore, many non-pleurodontan North American lizards, and anguimorphs in particular, differ from the fossil in often having a distinct rugose dorsal surface of the nasal.

Figure 4.

Non-Pleurodontan Nasals. Nasals in dorsal view– A. Anelytropsis papillosus UF 86708; B. Coleonyx variegatus TxVP M-12109; C. Plestiodon gilberti TxVP M-8587; D. Xantusia riversiana TxVP M-8505; E. Xantusia virigatus TxVP M-12130; F. Lepidophyma lowei LACM 143367; G. Aploglossus plicatus TNHC 34481; H. Aspidoscelis sonorae TxVP M-15670; I. Bipes canaliculatus CAS 134753; J. Heloderma suspectum TxVP M-9001; K. Xenosaurus grandis TxVP M-8960; L. Diploglossus bilobatus TNHC 31933; M. Anniella pulchra TxVP M-8678; N. Ophisaurus attenuatus TxVP M-8979; O. Gerrhonotus infernalis TxVP M-13441; P. Elgaria velazquezi SDNHM 68677. Scale bars = 1 mm.

Identification

TxVP 41229-28355 shares with Pleurodonta, some teiids, and xenosaurids a posterodorsal process (Estes et al. 1988; Fig. 12). Some examined Aspidoscelis (e.g., A. tigris TxVP M-13877) and other teiids (e.g., Ameiva sp. TxVP M-8459) also have a distinct dorsal and ventral projection on the posterior end of the squamosal (Tedesco et al., 1999; Evans 2008). However, the posteroventral process projects ventrally or posteriorly in examined Ameiva (Evans 2008) and Aspidoscelis, and the posteroventral process is often shorter and less distinct in examined Aspidoscelis (Fig. 13). The dorsal process of Xenosaurus differs in that it is developed into a broad sheet and more anteriorly located along the squamosal (Bhullar 2011). On this basis, the fossil was assigned to Pleurodonta. The fossil and crotaphytids differ from iguanids, Enyalioides heterolepis, and phrynosomatids in having a longer and more distinct posterodorsal process of the squamosal (de Queiroz 1987). In some crotaphytids (e.g., C. bicinctores TxVP M-8612, M-8947) the posterodorsal process is less distinct than in other Crotaphytus because it is connected with the main rod by a broad sheet of bone, but no fossils were found with this morphology. Most corytophanids, except Laemanctus longipes, have a relatively shorter posterodorsal process (Smith 2011), and Laemanctus longipes differs in having a distinctly downturned main rod of the squamosal. Anolis and Leiocephalus also have a shorter posterodorsal process compared to the fossil and crotaphytids (Pregill 1992; Smith 2011). The posterodorsal process is long among Polychrus (Smith 2011); however, Polychrus differs in having a relatively shorter main rod of the squamosal and may have lateral protuberances (Smith 2011). On this basis, the fossil was assigned to Crotaphytidae.

Figure 12.

Pleurodontan Squamosals. Squamosals in lateral and posterior views– A. Sceloporus clarkii TxVP M-12157; B. Uma exsul TNHC 30247; C. Phrynosoma cornutum TxVP M-6405; D. Phrynosoma douglasii TxVP M-8526; E. Phrynosoma modestum TNHC 95921; F. Iguana iguana TxVP M-8454; G. Ctenosaura hemilopha TxVP M-8616; H. Dipsosaurus dorsalis TxVP M-9285; I. Sauromalis ater TxVP M-11599; J. Anolis carolinensis TxVP M-9042; K. Crotaphytus collaris TxVP M-12468; L. Gambelia sila TNHC 95261; M. Basiliscus basiliscus TxVP M-11907; N. Corytophanes sp. TxVP M-16765; O. Leiocephalus carinatus TNHC 89274; P. Leiocephalus psammodromus TNHC 103220; Q. Polychrus gutturosus TNHC 24152; R. Enyalioides heterolepis UF 68015. Scale bars = 1 mm.

Figure 13.

Non-Pleurodontan Squamosals. Squamosals in lateral view– A. Anelytropsis papillosus UF 86708; B. Coleonyx elegans UF 11258; C. Plestiodon gilberti TxVP M-8587; D. Xantusia riversiana TxVP M-8505; E. Xantusia virigatus TxVP M-12130; F. Lepidophyma lowei LACM 143367; G. Aploglossus plicatus TNHC 34481; H. Aspidoscelis sonorae TxVP M-15670; I. Bipes canaliculatus CAS 134753; J. Heloderma suspectum TNHC 62766; K. Xenosaurus grandis TxVP M-8960; L. Diploglossus bilobatus TNHC 31933; M. Ophisaurus attenuatus TxVP M-8979; N. Gerrhonotus infernalis TxVP M-13441; O. Barisia imbricata TNHC 76984. Scale bars = 1 mm.

Quadrate

Description

TxVP 41229-25579 is a left quadrate that is well preserved but is missing the dorsolateral portion of the bone (Fig. 3). The central column is wide, and the bone narrows ventrally. There is no pterygoid lappet, but there is a well-developed and anteromedially directed medial crest. The conch is deep, gradually slants laterally from the central column, and narrows ventrally. The cephalic condyle projects posteriorly and there is no extensive ossification dorsally. The dorsal margin is straight past the lateral extent of the mandibular condyle. There is a foramen medial to the central column.

Identification

TxVP 41229-25579 shares with geckos, Scincella, Xantusia, some pleurodontans, and anguimorphs (besides Heloderma) the absence of a distinct pterygoid lappet (Estes et al. 1988; Evans 2008). The fossil quadrate differs from that of geckos and Xantusia in being relatively wide overall and with a wide central column (Kluge 1962; Evans 2008). The fossil and pleurodontans differ from anguimorphs in having a quadrate that widens dorsally. On this basis, the fossil was identified to Pleurodonta. Compared to the fossil and examined crotaphytids, the quadrate of Dipsosaurus dorsalis is much wider dorsally relative to the articular surface, the conch is deeper, and the pterygoid lamina does not extend as far anteriorly (Fig. 14). The quadrate of a small Iguana iguana (TxVP M-13054; SVL = 90 mm) is much slenderer and has a reduced pterygoid lamina compared to the fossil and crotaphytids. Larger Iguana iguana differ from the fossil and crotaphytids in that the pterygoid lamina is extended medially such that the central column is vertically oriented and near the midline of the bone (Iguana iguana OUVC 10612). The quadrate of most examined Sauromalus (except Sauromalis ater TNHC 18483) differ in having a low dorsolateral portion, such that the dorsal margin of the bone is sloped ventrolaterally. Additionally, the quadrate of Sauromalus has a dorsomedial expansion that contacts the paroccipital process (Evans 2008) and which is especially prominent in large specimens. Ctenosaura differs in having a more distinct and curved tympanic crest and a deeper conch. In Anolis there is a distinct boss at the ventromedial margin of the bone below the articulation with the pterygoid. In Anolis and Polychrus, the lateral and medial margins are more parallel compared to the fossil and crotaphytids. Leiocephalus barahonensis (USNM 260564) and L. carinatus differ from crotaphytids in having a medially expanded pterygoid lamina that extends medially beyond the dorsomedial corner of the quadrate (see also fig. 6 in Bochaton et al. 2021). Leiocephalus psammodromus differs from crotaphytids in having a quadrate that is not as distinctly widened dorsally and having a distinct medial notch where the pterygoid articulates. The quadrate conch of Enyalioides heterolepis is more shallow compared to the fossil and crotaphytids. The quadrate of Basiliscus basiliscus is proportionally taller and the central column more slender. The quadrate is exceptionally slender in examined Corytophanes and Laemanctus (Lang 1989). The quadrate of phrynosomatids, except for Phrynosoma, differs from crotaphytids in having a more curved lateral margin (tympanic crest) (Mead 1988). Additionally, the central column is more slender near the base and the conch is deeper in examined large-bodied Sceloporus (e.g., S. clarkii, Fig. 14). The quadrate of Phrynosoma differs from the fossil and crotaphytids in having a reduced pterygoid lamina, a dorsal portion of the bone that is much wider than the ventral portion, and a conch that remains deep lateral to the central column. Based on these differences, quadrates were assigned to Crotaphytidae.

Figure 14.

Pleurodontan Quadrates. Quadrates in posterior view– A. Sceloporus clarkii TxVP M-12157; B. Holbrookia maculata TxVP M-14322; C. Cophosaurus texanum TxVP M-8527; D. Uma scoparia TxVP M-8529; E. Uma exsul TNHC 30247; F. Phrynosoma cornutum TxVP M-6405; G. Phrynosoma douglasii TxVP M-8526; H. Phrynosoma modestum TNHC 95921; I. Petrosaurus thalassinus TxVP M-9612; J. Iguana iguana TxVP M-8454; K. Ctenosura hemilopha TxVP M-8616; L. Dipsosaurus dorsalis TxVP M-13086; M. Sauromalis ater TxVP M-11599; N. Anolis carolinensis TxVP M-9042; O. Crotaphytus collaris TxVP M-12468; P. Gambelia sila TNHC 95261; Q. Basiliscus basiliscus TxVP M-11907; R. Corytophanes sp. TxVP M-16765 S. Leiocephalus carinatus TNHC 89274; T. Leiocephalus psammodromus TNHC 103220; U. Polychrus gutturosus TNHC 24152; V. Enyalioides heterolepis UF 68015. Scale bars = 1 mm.

Pterygoid

Description

TxVP 41229-28513 is a pterygoid that is missing only the distal end of the palatine process (Fig. 15). The palatine process is thin near its base and the transverse process extends laterally at nearly a 90-degree angle with the quadrate process. The transverse process is dorsoventrally tall, and the distal end is oriented near vertical. There is a distinct ridge on the dorsal surface for insertion of the superficial pseudotemporal muscle and a distinct ectopterygoid facet just anterior to that. There is a large ridge on the ventral surface for insertion of the pterygomandibular muscle and a small, deep fossa columella that continues posteriorly as a short, narrow groove. The quadrate process is elongated, and the medial surface has an elongate groove that serves for insertion of the pterygoideus muscle. There is a ventromedial projection at the floor of the basipterygoid fossa. There is a long patch of 17 tooth positions filled with 16 pterygoid teeth. There are four small foramina on the dorsal surface in the area from the palatine process to just anterior to the fossa columella. There are two foramina just anterior to the ridge for insertion of the pterygomandibular muscle. TxVP 41229-27144 and TxVP 41229-28866 are missing portions of the palatine and quadrate processes, and do not differ substantively from TxVP 41229-28513.

Figure 15.

Fossil crotaphytids. TxVP 41229-27144 Dorsal and ventral view of right pterygoid; TxVP 41229-28513 Dorsal and ventral view of left pterygoid; TxVP 41229-25592 Posterior and ventral view of right ectopterygoid; TxVP 41229-27575 Medial view of left dentary; TxVP 41229-25853 Dorsal view of left compound bone; TxVP 41229-25613 Dorsal view of left articular; TxVP 41229-25578 Lateral and medial view of right coronoid. Scale bars = 1 mm.

Identification

Pterygoids are assigned to Pleurodonta based on the presence of a well-developed ventromedial projection at the floor of the basipterygoid fossa (Evans 2008; Smith 2009b; Fig. 16). A ventromedial projection at the floor of the basipterygoid fossa is also in some non-pleurodontans (e.g., Ophisaurus), but it is less distinct than in the fossil and in many pleurodontans (e.g., Crotaphytus). Among pleurodontans, pterygoid teeth are absent in phrynosomatids and are variably present in Anolis, Polychrus, Dipsosaurus, and Leiocephalus (Etheridge and de Queiroz 1988). The palatal plate in Anolis and phrynosomatids is broad relative to the fossils. Compared with the fossils, Sauromalus has a shorter transverse process and a shorter quadrate process. The quadrate process in Iguana iguana is more distinctly short and the fossa columella elongated. Pterygoid teeth of examined Ctenosaura are oriented more oblique (Mahler and Kearney 2006), and the palatal plate is stepped along the anterior edge (Oelrich 1956). An examined Ctenosaura clarki (TxVP M-14824) has a unique ridge on the ventral surface of the pterygoid along which the teeth are positioned. Dipsosaurus dorsalis has a narrow linear notch on the transverse process not seen on the fossils. The transverse process is shorter and less robust in Enyalioides heterolepis. Basiliscus and Corytophanes have a taller quadrate process and tend to have longer pterygoid teeth which may be slightly recurved in Basiliscus (Lang 1989). Basiliscus and Laemanctus generally have fewer pterygoid teeth ranging from three to five in number (Lang 1989). The shelf under the basipterygoid fossa is less extensive in Basiliscus basiliscus. The quadrate process is anteroposterioly shorter, and the transverse process is exceptionally tall in Corytophanes. Among North American pleurodontans, the largest number of pterygoid teeth is found in crotaphytids and Ctenosaura which can have a similar number of tooth positions to the fossils (Taylor 1940). However, there is a large amount of variation in the number of pterygoid teeth among crotaphytids (Taylor 1940). The transverse process of the fossils and of Crotaphytus is more dorsoventrally elongated and less pointed in dorsal view compared to examined Leiocephalus. Pterygoids are assigned to Crotaphytidae based on the differences from other NA pleurodontans described above.

Figure 16.

Pleurodontan Pterygoids. Pterygoids in dorsal view– A. Sceloporus clarkii TxVP M-12157; B. Petrosaurus mearnsi TxVP M-14910; C. Uma exsul TNHC 30247; D. Phrynosoma cornutum TxVP M-6405; E. Phrynosoma douglasii TxVP M-8526; F. Iguana iguana TxVP M-8454; G. Ctenosaura hemilopha TxVP M-8616; H. Dipsosaurus dorsalis TxVP M-13086; I. Sauromalis ater TxVP M-11599; J. Anolis carolinensis TxVP M-9042; K. Crotaphytus collaris TxVP M-12468; L. Gambelia sila TNHC 95261; M. Basiliscus basiliscus TxVP M-11907; N. Corytophanes sp. TxVP M-16765; O. Leiocephalus carinatus TNHC 89274; P. Leiocephalus psammodromus TNHC 103220; Q. Polychrus gutturosus TNHC 24152; R. Enyalioides heterolepis UF 68015. Scale bars = 1 mm.

Ectopterygoid

Description

TxVP 41229-25592 is a right ectopterygoid (Fig. 15). It has distinct anterolateral and posterolateral processes. The ventral corner of the posterolateral process is narrow and extends far ventrally. There is a groove for articulation with the maxilla on the anterolateral edge of the bone below the dorsal corner. The dorsal surface is slightly concave at the lateral end and the pterygoid process extends far ventrally. The pterygoid facet is deep with a distinct overhanging corner of bone dorsally. The main shaft of the ectopterygoid is orthogonal to the lateral edge of the bone and there are two small foramina within the jugal facet.

Identification

TxVP 41229-25592 share with iguanians, xantusiids, and xenosaurids the presence of an elongate posterolateral process on the ectopterygoid (Smith 2009b). The ectopterygoid (=os transversum of Young 1942) of Xantusia can be distinguished from that of pleurodontans in being a broad triangular plate (Young 1942; Fig. 17). The ectopterygoid of xenosaurids differs from pleurodontans in having the main shaft of the bone oriented more anteroposteriorly in the skull and in having a much shorter posterolateral process (Bhullar 2011). Among NA pleurodontans, Anolis differs from the fossil and Crotaphytidae in lacking a flange on the lateral head that articulates ventrally or ventromedially with the maxilla, and in having a main shaft that is oblique relative to the lateral face of the bone (Smith 2009b; Fig. 18). The main shaft of the ectopterygoid is slightly oblique relative to the lateral face of the bone in some corytophanids, including Corytophanes hernandesii and Laemanctus longipes (Smith 2011). In phrynosomatids, Leiocephalus, and Enyalioides heterolepis, the main shaft of the ectopterygoid is also slightly oblique relative to the lateral face of the bone, while in the fossil and Crotaphytus, the main shaft is orthogonal to the lateral face of the bone. Additionally, the shaft of the bone is much more slender in non-Phrynosoma phrynosomatids compared to the fossil and Crotaphytus. The ventral corner of the posterolateral process of the ectopterygoid in the fossil and Crotaphytus is developed into a distinct wedge that projects ventrally, similar to that seen in corytophanids (Smith 2011). The ventral corner of the posterolateral process is well-developed in crotaphytids, corytophanids, and Dipsosaurus dorsalis, semi-developed in Ctenosaura hemilopha, and undeveloped in Sauromalus ater and Ctenosaura similis (Smith 2011). Although the ventral corner of the posterolateral process is well-developed in Dipsosaurus dorsalis, it does not project as far ventrally as in corytophanids and Crotaphytus collaris. In Crotaphytus collaris there is a corner of bone dorsal to the posterior pterygoid facet that is downturned. This downturned corner is also present in Laemanctus longipes, some Anolis, and Enyalioides laticeps, although it is absent in other hoplocercids (Smith 2011). A downturned corner is absent in Polychrus and Gambelia wislizenii (Smith 2011). The fossil ectopterygoid can be referred to Crotaphytidae based on possessing a main shaft that is nearly orthogonal to the lateral face of the bone, a wide shaft of the ectopterygoid, a ventral corner of the posterolateral process of the ectopterygoid developed into a distinct wedge that projects ventrally, and a downturned corner of bone dorsal to the posterior pterygoid facet. A downturned corner of bone dorsal to the posterior pterygoid facet is absent in Gambelia wislizenii (Smith 2011). A slightly downturned corner is present in Gambelia sila (TxVP M-95261), although not to the extent seen in Crotaphytus. More information on this feature among species of Gambelia is needed before a confident generic assignment can be made.

Identification

Compound bones are referred to Pleurodonta based on the presence of an angular process and a posteriorly directed retroarticular process that is not broadened posteriorly (Estes et al. 1988; Fig. 21). Teiids also have a posteriorly directed retroarticular process that is not broadened posteriorly; however, the adductor fossa in teiids is greatly expanded for insertion of the m. adductor mandibulae posterior into Meckel’s canal (Estes et al. 1988) and the angular process is deflected further ventrally compared to pleurodontans (Tedesco et al. 1999; Morales et al. 2019). Among NA pleurodontans, the retroarticular process is reduced in Polychrus and the angular process is more horizontally oriented in Dipsosaurus dorsalis (Smith 2011) compared to crotaphytids. The medial crest is more distinct in Dipsosaurus dorsalis, Iguana iguana, Ctenosaura similis, and Enyalioides compared to crotaphytids (Smith 2011). Sauromalus differs from the fossil and crotaphytids in having a short triangular angular process (Smith 2011). In Laemanctus and Corytophanes, the angular process is short, and the angular process in Basiliscus basiliscus does not project as far medially compared to Crotaphytus collaris (see fig. 71 in Smith 2011). Leiocephalus differs from the fossil and crotaphytids in having a wider and rounded retroarticular process (Bochaton et al. 2021). In phrynosomatids and in Anolis, the angular process is connected to the retroarticular process by a sheet of bone that is more extensive than seen in examined crotaphytid specimens; however, one large specimen of Sceloporus clarkii (TxVP M-12202) has a reduced connection between the angular and retroarticular process. That specimen lacks a medial crest and a relatively wide retroarticular process, distinguishing it from examined crotaphytids. Fossils are assigned to Crotaphytidae based on an elongate, thin retroarticular process, an elongate and ventrally slanted angular process, a short medial crest on the retroarticular process, and a reduced lamina of bone connecting the angular process and retroarticular process. Crotaphytus differs from Gambelia in having a distinct knob-like process just anterolateral to the articular surface (lateral process of McGuire 1996) and having a more reduced shelf of bone connecting the body of the surangular to the dorsal tubercle anterior to the articular surface (McGuire 1996). A distinct knob-like process just anterolateral to the articular surface was not observed on some examined specimens of Crotaphytus collaris, so this feature likely varies intra- or interspecifically within Crotaphytus. A shelf of bone anterior to the dorsal tubercle is absent in most specimens of Crotaphytus, and a small shelf is present in specimens of Gambelia wislizenii. A small shelf is also reported in other species of Crotaphytus (McGuire 1996) so the presence of a shelf alone cannot be used to diagnose a fossil to Gambelia; however, only Crotaphytus lack the shelf (McGuire 1996). A distinct ridge on the dorsolateral surface of the surangular reportedly occurs in Crotaphytus and is reduced or absent in Gambelia (McGuire 1996). We could not identify a distinct ridge on the dorsolateral surface of the surangular in examined specimens of Crotaphytus, so this feature likely varies intra- or interspecifically within Crotaphytus and may be related to the development of the m. adductor mandibularis externus (McGuire 1996).

Figure 21.

Pleurodontan Compound bones. Compound bones in dorsal view– A. Sceloporus clarkii TxVP M-12157; B. Sceloporus graciosus TxVP M-14879; C. Cophosaurus texanum TxVP M-8527; D. Holbrookia maculata TxVP M-14322; E. Uma exsul TNHC 30247; F. Phrynosoma cornutum TxVP M-6405; G. Phrynosoma douglasii TxVP M-8526; H. Phrynosoma modestum TNHC 95921; I. Iguana iguana TxVP M-8454; J. Ctenosaura hemilopha TxVP M-8616; K. Sauromalis ater TxVP M-11599; L. Dipsosaurus dorsalis TxVP M-13086; M. Anolis carolinensis TxVP M-9042; N. Crotaphytus collaris TxVP M-12468; O. Gambelia sila TNHC 95261; P. Leiocephalus psammodromus TNHC 103220; Q. Leiocephalus carinatus TNHC 89274; R. Corytophanes sp. TxVP M-16765; S. Basiliscus vittatus TxVP M-8554; T. Polychrus gutturosus TNHC 24152; U. Enyalioides heterolepis UF 68015. Scale bars = 1 mm.

Phrynosomatidae Fitzinger, 1843

Referred specimens: See Table S3.

Maxilla

Description

TxVP 41229-27461 and TxVP 41229-27044 serve as the basis for our description (Fig. 22). TxVP 41229-27461 is a right maxilla with 22 tooth positions. Teeth are tricuspid except for the mesial teeth, and teeth are slender throughout the tooth row with bases near equal in width compared to the crowns. The facial process is broken dorsally and is curved medially with a distinct canthal crest. The facial process diminishes and merges with the crista transversalis, which extends anteromedially. There is a depression dorsally on the premaxillary process. The palatine process is present but broken. Dorsally the postorbital process has a groove that widens posteriorly for articulation with the jugal. Laterally there is a longitudinal ridge on the postorbital process. There is a superior alveolar foramen medial to the palatine process. There are three foramina on the premaxillary process, one anterior to the facial process (anterior inferior alveolar foramen), one on the crista transversalis (anterior inferior alveolar foramen), and one anteromedially on the premaxillary process (subnarial arterial foramen). There are eight lateral nutrient foramina. TxVP 41229-27044 differs in having 17 tooth positions, a less defined dorsal depression on the premaxillary process, no longitudinal ridge on the postorbital process, a flat dorsal surface of the postorbital process, a distinct asymmetric palatine process, two superior alveolar foramina, and four lateral nutrient foramina.

Description

TxVP 41229-26976 is a right prefrontal (Fig. 22). It is triradiate with a long and pointed orbital process, a short ventral process, and an anterior main body developed into a sheet of bone. The anterior sheet is slightly broken and has a broad articulation facet for the facial process of the maxilla. There is a distinct ridge on the lateral surface near the base of the orbital process that is continuous with a large lateral boss. The ventral process is narrow and squared-off. There is a distinct notch for the lacrimal foramen, and the ventral process forms the posterior border of the foramen. Medially, the boundary of the olfactory chamber is a smooth, rounded, and concave surface. Dorsal to the olfactory chamber is a shallow groove for articulation with the frontal. The orbitonasal flange is narrow.

Identification

The fossil shares with pleurodontans and teiids the presence of a distinct prefrontal boss (Gauthier et al. 2012; Fig. 23). The fossil and prefrontals of many pleurodontans differ from teiids in having a boss that widens ventrally and is semicircular or tear-dropped shaped (Smith 2009a). Additionally, teiids differ in having a thin, laterally projecting lamina with a distinct articulation facet for the facial process of the maxilla (Tedesco et al. 1999). Basiliscus, Polychrus, and Anolis differ from the fossil in often having a more prominent boss or a strong lateral canthal ridge (Smith 2011). The prefrontal boss is larger in adult Cyclura and Iguana compared to the fossil (Smith 2011), and juvenile Iguana differ in having an exceptionally thin ventral process. Corytophanes and Laemanctus differ from the fossil in having rugosities on the dorsal surface (Smith 2011). Furthermore, Corytophanes differs from the fossil in having a long supraorbital process, and Laemanctus differs in having a posterior process that is directed more posteriorly (Smith 2011). Crotaphytus differs from the fossil in having the prefrontal boss slightly obscure the lacrimal notch in lateral view. Examined Gambelia differ in having a more distinct boss that projects farther laterally. The ridge dorsal to the prefrontal boss is wider in examined Leiocephalus compared to the fossil. Enyalioides heterolepis differs from the fossil in having a more bulbous prefrontal boss. The fossil differs from other NA pleurodontans and shares several features with phrynosomatids excluding Phrynosoma, which has a long supraorbital process, and phrynosomatines that have a prefrontal boss developed into a laterally projecting thin lamina (e.g., Cophosaurus and Holbrookia).heterolepis

Figure 23.

Pleurodontan Prefrontals. Prefrontals in lateral view– A. Sceloporus clarkii TxVP M-12157; B. Petrosaurus mearnsi TxVP M-14910; C. Cophosaurus texanum TxVP M-8527; D. Uma exsul TNHC 30247; E. Phrynosoma cornutum TxVP M-6405; F. Phrynosoma douglasii TxVP M-8526; G. Phrynosoma modestum TNHC 95921; H. Iguana iguana TxVP M-13054; I. Ctenosura hemilopha TxVP M-8616; J. Dipsosaurus dorsalis TxVP M-13086; K. Sauromalis ater TxVP M-11599; L. Anolis carolinensis TxVP M-9042; M. Crotaphytus collaris TxVP M-12468; N. Gambelia sila TNHC 95261; O. Basiliscus basiliscus TxVP M-11907; P. Corytophanes sp. TxVP M-16765; Q. Leiocephalus psammodromus TNHC 103220; R. Polychrus gutturosus TNHC 24152; S. Enyalioides heterolepis UF 68015. Scale bars = 1 mm.

Jugal

Description

TxVP 41229-27734 is a left jugal (Fig. 22). There is a maxillary facet laterally and ventrally on the suborbital process. The dorsal margin of the suborbital process is everted laterally and there is a groove on the medial surface. There is no quadratojugal process. There is a ridge on the anteromedial edge of the postorbital process and a postorbital facet anteriorly. The postorbital process is posteriorly directed and concave posteriorly. There is a foramen medially near the inflection point, two foramina anteriorly on the postorbital process, and many small foramina along the lateral surface. TxVP 41229-27968 differs in having an elongate depression dorsally on the suborbital process, a tall lateral edge of the suborbital process with an upturned corner at the anterior end, and a postorbital process that curves posteromedially.

Identification

Jugals were assigned to Pleurodonta based on the absence of a quadratojugal process (Gauthier et al. 1988; Smith 2009a). Xantusia also lack a quadratojugal process but differ from pleurodontans in having an exceptionally short and thin suborbital process (Young 1942). Among NA pleurodontans, the fossil shares with Phrynosomatidae and Crotaphytidae a posteriorly deflected distal end of the postorbital process (Smith 2009a); however, crotaphytids differ in having a quadratojugal process.

Postorbital

Description

Morphotype A: TxVP 41229-27522 is a right postorbital (Fig. 22). The fossil is triradiate with thin anterior process and dorsal processes and a wider posterior process. The anterior and dorsal processes are relatively straight. There is a small articulation facet anteromedially on the orbital process and there are distinct jugal and squamosal facets along the ventrolateral edge.

Morphotype B: TxVP 41229-25584 is a right postorbital (Fig. 22). The bone is triradiate with thin anterior, dorsal and posterior processes. The ventrolateral margin is concave below the anterior portion and the posterior process is slightly curved dorsally. The dorsal process is concave anteriorly without an anterior articulation facet. There are distinct jugal and squamosal facets that are visible in dorsolateral view.

Identification

Postorbitals were identified to Pleurodonta based on a sub-triangular morphology with a distinct ventral process (Estes et al. 1988). The fossils share with phrynosomatids, Anolis, some iguanids, and some Leiocephalus a smooth lateral face of the dorsal process (Smith 2009a, b; Smith 2011). The posterior process in Ctenosaura (see also fig. 40G of Smith 2011) is proportionally more elongated compared to the fossils. Dipsosaurus dorsalis differs in often having a flangelike expansion on the orbital process (Smith 2011). Iguana generally has a wider orbital process compared to the fossil and phrynosomatids excluding Phrynosoma. The postorbital of Sauromalus and Dipsosaurus dorsalis is more straight in anterior view compared to the fossils and phrynosomatids (Smith 2011). Anolis differs from the fossils and phrynosomatids in having an articulation facet visible on the lateral or anterolateral surface of the orbital process as it underlaps the frontoparietal corner (Smith 2009a). The postorbital of Leiocephalus differs from the fossils in lacking a distinct squamosal facet along the ventrolateral edge (see also fig. 3F of Bochaton et al. 2021). The postorbitals of examined Uta, Urosaurus, Cophosaurus, and Callisaurus have a slender build relative to Sceloporus and are more similar to Morphotype B. Sand lizards differ from sceloporines in lacking a postfrontal (Cox and Tanner 1977) and therefore also lack a postfrontal articulation surface on the postorbital. Fossils identified to morphotype A likely represent Sceloporus or Petrosaurus and fossils identified to morphotype B likely represent sand lizards.

Pterygoid

Description

TxVP 41229-27488 and TxVP 41229-27011 serve as the basis for our description (Fig. 24). TxVP 41229-27488 is a left pterygoid that is missing the distal end of the transverse process. The palatine process is broad at the base and has a palatine facet anteriorly. The transverse process extends laterally at nearly a 90-degree angle with the quadrate process. The transverse process is dorsoventrally tall and bears a distinct ectopterygoid facet. There is a distinct ridge on the dorsal surface for insertion of the superficial pseudotemporal muscle. There is a large ridge on the ventral surface for insertion of the pterygomandibular muscle and a deep fossa columella without a pterygoid groove. The quadrate process is elongated, and the medial surface has a groove that serves for insertion of the pterygoideus muscle. There is a medial groove dorsal to a shelf-like projection at the floor of the basipterygoid fossa. There are no pterygoid teeth, but there is a large hole on the ventral surface of the palatal plate along with several smaller foramina on both the dorsal and ventral surface. TxVP 41229-27011 is smaller than TxVP 41229-27488 and the distal end of the transverse process is pointed and tall vertically.

Description

TxVP 41229-26883 is a left splenial (Fig. 24). It is slender with elongate anterior and posterior processes. There is a large anterior inferior mylohyoid foramen that is positioned anterodorsal to the smaller anterior mylohyoid foramen. There is a medial shelf that curls dorsally and obscures the anterior mylohyoid foramen in medial view.

Identification

The fossil shares an enclosed anterior inferior alveolar foramen with pleurodontans, teiids, some gymnophthalmoids, and some anguids (Evans 2008; Gauthier et al. 2012; Morales et al. 2019; Fig. 25). Teiinae differ from the fossil and other North American lizards in having an inferior alveolar foramen that is larger and posterodorsally located relative to the anterior mylohyoid foramen (Tedesco et al. 1999; Fisher and Tanner 1970; Gauthier et al. 2012; Fig. 26). Anguids usually have an anterior inferior alveolar foramen that is not entirely enclosed by the splenial, but some individuals have been observed with a completely enclosed foramen (Bochaton et al. 2016b; Ledesma et al. 2021). Many anguids differ from the fossil and pleurodontans in having the posterior end of the splenial bifurcated into a distinct dorsal and ventral process (Ledesma and Scarpetta 2018). There is substantial variation in splenial morphology among gymnophthalmoids. Some gymnopthhalmoids differ from the fossil in having an anteroposteriorly short splenial (Hoyos 1998; Evans 2008; Yanez-Munoz et al. 2021). Other gymnophthalmoids (e.g., Gymnophthalmus speciosus) differ from the fossil in lacking an anterior inferior alveolar foramen fully enclosed within the splenial (Evans 2008). Some gymnophthalmoids (e.g., see fig. 7 of Ptychoglossus vallensis in Morales et al. 2019) resemble the fossil, but are excluded based on geography. The fossil splenial is identified to Pleurodonta.

Figure 25.

Pleurodontan Splenials. Splenials in lateral view– A. Sceloporus clarkii TxVP M-12157; B. Uma exsul TNHC 30247; C. Phrynosoma cornutum TxVP M-6405; D. Phrynosoma douglasii TxVP M-8526; E. Iguana iguana TxVP M-8454; F. Ctenosura hemilopha TxVP M-8616; G. Dipsosaurus dorsalis TxVP M-13086; H. Crotaphytus collaris TxVP M-12468; I. Gambelia sila TNHC 95261; J. Basiliscus vittatus TxVP M-8556; K. Corytophanes sp. TxVP M-16765 L. Leiocephalus carinatus TNHC 89274; M. Leiocephalus psammodromus TNHC 103220; N. Polychrus gutturosus TNHC 24152; O. Enyalioides heterolepis UF 68015. Scale bars = 1 mm.

Figure 26.

Non-Pleurodontan Splenials. Splenials in medial view– A. Coleonyx variegatus TxVP M-12109; B. Scincella lateralis TxVP M-5531; C. Plestiodon gilberti TxVP M-8587; D. Aploglossus plicatus 34481; E. Aspidoscelis sonorae TxVP M-15670; F. Heloderma suspectum TxVP M-9001; G. Xenosaurus grandis TxVP M-8960; H. Diploglossus millepunctatus TxVP M-9010; I. Diploglossus bilobatus TNHC 31933; J. Anniella pulchra TxVP M-8678; K. Ophisaurus attenuatus TxVP M-8979; L. Gerrhonotus infernalis TxVP M-13441; M. Barisia imbricata TNHC 76984. Scale bars = 1 mm.

The splenial of crotaphytids is much more slender and elongate compared to that of the fossil. The prearticular crest in Iguana iguana, Ctenosaura, Dipsosaurus dorsalis, Sauromalus, Corytophanes, and Basiliscus vittatus is flat, whereas it curves dorsally in the fossil and in most examined Sceloporus (except for some Sceloporus jarrovii) such that the anterior mylohyoid foramen is obscured in lateral view. Iguana (Conrad and Norell 2010) and Polychrus marmoratus UF 65135 differ from the fossil in having the anterior inferior alveolar foramen positioned directly dorsal to the anterior mylohyoid foramen. Polychrus gutturosus differs in having a relatively shorter splenial along the posterior half of the bone. The splenials of Leiocephalus and Enyalioides heterolepis differ from the fossil in being relatively longer and more slender. Anolis differs in either lacking a separate and distinct splenial bone or having a short splenial (Etheridge and de Queiroz 1988). Based on these differences with other NA pleurodontans, fossils were assigned to Phrynosomatidae.

Compound bone

Description

Morphotype A: TxVP 41229-27307 serves as the basis for our description and is a right compound bone that is missing the distal end of the prearticular (Fig. 24). The adductor fossa is elongate and open. The retroarticular process narrows posteriorly and is squared off at the posterior end. There is a medially oriented angular process with a lamina of bone connecting the retroarticular and angular processes. There is a medial crest (tympanic crest of McGuire 1996) that extends longitudinally along the dorsal surface of the retroarticular process, and a longitudinal ridge on the ventral surface of the process. The medial process is tall. There is a small crest dorsally on the surangular and a distinct dentary articulation facet on the lateral surface. There are two posterior surangular foramina, one lateral to the medial process and the other slightly ventral, and one anterior surangular foramen lateral to the crest on the surangular. TxVP 41229-26996 is an unusual dermarticular with a lateral notch on the retroarticular process. The margin just lateral to the articular surface is developed into a small boss.

Morphotype B: TxVP 41229-26293 serves as the basis for our description (Fig. 24). TxVP 41229-26293 is a left compound bone that is missing the distal end of the prearticular. The adductor fossa is elongate and open. The retroarticular process is broad and flat. There is a posteromedially-oriented angular process with a low dorsal ridge. There is no distinct medial crest and a ventral ridge on the retroarticular process. The medial process is tall. There is a small crest dorsally on the surangular and distinct dentary articulation facet on the lateral surface.

Identification

Fossils are referred to Pleurodonta based on having a posteriorly directed retroarticular process that is not broadened posteriorly and that is lacking a widely opened adductor fossa (Estes et al. 1988). Polychrus differs from the fossils in having the retroarticular process reduced (Smith 2011). The angular process does not project as far medially in Dipsosaurus dorsalis, Sauromalus, and Iguana iguana compared to the fossils (see also fig. 48 in Smith 2011). The medial crest tends to be more distinct in Dipsosaurus dorsalis, Iguana iguana, Ctenosaura similis, and Enyalioides compared to crotaphytids (Smith 2011). In Laemanctus and Corytophanes, the angular process is shorter compared to the fossils and in Basiliscus basiliscus the medial crest is more distinct and the retroarticular process is thinner (see fig. 71 in Smith 2011). Examined Anolis resemble fossils from Morphotype A in having a distinct angular process connected to the retroarticular process by a sheet of bone but differ in having a horizontally oriented posterior terminus of the retroarticular process. The posterior terminus of the retroarticular process is slightly angled in the fossils, similar to many phrynosomatids (Presch 1969). Additionally, examined Anolis carolinensis (also in A. garmani, see fig 25 in Smith 2011) have a broad depression on the dorsal surface of the surangular just anterior to the articular surface not seen in the fossils. Based on these differences with other NA pleurodontans, fossils were assigned to Phrynosomatidae.

Sceloporinae Savage, 1958

Referred specimens: See Table S3.

Premaxilla

Description

TxVP 41229-29096 and TxVP 41229-27523 serve as the basis for our description (Fig. 27). TxVP 41229-29096 is a premaxilla with six unicuspid, widely spaced teeth. It has a slightly rounded rostral surface and a long nasal process with distinct lateral nasal articulation facets. There is an ossified bridge extending laterally from the nasal process and enclosing the medial ethmoidal foramen on the right side and an incomplete bridge of bone on the left side. There are small foramina just lateral to the base of the nasal process that pierce ventrally. There are shallow maxillary facets laterally on the alveolar plate. Posteriorly, the palatal plate is steeply slanted with distinct vomer articulation facets. The incisive process is short, squared-off, and slightly bilobed. TxVP 41229-27523 differs from TxVP 41229-29096 in having seven tooth positions, a narrow nasal process with a small anterior nasal facet on the left side, and in lacking an ossified bridge.

Figure 27.

Fossil phrynosomatids. TxVP 41229-25618 Anterior view of premaxilla; TxVP 41229-28865 Anterior view of premaxilla; TxVP 41229-29179 Anterior view of premaxilla; TxVP 41229-26026 Posterior view of left quadrate; TxVP 41229-25586 Posterior view of right quadrate; TxVP 41229-29096 Anterior view of premaxilla; TxVP 41229-26977 Anterior view of premaxilla; TxVP 41229-27523 Anterior view of premaxilla; TxVP 41229-27137 Lateral view of left dentary; TxVP 41229-28986 Anterior view of premaxilla; TxVP 41229-27555 Medial view of left maxilla; TxVP 41229-534 Dorsal view of frontal; TxVP 41229-29015 Dorsal view of frontal; TxVP 41229-12032 Anterior and dorsal view of parietal; TxVP 41229-8994 Anterior and dorsal view of parietal; TxVP 41229-25834 Anterior and dorsal view of parietal. Scale bars = 1 mm.

Identification

Premaxillae are assigned to Pleurodonta based on having a fused premaxilla (Estes et al. 1988) with less than seven tooth positions (Smith 2009a). The seven tooth positions of TxVP 41229-27523 overlaps with other NA lizards including scincids, teiids, xantusiids, and Anniella (Evans 2008; Smith 2009a). Scincids differ in having an unfused premaxilla (Gauthier et al. 1988), teiids differ in lacking an incisive process (Gao and Norell 1998; Conrad 2008; Morales et al. 2019), xantusiids differ in having a much thinner nasal process and a broad, flat palatal plate (Savage 1963), and Anniella have a more posteriorly directed nasal process (Toerien 1950; Evans 2008). Among NA pleurodontans, Anolis and Polychrus differ from the fossils in having greater than seven tooth positions (Smith 2011; Daza et al. 2012). Many members of Iguanidae differ in having multicuspid teeth on the premaxilla (de Queiroz 1987). Unicuspid teeth are sometimes found in Ctenosaura, Cyclura and Sauromalus (Scarpetta 2019), but these taxa differ in that the anterior rostral face of the premaxilla in Ctenosaura is distinctly rounded (Scarpetta 2019) and the nasal processes of Ctenosaura, Cyclura, and Sauromalus curve far posteriorly (Scarpetta 2019; Smith 2011). Basiliscus, Corytophanes, and Enyaliodes differ from the fossils in having a broader nasal process (Smith 2009a). Laemanctus differs from the fossils in having a strongly tapering nasal process (Smith 2011). TxVP 41229-29096 differs from examined Crotaphytus in lacking facets on the nasal process in anterior view; however, facets may be absent in some species of Gambelia (Daza et al. 2012). TxVP 41229-27523 has a small anterior nasal facet on the left side but differs from many Crotaphytus in having a more slender nasal process (McGuire 1996). Gambelia differ from the fossils in having longer and sharper teeth and a vertical ridge on the posterior edge of the palatal plate (McGuire 1996). Examined Leiocephalus differ from the fossil in having at least seven tooth positions (see also Bochaton et al. 2021), but Leiocephalus personatus was reported to have six tooth positions (Smith 2009a). Furthermore, examined Leiocephalus differ from the fossils in having a more triangular shaped nasal process that tapers posterodorsally (see also Bochaton et al. 2021). Based on these differences with other NA pleurodontans, fossils were assigned to Phrynosomatidae.

Among phrynosomatids, anterior premaxillary foramina are lacking in Sceloporus, Urosaurus, and Petrosaurus, are present in Uma and Phrynosoma, and are variably present in Callisaurus, Cophosaurus, Holbrookia, and Uta stansburiana (Scarpetta 2019). Some Sceloporus (e.g., S. orcutii) have an ossified bridge extending laterally from the nasal process and enclosing the medial ethmoidal foramen, but these foramina, when present, are positioned farther dorsolaterally compared to the anterior premaxillary foramina in other phrynosomatids. Sand-lizards (Callisaurus, Cophosaurus, Holbrookia, and Uma) typically have a flat rostral face of the premaxilla, while sceloporines (Sceloporus, Urosaurus, Petrosaurus, and Uta) have a more rounded rostral face (Scarpetta 2019). Fossil premaxillae are assigned to Sceloporinae on that basis.

Quadrate

Description

TxVP 41229-27058 and TxVP 41229-26983 serve as the basis for our description (Fig. 22). TxVP 41229-27058 is a left quadrate. There is a thin, medially slanted central column, and the bone narrows ventrally. There is a moderately developed medial crest but no pterygoid lappet. The conch is deep and gradually slants laterally from the central column. The cephalic condyle projects posteriorly without extensive dorsal ossification and the condyle has a small dorsal tubercle. The dorsolateral margin of the tympanic crest is rounded. There is a foramen on the anteroventral surface (quadrate foramen of Villa and Delfino 2019), and a small hole on the dorsal margin of the conch that may be a taphonomic alteration. TxVP 41229-26983 differs from TxVP 41229-27058 in having a dorsal margin that slopes ventrolaterally in a step-like fashion.

Identification

Fossil quadrates are differentiated from NA lizards except for pleurodontans based on the absence of a pterygoid lappet (Estes et al. 1988; Evans 2008), having a wide central column (Kluge 1962; Evans 2008), and having the dorsal portion much wider compared to the articular surface (see crotaphytid section above for additional discussion on identifying quadrates to Pleurodonta). Among NA pleurodontans, in Anolis and Polychrus the lateral and medial margins are more parallel compared to the fossils. Additionally, in Anolis there is a distinct boss at the ventromedial margin of the quadrate not seen in the fossils. The quadrate of Basiliscus basiliscus, Corytophanes, and Laemanctus is proportionally taller relative to its width compared to the fossils. The quadrate of Enyalioides heterolepis has a more shallow conch and straighter lateral margin (tympanic crest) compared to the fossils. Ctenosaura, large Iguana, and Leiocephalus differ from the fossils in having a pterygoid lamina that extends farther medially. The quadrate of small Iguana is much more slender than the fossils. The quadrates of most Sauromalus have a ventrolaterally slanted dorsolateral margin, resembling TxVP 41229-26983, but differ in having a distinct dorsomedial expansion at the dorsal margin of the pterygoid lamina (Evans 2008). Some examined Sceloporus (S. olivaceous TxVP M-8375 and S. orcutti TxVP M-12155) also have a ventrolaterally slanted dorsolateral margin. Crotaphytids differ from the fossils in having a straight lateral margin (tympanic crest) (Mead 1988). Based on these differences with other NA pleurodontans, quadrates were assigned to Phrynosomatidae. The quadrate of phrynosomatines (except for Uma and Phrynosoma) differs from the fossils in having a very shallow conch (Evans 2008) and a strongly curved medial edge, including a medially curved central column. Uma and Phrynososma differ from the fossils in having a straight lateral margin (tympanic crest) (Mead 1988). Based on these differences fossils were assigned to Sceloporinae.

Urosaurus Hallowell, 1854

Referred specimens: See Table S3.

Dentary

Description

TxVP 41229-27603 is a left dentary with 25 tooth positions (Fig. 27). Distal teeth are weakly tricuspid and slender. The Meckelian groove is fused for about 12 tooth positions and opens at the anterior end of the dentary. The dental shelf is narrow, but widens slightly anteriorly. There is a small intramandibular lamella. The posterior end bears a distinct surangular and angular process and there is a coronoid facet within a dorsally projecting corner of bone (coronoid process). There are four nutrient foramina on the anterolateral surface. TxVP 41229-27137 is missing the anterior and posterior ends. In TxVP 41229-27137, the Meckelian groove is fused for nine tooth positions.

Identification

Fossil dentaries share with Pleurodonta, Xantusiidae, and some gymnophthalmoids pleurodont tricuspid teeth and a fused Meckelian groove (Evans 2008; Scarpetta 2021). Xantusiids differ in having a fused spleniodentary (Savage 1963; Mead and Bell 2001; Evans 2008). In gymnophthalmoids with tricuspid teeth and a fused Meckelian groove, the groove is completely fused to almost the level of the posterior-most tooth position (Bell et al. 2003). Among NA pleurodontans, the fossils share with some phrynosomatids, iguanids, dactyloids, extant Leiocephalus, polychrotids, and some corytophanids a fused Meckelian groove (Smith 2011; Scarpetta 2021). Fossils differ from these taxa, except for some phrynosomatids, in having weakly tricuspid teeth. Additionally, iguanids, Leiocephalus, Basiliscus, Corytophanes, and some Laemanctus differ from fossils in having flared tooth crowns (Smith 2009a; Scarpetta 2021) and Polychrus differ in having labial and lingual striations on the teeth (Smith 2009a). On this basis, fossils were identified to Phrynosomatidae. Among phrynosomatids, having a fused Meckelian groove and weakly tricuspid teeth is a combination of features only found among Urosaurus (Mead et al. 1985; Scarpetta 2021). A fused Meckelian groove is occasionally present in other phrynosomatids (e.g., Petrosaurus mearnsi TxVP M-14910); but the teeth have more prominent accessory cusps.

Phrynosomatinae Wiens et al. 2010

Callisaurini “sand lizards” (Callisaurus, Cophosaurus, Holbrookia, and Uma) Wiens et al. 2010

Referred specimens: See Table S3.

Premaxilla

Description

TxVP 41229-29179 serves as the basis for our description (Fig. 27). TxVP 41229-29179 is a premaxilla with seven tooth positions and unicuspid teeth. It has a flat rostral surface with two anterior premaxillary foramina. The long, thin nasal process is missing the distal tip. There is a ventral keel separating the nasal facets. There are small foramina posteriorly on the palatal shelf. There are indistinct maxillary facets laterally on the alveolar plate. Posteriorly, the palatal plate is short and steeply slanted. The incisive process is minute and narrow. TxVP 41229-28865 has eight tooth positions.

Identification

Fossil premaxillae share with some pleurodontans, some amphisbaenians, some anguimorphs (Ophisaurus, gerrhonotines, and xenosaurids) anterior premaxillary foramina (Smith 2009b; Bhullar 2011; Scarpetta 2019). Examined amphisbaenians differ in having an enlarged median tooth (Smith 2009b). Anguimorphs differ from the fossils in having a more distinctly bilobed and elongate incisive process (Evans 2008). Furthermore, Xenosaurus differ in having a rugose rostral surface of the premaxilla (Bhullar 2011). Fossils are assigned to Pleurodonta.

Among NA pleurodontans, crotaphytids and Leiocephalus differ in lacking anterior premaxillary foramina (Smith 2009a). The South American hoplocercid Enyalioides oshaughnessyi was reported to have anterior premaxillary foramina (Smith 2009a), but they are absent in examined E. heterolepis. Many iguanids differ from the fossils in having multicuspid teeth on the premaxilla (de Queiroz 1987), and the remaining iguanids differ in having a rounded anterior rostral face of the premaxilla (Scarpetta 2019). Anolis, Polychrus, and corytophanids also differ from the fossils in having a more rounded anterior rostral face of the premaxilla (see also Smith 2011). Furthermore, Basiliscus, Corytophanes, and Enyalioides differ from the fossils in having a broader and parallel-sided nasal process (Smith 2009a, b). Based on differences with other NA pleurodontans, fossils were identified to Phrynosomatidae.

Among phrynosomatids anterior premaxillary foramina are known in Uma, Phrynosoma, Callisaurus, Cophosaurus, Holbrookia, and Uta stansburiana (Scarpetta 2019). Uta differs from phrynosomatines in having a rounded rostral face of the premaxilla (Scarpetta 2019). Fossils premaxillae are assigned to Phrynosomatinae based on the presence of anterior premaxillary foramina and a flat anterior rostral face of the premaxilla. Among phrynosomatines, Phrynosoma differs from sand-lizards in having a nasal process that is directed dorsally and a nasal process that at its base is as wide as the body of the premaxilla (Montanucci 1987; Scarpetta 2019). Premaxillae are assigned to the sand lizard clade based on having a nasal process that is directed posterodorsally and a nasal process that is narrower than the body of the premaxilla. The premaxilla of Uma differs from other sand-lizards in having a nasal process that resembles an isosceles triangle. Fossil premaxillae lack that morphology and so fossils likely represent Callisaurus, Cophosaurus, or Holbrookia.

Quadrate

Description

TxVP 41229-26026 is a left quadrate (Fig. 27). The central column is indistinct, curves medially, and has a distinct medial groove. The bone narrows ventrally and there is no pterygoid lappet nor medial crest. The conch is shallow. The cephalic condyle projects posteriorly without extensive ossification dorsally. The dorsolateral margin of the tympanic crest is rounded. There is an anteriorly slanted dorsal tubercle. TxVP 41229-25586 differs in having an ossified squamosal foramen and having a dorsal surface with two depressions separated by a slanted medial ridge.

Identification

Fossils share the absence of a distinct pterygoid lappet with geckos, Scincella, Xantusia, some pleurodontans, and anguimorphs beside Heloderma (Estes et al. 1988; Evans 2008). Geckos, Xantusia, Scincella, and anguimorphs differ from the fossils in lacking a quadrate that widens dorsally. On this basis the fossil was identified to Pleurodonta. Among NA pleurodontans, the fossils share the absence of a well-developed pterygoid lamina (medial conch of Smith 2009a) with Anolis, Polychrus, Corytophanes, Laemanctus, and some phrynosomatines (Lang 1989; Smith 2009a). Corytophanids and Polychrus differ in having a low ridge within the lateral concha (Smith 2009a). Anolis differs in having a distinct boss at the ventromedial margin of the bone below the articulation with the pterygoid. The fossils share with phrynosomatines (except for Uma and Phrynosoma) a very shallow conch (Evans 2008) and a strongly curved medial edge, including a medially curved central column. This combination of features is unique to sand lizards among NA pleurodontans. Fossils are assigned to the sand lizard clade on this basis. The quadrate of Xenosaurus grandis also has a shallow conch strongly curved medial edge but differs from phrynosomatines in having an expanded medial pterygoid lamina and a proportionally wider mandibular condyle.

Phrynosomatidae Fitzinger, 1843

Morphotype A: TxVP 41229-534 serves as the basis for our description (Fig. 27). TxVP 41229-534 is a frontal with two posterolateral processes on either side, each with a small anteriorly projecting anterior superciliary process (sensu Montanucci 1987). The frontal is dorsoventrally tall near the base of the posterolateral processes. There are many tall, peaked tubercles on the dorsal surface beginning midway at the interorbital region and posterior. There are long superciliary horns on the posterolateral process. Anteriorly, there are bilateral facets for articulation with the nasal and prefrontal. The cristae cranii do not project far ventrally. There is a small midline notch on the posterior edge of the bone, and posterolaterally there are deep parietal facets.

Morphotype B: TxVP 41229-29015 serves as the basis for our description (Fig. 27). The fossil is mostly complete but is missing the distal end of the right posterolateral process and the left prefrontal and nasal facets. The bone is tall near the base of the posterolateral processes. The left posterolateral process has a small anteriorly projecting anterior superciliary process. There are low rounded tubercles posteriorly on the dorsal surface, and the superciliary horns on the posterolateral process are short. Anteriorly, there is a facet for articulation with the nasal and prefrontal. The cristae cranii are short and anteriorly border a deep depression on the ventral surface.

Identification

Fossils share with Pleurodonta and Teiioidea a fused frontal with reduced cristae cranii (Estes et al. 1988). Fossils differ from all other NA lizards, except for Phrynosoma, in having a supraorbital process extending anteriorly from each posterolateral portion of the frontal (Presch 1969). Fossils are assigned to Phrynosoma on that basis. A major difference between frontals of morphotype A and B is the morphology of the ornamentation. Fossils of both morphotypes differ from Phrynosoma asio, which has a smooth dorsal surface, and from P. mcallii which has dorsal tubercles over nearly the entire length of the frontal (Montanucci 1987).

Morphotype A: Fossils of morphotype A most closely resemble species including P. cornutum, P. modestum, P. platyrhinos, P. goodei, P. coronatum (reportedly variable; Montanucci 1987), P. blainvillii, P. cerroense, P. ditmarsi, P. taurus, P. braconnieri, and P. obiculare in having peaked tubercles on the posterolateral process (Montanucci 1987). Phrynosoma modestum, P. platyrhinos, and P. goodei differ from the fossils in having relatively shorter superciliary horns (see fig. 1 in Powell et al. 2017). Furthermore, P. modestum differs in having an anterolaterally-oriented supraorbital process. Phrynosoma coronatum, P. blainvillii, P. cerroense, P. ditmarsi, P. modestum, P. platyrhinos, and P. obiculare differ from the fossils in having relatively shorter tubercles and peaked tubercles largely restricted to the posterolateral process (Montanucci 1987; Powell et al. 2017). The peaked tubercles appear to be shorter in P. braconnieri compared to fossils, while P. taurus has longer superciliary horns (Powell et al. 2017). The fossils most closely resemble P. cornutum; however, we did not examine several species of Phrynosoma (e.g., P. sherbrookei), so we do not make a species or infrageneric identification.

Morphotype B: Fossils of morphotype B differ from morphotype A in having low rounded tubercles posteriorly on the dorsal surface, as in species in the P. douglasii species complex (Montanucci 1987). It was previously suggested that several fossil frontals may represent P. modestum (Toomey 1993). However, P. modestum has shorter superciliary horns and more distinctively rugose tubercles compared to the fossils and examined species in the P. douglasii species complex.

Parietal

Description

Morphotype A: TxVP 41229-8994 serves as the basis for our description (Fig. 27). The fossil is nearly complete, only missing the distal end of the left lateral horn and the left postparietal process. The parietal table is rectangular with distinct anterolateral processes. The anterior edge has deep, bilateral facets for the frontal. The dorsal surface is covered in long tubercles. The right posterolateral parietal horn is long and there is a small horn between the main posterolateral horns. The posterior edge between the postparietal processes is characterized by two depressions (nuchal fossae) separated by a small midline posterior projection. The right postparietal process is short and projects posteroventrally and bears a lateral facet for the squamosal and a medial facet for the paroccipital process of the exoccipital. The ventrolateral crests are low without distinct epipterygoid processes. On the ventral surface, there are shallow depressions (cerebral vault) divided by a low ridge. There is no pit for the processus ascendens.

Morphotype B: TxVP 41229-25834 serves as the basis for our description (Fig. 27). TxVP 41229-25834 is a parietal missing the left posterolateral portion and the right postparietal process. The parietal table is rectangular. The anterior edge has a small midline notch between deep, bilateral facets for the frontal. The dorsal surface is covered in rounded tubercles. The right posterolateral parietal horn is short. The lateral surface has a deep depression for articulation with the squamosal. The posterior edge between the postparietal processes is characterized by two depressions (nuchal fossae) separated by a small midline posterior projection. The ventrolateral crests are low without distinct epipterygoid processes. On the ventral surface there are shallow depressions (cerebral vault) divided by a low ridge. There is no pit for the processus ascendens.

Identification

The broad, rectangular shape of the parietal and the presence of posterolateral dorsal horns differentiate Phrynosoma from those of all other North American lizards (Presch 1969). Fossils were identified to Phrynosoma on that basis.

Morphotype A: The length of the parietal horns varies among extant Phrynosoma. Fossil parietals of morphotype A have long lateral parietal horns, a small medial horn, and long dorsal bony tubercles. The length of the lateral horns of morphotype A is similar to P. cornutum, P. solare, P. mcallii, P. platyrhinos, P. goodei, P. blainvillii, P. cerroense, and P. coronatum (Norell 1989; Parmley and Bahn 2012; see also fig. 1 in Powell et al. 2017). It was previously suggested that a few fossil parietals (e.g., TxVP 41229-12032) may represent P. modestum (Toomey 1993); however, P. modestum, P. obiculare, P. braconnieri, and P. asio have slightly shorter lateral horns, and P. modestum and P. asio lack the long dorsal tubercles present in morphotype A (Mead et al. 1985; Montanucci 1987; Parmley and Bahn 2012). Additionally, P. modestum lacks a small medial horn, similar to P. asio and some P. platyrhinos (Presch 1969; Norell 1989). Phrynosoma mcallii differ from the fossils in having short dorsal tubercles, and P. solare differs in having four well developed parietal horns (Montanucci 1987). The long dorsal tubercles present in fossil parietals are similar to P. cornutum, P. coronatum, P. solare, P. blainvillii, P. cerroense, P. braconnieri, and P. orbiculare, but the latter two species have shorter parietal horns compared to the fossils. Based on those features, fossils are most similar to P. cornutum, P. coronatum, P. blainvillii, and P. cerroense.

Morphotype B: Fossil parietals of morphotype B have short lateral horns with no medial horn and rounded tubercles on the dorsal surface. The short lateral horns of morphotype B are similar to P. taurus and species in the P. douglasii species complex (Montanucci 1987; Norell 1989; Parmley and Bahn 2012). The tubercles in P. taurus are more numerous and pointed compared to the fossils (see fig. 1 in Powell et al. 2017) and the closely related P. sherbrookei has longer parietal horns (Nieto-Montes de Oca et al. 2014). Fossils are most similar to species in the P. douglasii species complex.

Prefrontal

Description

Morphotype A: TxVP 41229-27205 is a left prefrontal that serves as the basis for our description (Fig. 28). It is triradiate with a small anterior orbital process, a long posteromedial process, and a long supraorbital process. The supraorbital process thins distally and curves medially. The medial surface is characterized by deep articulation facets for the frontal posteriorly and the maxilla anteriorly. Dorsal to the frontal facet, there is a small groove for the nasal articulation. The dorsal surface has several distinct tubercles. The ventral surface is smooth, concave, and has a small anterior foramen.

Figure 28.

Fossil phrynosomatids. TxVP 41229-27205 Dorsal view of left prefrontal; TxVP 41229-26214 Dorsal view of left prefrontal; TxVP 41229-799 Lateral view of left jugal; TxVP 41229-26220 Lateral view of left jugal; TxVP 41229-27368 Lateral and posterior view of postorbital; TxVP 41229-27225 Anterior view of squamosal; TxVP 41229-25835 Anterior view of squamosal; TxVP 41229-25903 Posterior view quadrate; TxVP 41229-27134 Lateral and medial view of dentary; TxVP 41229-28744 Lateral and medial view of dentary; TxVP 41229-27341 Lateral and medial view of coronoid; TxVP 41229-10024 Dorsal view of compound bone; TxVP 41229-26299 Dorsal and lateral of compound bone. Scale bars = 1 mm.

Morphotype B: TxVP 41229-26214 is also a left prefrontal that serves as the basis for our description (Fig. 28). It is triradiate and the processes are nearly the same length. The anterior orbital process is notched at the anterior end for passage of the lacrimal foramen. The supraorbital process is directed posterolaterally and is relatively straight. The dorsal surface has a few low, round tubercles. The ventral surface is smooth, concave, and has a small foramen medially.

Identification

The prefrontal of Phrynosoma is distinct from nearly all NA lizards (except for Corytophanes) in having a long supraorbital process that extends posteriorly to partially or fully enclose the supraorbital fenestra (Presch 1969; Lang 1989). The prefrontal of Corytophanes differs from that of Phrynosoma in having a deep depression on the lateral surface of the bone. Fossils were identified to Phrynosoma on that basis.

Morphotype A: Fossils of morphotype A have a long supraorbital process that curves medially. A long supraorbital process also occurs in P. cornutum, P. mcallii, P. solare, P. taurus, P. asio, and somewhat in P. braconnieri (Montanucci 1987; Powell et al. 2017). The supraorbital process of P. solare appears to be relatively longer compared to the fossils and other species of Phrynosoma (Montanucci 1987; Powell et al. 2017).

Morphotype B: Fossils of morphotype B have a shorter supraorbital process that is straighter. A short supraorbital process also occurs in P. coronatum, P. cerroense, P. blainvilli, P. ditmarsi, P. modestum, P. obiculare, P. platyrhinos, and species in the P. douglasii species complex (Montanucci 1987; Powell et al. 2017). P. modestum differs from the fossil in having a more distinctly rugose surface and having a large anterior notch.

Jugal

Description

Morphotype A: TxVP 41229-799 is a left jugal (Fig. 28). The anterior orbital process is thin with a ventral maxillary articulation facet. The postorbital process is broad, is directed posterodorsally, and has a distinct anterior postorbital articulation facet. The lateral surface of the postorbital process has a row of three long tubercles. The medial surface is smooth, and there is a depression on the postorbital process. There is a foramen on the lateral surface near the inflection point.

Morphotype B: TxVP 41229-26220 serves as the basis for our description and is a well preserved left jugal (Fig. 28). TxVP 41229-26220 differs from morphotype A in having the anterior orbital process widened relative to the postorbital process, a broad, flat posterodorsal surface in lateral view, and the lateral surface of the postorbital process has a row of several low, rounded tubercles.

Identification

Fossil jugals share with Phrynosoma, Anolis, Corytophanes, Lepidophyma, and Xantusia riversiana an expanded postorbital process (Savage 1963; Montanucci 1987; Lang 1989; Smith 2011). Anolis differs in having a relatively less expanded postorbital process (Smith 2011). Fossil jugals differ from Anolis, Corytophanes, Xantusia riversiana, and Lepidophyma in having a more posteriorly oriented postorbital process (Savage 1963; Smith 2011; Lang 1989). Fossils were identified to Phrynosoma.

Morphotype A: Fossils of morphotype A have a row of long tubercles on the lateral surface. This is similar to the condition described for P. ditmarsi, P. coronatum, P. solare, P. cornutum, P. modestum, P. mcallii, and P. platyrhinos (Montanucci 1987). Phrynosoma braconnieri, P. taurus, P. obiculare, P. douglassi, and P. hernandesi have lower and more rounded tubercles compared to the fossils (Montanucci 1987). We were unable to examine this feature in all species of Phrynosoma and do not make species level identifications.

Morphotype B: Fossils of morphotype B share with P. orbiculare and species in the P. douglasii species complex a broad, flat posterodorsal surface in lateral view (Montanucci 1987). Fossils of morphotype B also have a row of several low, rounded tubercles. This is similar to the condition described for P. taurus, P. braconnieri, and species in the P. douglasii species complex. Phrynosoma taurus and P. braconnieri differ in having more triangular shaped jugals (Montanucci 1987). Phrynosoma orbiculare also has low, rounded tubercles anteriorly, but may have a more distinct posterior tubercle (Montanucci 1987). The fossils are similar to species in the P. douglasii species complex, but we were unable to examine features on the jugal for all species of Phrynosoma making this identification tentative.

Postorbital

Description

TxVP 41229-27368 serves as the basis for our description and is a right postorbital (Fig. 28). The dorsal process widens mediolaterally, and projects anteriorly with a lateral facet for articulation with the frontal and parietal. Laterally, the postorbital is twisted with a long, ventrally pointed process. Posterolaterally, there is a squamosal articulation facet, and the lateral margin has a groove for articulation with the jugal. The dorsal surface has several long tubercles. Ventrally there is a ridge that runs from the posteromedial corner onto the ventrolateral process.

Identification

Postorbitals were identified to Pleurodonta based on a sub-triangular morphology with a distinct ventral process (Estes et al. 1988). Among NA pleurodontans, a broadened dorsal process is found in Phrynosoma, Iguana iguana, and Corytophanes (Presch 1969; Lang 1989; Evans 2008). The dorsal process in examined Iguana iguana is not expanded to the extent seen in the fossils. The postorbital of Corytophanes differs in having an anteriorly projecting spine extending from the dorsal process that contacts the prefrontal (Lang 1989). On this basis fossils were identified to Phrynosoma. The fossils share with P. solare, P. braconnieri, P. cornutum, P. coronatum, P. ditmarsi, P. mcallii, P. modestum, P. obiculare, P. platyrhinos, and P. taurus a rugose lateral surface with distinct tubercles (Montanucci 1987). Phrynosoma mcallii differs in having a posteriorly expanded postorbital that restricts the supratemporal fossa (Norris and Lowe 1951).

Squamosal

Description

Morphotype A: TxVP 41229-27225 is a right squamosal that serves as the basis for our description (Fig. 28). The anterior edge is concave with a posteromedial process that is broken at the distal end. The dorsal surface has two long medial horns and one short lateral horn. There is a short posteroventrally projecting inferior process (sensu Powell et al. 2017) with a lateral facet for the supratemporal.

Morphotype B: TxVP 41229-25835 is a left squamosal missing the posteromedial process and a portion of the anterior edge (Fig. 28). The dorsal surface has two short medial horns and one minute lateral horn. Posteriorly, there is a short posteroventraly projecting inferior process with a lateral facet for the supratemporal.

Identification

The squamosal of Phrynosoma is unique among North American lizards in having horns along the dorsal surface (Presch 1969). Fossils were identified to Phrynosoma.

Morphotype A: The number and length of the squamosal horns varies among extant Phrynosoma. The number of horns was previously considered to be of limited diagnostic use because of considerable overlap between extant species (Presch 1969; Bell 1993) and because fossils are often broken, so exact horn number is often indeterminate. Fossil squamosals of morphotype A have long horns similar to P. cornutum, P. modestum, P. asio, P. coronatum, P. mcallii, P. platyrhinos, and P. solare (Parmley and Bahn 2012). Phrynosoma asio differs in only having two horns and P. solare has four (Montanucci 1987; Bell 1993). Phrynosoma modestum differs in having a long posterior horn and shorter anterior horns (Parmley and Bahn 2012).

Morphotype B: Fossil squamosals of morphotype B have short horns. The short lateral horns are similar to P. braconnieri, P. ditmarsi, and species in the P. douglasii species complex (Parmley and Bahn 2012; Powell et al. 2017). Phrynosoma braconnieri and P. ditmarsi differ in having a relatively broader squamosal in dorsal view (Powell et al. 2017). Fossils are most similar to species in the P. douglasii species complex.

Quadrate

Description

TxVP 41229-25903 serves as the basis for our description and is a left quadrate (Fig. 28). There is a wide, medially slanted central column, and the bone narrows ventrally. There is no pterygoid lappet, and the medial crest is minute. The conch is deep and is obscured from view at its dorsomedial margin by the central column. The cephalic condyle projects posteriorly without extensive dorsal ossification. The dorsolateral margin of the tympanic crest is slightly rounded. The anterior surface is convex. There is a foramen on the anteroventral surface (quadrate foramen of Villa and Delfino 2019) and a foramen medial to the central column.

Identification

Fossil quadrates were identified to Pleurodonta based on the absence of a pterygoid lappet (Estes et al. 1988) and widening dorsally relative to the articular surface. The quadrate of Phrynosoma (except P. modestum and P. mcallii) differs from other pleurodontans in having a conch that is deep and obscured from view at its dorsomedial margin by the central column. In examined P. modestum and P. mcallii the conch is shallow. The fossil shares with P. cornutum, P. coronatum, P. mcallii, P. modestum, P. platyrhinos, and P. solare a minute medial crest (Presch 1969).

Dentary

Description

Morphotype A: TxVP 41229-27134 serves as the basis for our description and is a left dentary with 19 tooth positions (Fig. 28). Teeth are unicuspid and slender. The Meckelian groove is open medially for its entire length, and the dentary is tall posteriorly. The suprameckelian lip is short anteriorly. The dental shelf is narrow and there is an intramandibular lamella. The posterior end of the dentary is bifurcated. The angular process is broken at the distal end but is flat ventrally and curves far medially. There is a small lateral tubercle at the base of the angular process. There are seven nutrient foramina on the anterolateral surface.

Morphotype B: TxVP 41229-28744 serves as the basis for our description and is a right dentary with 20 tooth positions (Fig. 28). Teeth are unicuspid and slender. The suprameckelian and inframeckelian lips meet midway along the tooth row, and the dentary is tall posteriorly. The suprameckelian lip is short anteriorly. The dental shelf is narrow. The angular process is flat ventrally and curves far medially. The lateral surface is smooth and lacks tubercles, and there are five nutrient foramina anteriorly.

Identification

Morphotype A: Dentaries of Morphotype A share with Pleurodonta and some teiids pleurodont teeth and an inframeckelian lip that curls dorsolingually, producing a medial exposure of the Meckelian groove along the mid-length of the dentary (Gauthier et al. 2012; Bochaton et al. 2017). Fossil dentaries differ from teiids in lacking a broad subdental shelf (Estes et al. 1988), lacking asymmetric bicuspid teeth, and lacking large amounts of cementum deposits at base of teeth (Estes et al. 1988; Nydam et al. 2007; Scarpetta 2020). Fossils are assigned to Pleurodonta. Phrynosoma differ from other NA pleurodontans in having unicuspid teeth (except for some slightly tricuspid posterior teeth in P. asio, P. coronatum, and P. mcallii; Presch 1969), a relatively flat posteroventral surface, and a posteroventral lamina of bone that is curved far medially (Mead et al. 1999). Fossils are assigned to Phrynosoma on this basis. Fossils of morphotype A share with P. asio, P. cornutum, P. mcallii, P. modestum, and P. platyrhinos an open Meckelian groove (Presch 1969). Of those species, P. asio differs in having a smooth lateral surface (Presch 1969; Mead et al. 1999). Phrynosoma modestum was reported to have a smooth lateral surface by Presch (1969); however, other authors note that P. modestum has a rugose lateral surface (Montanucci 1987; Mead et al. 1999; Parmley and Bahn 2012), which is supported by our observations.

Morphotype B: Dentaries of Morphotype B share with Pleurodonta, some teiids, and some scincids pleurodont teeth and suprameckelian and inframeckelian lips that meet to close the Meckelian groove (Greer 1974; Gauthier et al. 2012; Bochaton et al. 2017; Scarpetta 2021). Fossil dentaries differ from teiids and scincids in lacking a broad subdental shelf (Estes et al. 1988) Fossils further differ from teiids in lacking asymmetric bicuspid teeth and lacking large amounts of cementum deposits at base of teeth (Estes et al. 1988; Nydam et al. 2007; Scarpetta 2020). Fossils are assigned to Pleurodonta. Fossils of morphotype B share a closed Meckelian groove with P. braconnieri, P. coronatum, P. orbiculare, P. solare, and species in the P. douglasii species complex (Presch 1969). We also observed one specimen of P. modestum (TxVP M-14818) with a closed Meckelian groove. Phrynosoma solare and examined P. modestum differ in having a rugose lateral surface of the dentary (Presch 1969; Montanucci 1987).

Coronoid

Description

TxVP 41229-27341 is a left coronoid (Fig. 28). The coronoid process is tall and wide, and gradually declines anteriorly, giving the coronoid a triangular appearance. The anteromedial process is elongated, with a medial articulation facet for the dentary, and a small ventrally-projecting lamina of bone. The posteromedial process is thin and directed posteroventrally. There is a distinct medial crest that extends from the coronoid process onto the posteromedial process. There is a small, rounded lateral process. There is a vertically oriented lateral crest that terminates at the posterior margin of the lateral process. The dorsal articulation facet for the surangular is narrow. TxVP 41229-26885 and TxVP 41229-25848 differ in having lateral crests that end anteriorly on the lateral process.

Identification

Fossil coronoids share with several pleurodontans and xantusiids the absence of a distinct anterolateral process (Estes et al. 1988). Xantusiids differ in having an anterior groove extending onto the coronoid process (Savage 1963). Fossils differ from examined NA pleurodontans, except for some Phrynosoma (see fig. 4 in Meyers et al. 2006), in having a triangular-shaped coronoid process that is sloped at a low angle anteriorly. Furthermore, fossils differ from examined NA pleurodontans, except for some Phrynosoma (e.g., P. cornutum TxVP M-6405 and P. douglasii TxVP M-8526), in having a thin, posteriorly directed posteromedial process. Fossils were assigned to Phrynosoma. Fossils differ from P. braconnieri, P. mcallii, and P. solare in having a lateral process to overlap the dentary and surangular (Presch 1969). Examined P. coronatum, P. ditmarsi, P. orbiculare, and P. hernandesi differ in having a more steeply sloped anterior margin of the coronoid process (see fig. 4 of Meyers et al. 2006).

Compound bone

Description

Morphotype A: TxVP 41229-10024 is a left compound bone missing the prearticular and the anterior end of the surangular that serves as the basis for our description (Fig. 28). There is a broad articular surface. The retroarticular process (post-condylar process of Presch 1969) is mediolaterally flat, tall, and oriented in a near vertical plane. The posteroventral end of the retroarticular process is rounded and extends posterior to the dorsal portion. On the surangular there are three lateral horns. The posterior-most horn is long and narrow, and the other horns are short and broad.

Morphotype B: TxVP 41229-26299 serves as the basis for our description and is a right compound bone that is missing the prearticular (Fig. 28). There is a broad articular surface and a short medial process. The retroarticular process is mediolaterally flat and slanted ventrolaterally with a rounded lateral end. The lateral surface of the surangular is smooth, the dorsal margin has a dorsally expanded crest where it articulates with the coronoid, and the ventral margin is slightly convex. There is a posterior surangular foramen and an anterior surangular foramen on the lateral surface.

Identification

The compound bone of Phrynosoma is unlike that of other North American lizards in having a retroarticular process that is twisted in a near vertical plane with dorsal and ventral tubercles on the posterior end (Presch 1969). Fossils were assigned to Phrynosoma on that basis.

Morphotype A: Fossils of morphotype a share with P. cornutum, P. ditmarsi, P. modestum, P. mcallii, P. platyrhinos, P. goodei, and P. solare horns on the lateral surface (Presch 1969; Montanicci 1987). Phrynosoma ditmarsi differs in having the horns oriented more ventrally (Montanicci 1987; see also fig. 4 in Meyers et al. 2006). Phrynosoma modestum differs in having shorter horns relative to the fossils, and P. platyrhinos and P. solare differ in only having two lateral horns (Presch 1969). Fossils have a comparable horn morphology to P. cornutum and P. mcallii.

Morphotype B: Fossils of morphotype B have a flat lateral surface without horns, similar to that in P. asio, P. cerroense, P. coronatum, P. orbiculare, P. taurus, P. braconnieri, and species in the P. douglasii species complex (Presch 1969).

Anguimorpha Fürbringer, 1900

Anguidae Gray, 1825

Referred specimens: See Table S3.

Coronoid

Description

TxVP 41229-27599 is a left coronoid (Fig. 29). The coronoid process is tall, broad, and rounded. The anteromedial process is elongate, but the distal end is missing. The anteromedial process has a medial splenial facet that, with the anteriorly projecting lateral process, forms a narrow facet for the coronoid process of the dentary. The posteromedial process is missing the distal end, but the remaining portion is posteroventrally directed with an expanded posterior lamina of bone to articulate medially with the surangular. The medial crest extends from the coronoid process onto the posteromedial process. There is a vertically oriented lateral crest that ends at the posterior margin of the lateral process. The anteromedial process has a notch, which may convey a foramen.

Figure 29.

Fossil anguids. TxVP 41229-27657 Dorsal and ventral view of premaxilla; TxVP 41229-27438 Lateral and medial view of right maxilla; TxVP 41229-26858 Lateral and medial view of right jugal; TxVP 41229-27659 Medial view of right dentary; TxVP 41229-27599 Lateral and medial view of left coronoid; TxVP 41229-27094 Dorsal and ventral view of right compound bone. Scale bars = 1 mm.

Identification

The fossil coronoid differs from xantusiids and some pleurodontans in having an anterolateral process (Estes et al. 1988; Fig. 30). The fossil differs from examined NA pleurodontans with an anterolateral process (see above) in having a more posteriorly oriented posteromedial process.

Figure 30.

Non-Pleurodontan Coronoid bones. Coronoids in lateral view– A. Anelytropsis papillosus UF 86708; B. Coleonyx varegatus TxVP M-13892; C. Scincella lateralis TxVP M-4489; D. Plestiodon gilberti TxVP M-8587; E. Xantusia riversiana TxVP M-8505; F. Xantusia virigatus TxVP M-12130; G. Lepidophyma lowei LACM 143367; H. Aploglossus plicatus TNHC 34481; I. Aspidoscelis sonorae TxVP M-15670; J. Bipes canaliculatus CAS 134753; K. Heloderma suspectum TxVP M-9001; L. Xenosaurus grandis TxVP M-8960; M. Diploglossus bilobatus TNHC 31933; N. Anniella pulchra TxVP M-8678; O. Ophisaurus ventralis TxVP M-8585; P. Ophisaurus attenuatus TxVP M-8979; Q. Gerrhonotus infernalis TxVP M-13441; R. Barisia imbricata TNHC 76984. Scale bars = 1 mm.

TxVP 41229-27599 differs from examined Aspidoscelis and Ameiva in lacking a deeply notched posterior edge, forming dorsal and ventral rami (Tedesco et al. 1999). Furthermore, Aspidoscelis, Ameiva, and Pholidoscelis differ in having a distinct lateral crest running from the apex of the coronoid process anteroventrally onto the anterolateral process (Tedesco et al. 1999; Bochaton et al. 2019). Fossils differ from gymnophthalmoids in having a relatively shorter anterolateral process (Bell et al. 2003; Roscito and Rodrigues 2010; Morales et al. 2019). North American geckos such as Coleonyx variegatus, C. brevis, Sphaerodactylus roosevelti, and Thecadactylus rapicauda differ from the fossil in having a thinner posteromedial process (Kluge 1962; Daza et al. 2008; Bochaton et al. 2018). The posteromedial process is slightly wider in C. elegans and C. mitratus compared to other species (Kluge 1962) but examined Coleonyx, including C. elegans, have a coronoid process sloped at a posteriorly lower angle compared to the fossil. The coronoid of Coleonyx variegatus and C. brevis also differ from the fossil in having a dorsoventrally expanded anterolateral process (Kluge 1962). The lateral crest on the coronoid process is almost vertically oriented in the fossil, but in examined Plestiodon and Scincella the crest is more obliquely oriented. Furthermore, the anterolateral process is more anteriorly oriented in the fossil but more ventrally oriented in Plestiodon (see also fig. 4 in Nash 1970). Based on differences from other NA lizards, the fossil coronoid is referable to Anguimorpha. Xenosaurus, except for X. rackhami, differs from the fossil in having a foramen on the anterolateral process (Evans 2008; Bhullar 2011). Heloderma differs in having a dorsoventrally expanded anterolateral process and Anniella differs in having a shorter coronoid process (Evans 2008). On this basis the fossil was identified to Anguidae.mbricata

Compound bone

Description

TxVP 41229-27094 is a right compound bone missing much of the portion anterior to the articular surface (Fig. 29). The retroarticular process is broadened and medially oriented. The dorsal surface of the retroarticular process is slightly concave, and the ventral surface bears a distinct sub-triangular depression. There is a ventral angular articulation facet. The articular surface is broad and saddle shaped. There are two small foramina posterior to the articular surface.

Identification

The fossil shares with anguimorphs, geckos, and scincids a medially directed and broadened retroarticular process (Estes et al. 1988). Geckos differ from the fossil in having a distinct notch on the medial margin of the retroarticular process (Estes et al. 1988). Scincids differ in having a tubercle or flange on the medial margin of the retroarticular process (Estes et al. 1988); however, this feature was not obvious in all examined specimens, particularly for Scincella (Fig. 31). The fossil differs from examined scincids in having a distinct sub-triangular depression on the ventral surface of the retroarticular process. Based on differences from other NA lizards, the fossil is referable to Anguimorpha. Examined Anniella differ in having a more medially slanted retroarticular process and examined Xenosaurus and Heloderma have a more slender retroarticular process (Evans 2008). The fossil is referable to Anguidae. A distinct sub-triangular depression on the ventral surface of the retroarticular process was observed in gerrhonotines and diploglossines but was absent in examined Ophisaurus. We refrain from making a more refined identification pending examination of additional skeletal material of diploglossines.

Figure 31.

Non-Pleurodontan Compound bones. Compound bones in dorsal view– A. Anelytropsis papillosus UF 86708; B. Coleonyx varegatus TxVP M-13892; C. Scincella lateralis TxVP M-5531; D. Plestiodon gilberti TxVP M-8587; E. Xantusia riversiana TxVP M-8505; F. Xantusia virigatus TxVP M-12130; G. Lepidophyma lowei LACM 143367; H. Aploglossus plicatus TNHC 34481; I. Aspidoscelis sonorae TxVP M-15670; J. Bipes canaliculatus CAS 134753; K. Heloderma suspectum TxVP M-9001; L. Xenosaurus grandis TxVP M-8960; M. Diploglossus millepunctatus TxVP M-9010; N. Diploglossus bilobatus TNHC 31933; O. Anniella pulchra TxVP M-8678; P. Ophisaurus attenuatus TxVP M-8979; Q. Gerrhonotus infernalis TxVP M-13441; R. Barisia imbricata TNHC 76984. Scale bars = 1 mm.

Anguinae Gray, 1825

Ophisaurus Daudin, 1803

Referred specimens: See Table S3.

Premaxilla

Description

TxVP 41229-28734 is a premaxilla with nine tooth positions (Fig. 32). Teeth are unicuspid. The rostral surface is rounded, and the nasal process is strongly curved posteriorly. The nasal process is thin and slightly waisted at the base and has a short posterior keel. There are lateral maxillary facets but no dorsal ossifications on the alveolar plate. The palatal plate has short posterior projections. The incisive process is large, round, and bilobed. There are small foramina posterolateral to the base of the nasal process and there is a single midline anterior foramen.

Figure 32.

Fossil anguines. TxVP 41229-28734 Anterior view of premaxilla; TxVP 41229-28413 Dorsal and medial view of right maxilla; TxVP 41229-28737 Dorsal view of frontal; TxVP 41229-28153 Dorsal view of parietal; TxVP 41229-25597 Lateral view of prefrontal; TxVP 41229-28467 Dorsal view of postfrontal; TxVP 41229-25585 Posterior and lateral view of quadrate; TxVP 41229-28356 Dorsal and ventral view of pterygoid; TxVP 41229-25602 Dorsal view of pterygoid; TxVP 41229-28388 Medial view of dentary; TxVP 41229-28445 Lateral and medial view of coronoid; TxVP 41229-29001 Dorsal and medial view of compound bone. Scale bars = 1 mm.

Identification

The fossil premaxilla is assigned to Anguimorpha based on having a large, round, and bilobed incisive process (Evans 2008; Fig. 33). The incisive process is relatively smaller and less distinctly bilobed in pleurodontans, scincids (when present), and xantusiids (Evans 2008). The fossil shares with anguids and Xenosaurus nine tooth positions (Conrad et al. 2011; Bhullar 2011; Scarpetta 2018). The fossil differs from Xenosaurus in lacking a rugose rostral surface of the premaxilla (Bhullar 2011). The fossil shares with Anguinae and Diploglossinae a forked palatal process (Evans 2008; Conrad et al. 2011; Scarpetta 2018). The fossil differs from Diploglossinae and is assigned to Anguinae based on the absence of a dorsal ossification on the palatal plate posterior to the medial ethmoidal foramen (Scarpetta 2018).

Figure 33.

Non-Pleurodontan Premaxillae. Premaxillae in anterior, dorsal, and ventral views– A. Anelytropsis papillosus UF 86708; B. Coleonyx variegatus TxVP M-12109; C. Scincella lateralis TxVP M-4489; D. Plestiodon gilberti TxVP M-8587; E. Xantusia riversiana TxVP M-8505; F. Xantusia virigatus TxVP M-12130; G. Lepidophyma lowei LACM 143367; H. Aploglossus plicatus TNHC 34481; I. Aspidoscelis sonorae TxVP M-15670; J. Bipes canaliculatus CAS 134753; K. Heloderma suspectum TxVP M-9001; L. Diploglossus bilobatus TNHC 31933; M. Anniella pulchra TxVP M-8678; N. Ophisaurus ventralis TxVP M-8585; O. Gerrhonotus infernalis TxVP M-13441; P. Barisia imbricata TNHC 76984. Scale bars = 1 mm.

Maxilla

Description

TxVP 41229-28413 serves as the basis for our description and is a right maxilla (Fig. 32). There are 17 tooth positions and teeth are unicuspid with medial striations. The dorsal portion of the facial process is broken, but it is broad. The anterior face of the facial process gently curves medially and has an anterodorsal projection. The premaxillary process is strongly bifurcated with a longer, pointed lateral projection and a shorter medial lappet. The crista transversalis trends anteromedially from the facial process. There is a narrow palatal shelf with a rounded palatine process. The palatal shelf becomes especially narrow anterior to the palatine process. There is a deep recess on the medial surface of the facial process. The lateral wall of the posterior orbital process is short with a small notch posteriorly. The dorsal surface of the postorbital process has a shallow jugal groove. There is a large superior alveolar foramen on the palatal shelf medial to the palatine process, and five lateral nutrient foramina.

Identification

Fossil maxillae share with some scincids and anguimorphs unicuspid teeth with striated crowns (Estes 1963; Smith 2009b; Fig. 34). Fossils differ from examined scincids in lacking a large notch at the end of the posterior orbital process (see also fig. 5 in Čerňanský and Syromyatnikova 2021). Scincella differs in lacking striations on the crowns (Townsend et al. 1999). Examined Plestiodon differ in having the crista transversalis abruptly trend medially anterior to the facial process and having a much wider palatal shelf. Based on these differences, the fossils are referable to Anguimorpha.

Anniella and Heloderma differ from the fossils in having more pointed and recurved teeth as well as fewer tooth positions (up to seven in Anniella and up to ten in Heloderma; Torien 1950; Evans 2008). Xenosaurus differs in having fused osteoderms on the lateral surface of the facial process (Bhullar 2011). Fossils are assigned to Anguidae. Fossils share with anguines and diploglossines a deeply notched premaxillary process (Meszoely 1970). Fossil maxillae share with Anguinae sharp and widely spaced teeth (Meszoely 1970). Some species of Abronia (e.g., Abronia mixteca; Scarpetta et al. 2021) and perhaps some diploglossines (e.g., Diploglossus fasciatus; see fig. 2 in Syromyatnikova and Aranda 2022) also have sharp and widely spaced teeth, but in Abronia and diploglossines, the palatal shelf anterior to the palatine process does not narrow to the same degree as in fossils and examined anguines.

Figure 34.

Non-Pleurodontan Maxillae. Maxillae in medial and dorsal views– A. Anelytropsis papillosus UF 86708; B. Coleonyx variegatus TxVP M-12109; C. Scincella lateralis TxVP M-4489; D. Plestiodon gilberti TxVP M-8587; E. Xantusia riversiana TxVP M-8505; F. Xantusia virigatus TxVP M-12130; G. Lepidophyma lowei LACM 143367; H. Aploglossus plicatus TNHC 34481; I. Aspidoscelis sonorae TxVP M-15670; J. Bipes canaliculatus CAS 134753; K. Heloderma suspectum TxVP M-9001; L. Xenosaurus grandis TxVP M-8960; M. Anniella pulchra TxVP M-8678; N. Diploglossus bilobatus TNHC 31933; O. Ophisaurus ventralis TxVP M-8585; P. Gerrhonotus infernalis TxVP M-13441; Q. Gerrhonotus infernalis TxVP M-13440; R. Barisia imbricata TNHC 76984. Scale bars = 1 mm.

Frontal

Description

TxVP 41229-28737 is an unfused right frontal (Fig. 32). There are osteoderms with a pitted texture fused to the frontal much of its dorsal surface. The lateral frontal sulcus separates the larger frontal shield from the smaller posterolateral frontoparietal shield, and the medial frontal sulcus separates a minute interfrontal shield (sensu Klembara et al. 2017). Anterolaterally, there is a prefrontal facet, and anterodorsally, there is a nasal facet. The anterior end is elongated and pointed without a distinct anterolateral process. The medial margin and interorbital margins are straight, and the posterolateral processes gently curve laterally. The posterior margin is straight with a posterolateral parietal articulation facet. There is a postfrontal facet along the posterolateral edge. The anteroventral portion of the crista cranii is broken, but the crest is well-developed, tall, and anteroposteriorly long.

Identification

The fossil shares with some anguimorphs and most scincids co-ossified osteoderms (Estes et al. 1988), well-developed and ventrally directed cristae cranii (=subolfactory processes of McDowell and Bogert 1954), and an unfused frontal (Estes et al. 1988). The sculpting on the dorsal surface in scincids is more vermiculate compared to the fossil and to extant anguimorphs which have a pitted texture, such as Ophisaurus and Elgaria (Conrad 2008; Fig. 35). Plestiodon differ in having exceptionally slender cristae cranii (Nash 1970), and Scincella and Mabuya differ in having a fused frontal (Greer 1970). Examined Plestiodon also differs from the fossil and anguines, except for Anguis fragilis (Klembara et al. 2017), in having a broader and less pointed anterior portion of the unfused frontal. Frontals are assigned to Anguimorpha. Among NA anguimorphs, unfused frontals occur in Anguinae, Diploglossinae, Heloderma, and Anniella (Evans 2008). Heloderma and Anniella differ in having the cristae cranii curve to meet at the midline, forming an enclosed olfactory canal (Evans 2008). In the fossil and other anguines except for Anguis fragilis (Klembara et al. 2017), there is a pointed anterior portion of the unfused frontal. The anterior portion of the frontal is broader in diploglossines (Evans 2008). Frontals are assigned to Anguinae based on the presence of an unfused frontal and a pointed anterior portion of the frontal.

Figure 35.

Non-Pleurodontan Frontals. Frontals in dorsal and lateral views– A. Anelytropsis papillosus UF 86708; B. Coleonyx variegatus TxVP M-12109; C. Scincella lateralis TxVP M-4489; D. Plestiodon gilberti TxVP M-8587; E. Xantusia riversiana TxVP M-8505; F. Xantusia virigatus TxVP M-12130; G. Lepidophyma lowei LACM 143367; H. Aploglossus plicatus TNHC 34481; I. Aspidoscelis sonorae TxVP M-15670; J. Bipes canaliculatus CAS 134753; K. Heloderma suspectum TxVP M-8593; L. Xenosaurus grandis TxVP M-8960; M. Diploglossus bilobatus TNHC 31933; N. Diploglossus millepunctatus TxVP M-9010; O. Anniella pulchra TxVP M-8678; P. Ophisaurus ventralis TxVP M-8585; Q. Gerrhonotus infernalis TxVP M-13441; R. Barisia imbricata TNHC 76984. Scale bars = 1 mm.

Parietal

Description

TxVP 41229-28153 serves as the basis for our description and is a parietal missing only the ends of the postparietal processes (Fig. 32). The parietal table is rectangular and is covered dorsally in co-ossified osteoderms with a pitted texture. The interparietal sulcus separates the triangular interparietal shield from the lateral shields (sensu Klembara et al 2017). The interparietal shield reaches the posterior smooth region of the parietal table. The anterior edge is straight with small frontal tabs and interlacing articulation facets for the frontal. The posterior edge between the postparietal processes is characterized by two small depressions (nuchal fossae) separated by a small ridge. The postparietal processes are broad and flat at the bases. The ventrolateral crests are low, positioned along the lateral margins, and border the cerebral vault. There is a low ridge anterior to the pit for the processus ascendens. The ventrolateral crests curve medially onto the postparietal processes, and together with a ventrolateral ridge on the postparietal process, define distinct depressions. There is a large parietal foramen within the interparietal shield.

Identification

The fossil shares with some anguimorphs and scincids co-ossified osteoderms with dorsal sculpting (Estes et al. 1988), a parietal foramen enclosed by the parietal (Estes et al. 1988), and ventrally projecting parietal crests or processes (Estes et al. 1988; Evans 2008; Ledesma and Scarpetta 2018; Fig. 36). Scincids differ in having long posterior projections (median extensions of Evans 2008) on the posterior edge of the parietal table between the postparietal processes (Evans 2008; Gauthier et al. 2012; see also fig. 8 in Jerez et al. 2015). Scincids further differ from the fossil in having distinct ventrolateral crests that include long, thin, ventral projections (Nash 1970; Evans 2008) and the postparietal processes in examined scincids are more separated relative to the fossil. Parietals are assigned to Anguimorpha. Heloderma differs in lacking a parietal foramen (Estes et al. 1988) and Anniella differs in having the ventrally projecting parietal crests developed into extensive sheets of bone (Evans 2008). Xenosaurids differ in having heavily sculptured dorsal roofing bones with many bumpy, dome-like co-ossified osteoderms (Gauthier 1982; Bhullar 2010, 2011). Parietals are assigned to Anguidae.

Figure 39.

Non-Pleurodontan Quadrates. Quadrates in posterior and lateral views– A. Anelytropsis papillosus UF 86708; B. Coleonyx variegatus TxVP M-12109; C. Scincella lateralis TxVP M-4489; D. Plestiodon obsoletus TxVP M-8574; E. Xantusia riversiana TxVP M-8505; F. Xantusia virigatus TxVP M-12130; G. Lepidophyma lowei LACM 143367; H. Aploglossus plicatus TNHC 34481; I. Aspidoscelis sonorae TxVP M-15670; J. Bipes canaliculatus CAS 134753; K. Heloderma suspectum TxVP M-8593; L. Xenosaurus grandis TxVP M-8960; M. Diploglossus bilobatus TNHC 31933; N. Anniella pulchra TxVP M-8678; O. Ophisaurus ventralis TxVP M-8585; P. Gerrhonotus infernalis TxVP M-13441; Q. Barisia imbricata TNHC 76984. Scale bars = 1 mm.

Xenosaurus differs from the fossils in having a wider quadrate with a shallower lateral conch (Bhullar 2011). Anniella differs in having a thin quadrate in posterior view that is widened in medial and lateral views (Toerien 1950). Fossils were assigned to Anguidae. Examined gerrhonotines (see fig. 19 in Ledesma and Scarpetta 2021) and diploglossines (see also fig. 2 in Bochaton et al. 2016b) differ from the fossil and examined Ophisaurus in having a more laterally extensive pterygoid lamina and a more curved tympanic crest. Fossils are assigned to Anguinae.

Pterygoid

Description

TxVP 41229-28356 is a left pterygoid that is missing the distal end of the palatine process (Fig. 32). The palatine process is narrow with an anterior palatine facet. The transverse process is pointed and extends anterolaterally. The transverse process bears a ridge on the dorsal surface for insertion of the superficial pseudotemporal muscle and a developed ectopterygoid facet. There is a large ridge on the ventral surface for insertion of the pterygomandibular muscle, and on the dorsal surface there is a small, deep fossa columella. The epipterygoid crest is anteromedial to the fossa columella. There is a long postepipterygoid groove (sensu Good 1987) on the quadrate process. The quadrate process is elongated, and the medial surface has a shallow groove that serves for insertion of the pterygoideus muscle. There is a small notch in the quadrate process that is likely taphonomic. There is a small medial projection at the floor of the basipterygoid fossa and a broad patch of 19 pterygoid tooth positions with 13 pterygoid teeth present. TxVP 41229-25602 is missing the distal ends of the palatine and quadrate processes and does not differ from TxVP 41229-28356 substantively.

Identification

Fossils share with some anguimorphs and pleurodontans a medial projection at the floor of the basipterygoid fossa (Evans 2008; Smith 2009b). Examined NA pleurodontans, except Petrosaurus, differ in having the transverse process oriented more medially (Fig. 40). Examined Petrosaurus differ in lacking pterygoid teeth (Etheridge 1964) and lacking a long postepiterygoid groove on the quadrate process. Fossils are assigned to Anguimorpha.

Xenosaurus and Anniella lackpterygoid teeth (Evans 2008). Heloderma differs in having only a single row of pterygoid teeth located on an elevated ridge (Evans 2008). Thus, fossils are assigned to Anguidae. The presence and number of teeth are variable in gerrhonotines (Ledesma et al. 2021; Scarpetta et al. 2021) and Ophisaurus (Taylor 1940), but diploglossines lack pterygoid teeth (Rieppel 1980; Evans 2008). The epipterygoid crest in examined anguines is more distinct and projects farther medially compared to examined gerrhonotines (Klembara et al. 2017; Ledesma et al. 2021). The palatal process is narrower in examined Ophisaurus compared to gerrhonotines and the space between the transverse process and the palatal plate (suborbital incisure of Klembara et al. 2017) is wider in examined gerrhonotines and diploglossines compared to Ophisaurus, thus fossils are assigned to Anguinae.

Dentary

Description

TxVP 41229-28388 serves as the basis for our description and is a left dentary with 18 tooth positions and 14 teeth present (Fig. 32). Teeth are unicuspid, but the crowns are slightly eroded. There are three posterolateral processes, including a pointed coronoid process, a long surangular process, and a short angular process. Medially, a minute surangular spine is visible (sensu Klembara et al. 2014). The Meckelian canal is open ventrally. The intramandibular septum has a free posteroventral margin. The dental shelf is narrow, and there is a posteriorly projecting splenial spine (sensu Klembara et al. 2014). There are seven nutrient foramina arranged in a row on the lateral surface. TxVP 41229-27759 differs in lacking an intramandibular septum with a free posteroventral margin and having a long surangular spine.

Identification

Dentaries are assigned to Anguimorpha based on the presence of a discrete surangular process (Gauthier 1982; Good 1988) and a posteriorly projecting splenial spine (Conrad 2008; Čerňanský and Augé 2019; Fig. 41). Dentaries are assigned to Anguidae based on the presence of an intramandibular septum with a free posteroventral margin although this morphology is absent in some anguines (Klembara et al. 2014; Scarpetta 2018; Scarpetta et al. 2021) and is indeed absent in TxVP 41229-27759. Fossils differ from other NA anguimorphs except for Ophisaurus in having a surangular spine (Klembara et al. 2014). A surangular spine was reported in some diploglossines (Bochaton et al. 2016b; Syromyatnikova and Aranda 2022); however, this feature is likely a posterior extension on the intramandibular septum described in other anguids (Klembara et al. 2014; Ledesma and Scarpetta 2018). Furthermore, diploglossines differ from the fossils in lacking a splenial spine and having the anterior inferior alveolar foramen completely within the splenial (Syromyatnikova and Aranda 2022). Fossils are assigned to Anguinae.

Figure 40.

Non-Pleurodontan Pterygoids. Pterygoids in dorsal view– A. Anelytropsis papillosus UF 86708; B. Coleonyx variegatus TxVP M-12109; C. Scincella lateralis TxVP M-4489; D. Plestiodon gilberti TxVP M-8587; E. Xantusia riversiana TxVP M-8505; F. Xantusia virigatus TxVP M-12130; G. Lepidophyma lowei LACM 143367; H. Aploglossus plicatus TNHC 34481; I. Aspidoscelis sonorae TxVP M-15670; J. Bipes canaliculatus CAS 134753; K. Heloderma suspectum TxVP M-9001; L. Xenosaurus grandis TxVP M-8960; M. Diploglossus bilobatus TNHC 31933; N. Anniella pulchra TxVP M-8678; O. Ophisaurus attenuatus TxVP M-8979; P. Gerrhonotus infernalis TxVP M-13441; Q. Barisia imbricata TNHC 76984. Scale bars = 1 mm.

Figure 41.

Non-Pleurodontan Dentaries. Dentaries in medial view– A. Anelytropsis papillosus UF 86708; B. Coleonyx variegatus TxVP M-12109; C. Scincella lateralis TxVP M-4489; D. Plestiodon gilberti TxVP M-8587; E. Xantusia riversiana TxVP M-8505; F. Xantusia virigatus TxVP M-12130; G. Lepidophyma lowei LACM 143367; H. Aploglossus plicatus TNHC 34481; I. Aspidoscelis sonorae TxVP M-15670; J. Bipes canaliculatus CAS 134753; K. Heloderma suspectum TxVP M-9001; L. Xenosaurus grandis TxVP M-8960; M. Diploglossus bilobatus TNHC 31933; N. Anniella pulchra TxVP M-8678; O. Gerrhonotus infernalis TxVP M-13441; P. Ophisaurus attenuatus TxVP M-8979; Q. Ophisaurus ventralis TxVP M-8585; R. Barisia imbricata TNHC 76984. Scale bars = 1 mm.

Coronoid

Description

TxVP 41229-28445 is a left coronoid (Fig. 32). The coronoid process is short and rounded and the anteromedial process is elongated but is missing the distal tip. The posteromedial process is directed posteriorly and has a notch on the posterodorsal end. There is a short medial crest that extends from the coronoid process and diminishes on the posteromedial process. There is a large, anteriorly projecting lateral process. The anteromedial process has a medial splenial facet that, together with an anteriorly projecting lateral process, forms a narrow articulation facet for the coronoid process of the dentary. There is no lateral crest and the facet for the dorsal articulation with the surangular is narrow.

Identification

The fossil coronoid differs from xantusiids and some pleurodontans in having an anterolateral process (Estes et al. 1988). The fossil differs from examined NA pleurodontans with an anterolateral process (see discussion in Crotaphytidae section above) in having a more posteriorly oriented posteromedial process. The fossil differs from examined Aspidoscelis and Ameiva in lacking a deeply notched posterior edge forming dorsal and ventral rami (Tedesco et al. 1999; Fig. 30). Furthermore, Aspidoscelis, Ameiva, and Pholidoscelis differ in having a lateral crest running from the apex of the coronoid process anteroventrally onto the anterolateral process (Tedesco et al. 1999; Bochaton et al. 2019). The fossil shares with several gymnophthalmoids a low coronoid process and widely divergent anteromedial and posteromedial processes (Evans 2008; Roscito and Rodrigues 2010). The fossil differs from examined gymnophthalmoids with a low coronoid process in having a relatively broader posteromedial process (see figs. 7-9 in Roscito and Rodrigues 2010; fig. 2 in Holovacs et al. 2020). Examined Coleonyx variegatus, C. brevis, Sphaerodactylus roosevelti, and Thecadactylus rapicauda differ from the fossil in having a thinner posteromedial process (Kluge 1962; Daza et al. 2008; Bochaton et al. 2018). The posteromedial process is slightly wider in C. elegans and C. mitratus compared to other species (Kluge 1962) but examined Coleonyx including C. elegans differ in having a pronounced lateral crest on the coronoid process (see also fig. 7 in Kluge 1962). The lateral crest on the coronoid process is absent in the fossil, but in examined Plestiodon and Scincella, the crest is pronounced and obliquely oriented. Furthermore, the anterolateral process is more anteriorly oriented in the fossil but more ventrally oriented in Plestiodon (see also fig. 4 in Nash 1970). Based on differences from other NA lizards, the fossil coronoid is referable to Anguimorpha. Xenosaurus, except for X. rackhami, differs from the fossil in having a foramen on the anterolateral process (Evans 2008; Bhullar 2011). Heloderma differs in having a dorsoventrally expanded anteromedial process (Evans 2008). Anniella differs in having a facet for the coronoid process of the dentary extending on the anterior face of the coronoid process (Evans 2008). The fossil is assigned to Anguidae. The coronoid process of examined gerrhonotines and diploglossines is generally taller and more distinct than that of the fossil and of some Ophisaurus. On that basis, the fossil was identified to Anguinae.

Compound bone

Description

TxVP 41229-29001 is a left compound bone missing the anterior portion of the prearticular and posterior tip of the retroarticular process (Fig. 32). The adductor fossa is narrow. The retroarticular process is broadened and medially oriented. The dorsal surface of the retroarticular process is depressed. The surangular is short and the dorsal margin is rounded. There is a distinct squared-off tubercle anterior to the articular surface. There is a ventral angular articulation facet and an anterolateral coronoid facet. There is a foramen on the surangular just posterior to the adductor fossa. On the lateral surface there are two anterior surangular foramina and one posterior surangular foramen. There is also a dorsal foramen just anterior to the medial process.

Identification

The fossil compound bone shares with anguimorphs, geckos, and scincids a medially directed and broadened retroarticular process (Estes et al. 1988). Geckos differ from the fossil in having a distinct notch on the medial margin of the retroarticular process (Estes et al. 1988). Scincids differ in having a tubercle or flange on the medial margin of the retroarticular process (Estes et al. 1988), but this feature was not obvious in all examined specimens, particularly in Scincella. Examined scincids differ in having a narrower and taller tubercle anterior to the articular surface and in having an adductor fossa that extends farther posteriorly. Examined Scincella differ in having a comparatively elongated and more rectangular retroarticular process. Based on differences from other NA lizards, the fossil is referable to Anguimorpha.

Among anguimorphs, Xenosaurus differs in having a deep subcoronoid fossa (Bhullar 2011). Examined Anniella differ in having a more retroarticular process that slants medially, and Heloderma have a more slender retroarticular process (Evans 2008). The fossil is referable to Anguidae. Among anguids, the fossil differs from many examined gerrhonotines and diploglossines in having a very short adductor fossa with a distinctly separate posteromedial surangular foramen. Some examined gerrhonotines also have a short adductor fossa with a distinctly separate posteromedial surangular foramen but differ in having a more mediolaterally expanded retroarticular process. On this basis, the fossil is referred to Anguinae.

Gerrhonotinae Tihen, 1949

Referred specimens: See Table S3.

Dentary

Description

TxVP 41229-27659 is a right dentary with 26 tooth positions (Fig. 29). Teeth bear medial striations. Mesial teeth are unicuspid, pointed, and slightly recurved while distal teeth are near-bicuspid and more squared-off. The coronoid process is well-developed and pointed, and the angular process is present but broken posteriorly. There is no surangular process. The Meckelian canal is open ventrally. The intramandibular septum has a free posteroventral margin. The dental shelf is broad and is slanted ventromedially. There is a posteriorly projecting splenial spine. There are six nutrient foramina arranged in a row on the lateral surface.

Identification

The fossil is assigned to Anguimorpha based on the presence of a posteriorly projecting splenial spine (Conrad 2008; Čerňanský and Augé 2019). Dentaries are assigned to Anguidae based on the presence of an intramandibular septum with a free posteroventral margin (Gauthier 1982; Klembara et al. 2014; Scarpetta 2018; Scarpetta et al. 2021). Diploglossines differ from the fossils in lacking a splenial spine and in having the anterior inferior alveolar foramen contained within the splenial (Syromyatnikova and Aranda 2022). Ophisaurus differs from the fossil in having a long surangular process and having a surangular spine (Klembara et al. 2014; Scarpetta et al. 2021). The fossil is assigned to Gerrhonotinae.

Clade composed of (Gerrhonotus, (Barisia, Abronia))

Referred specimens: See Table S3.

Premaxilla

Description

TxVP 41229-27657 is a premaxilla with ten tooth positions (Fig. 29). Teeth are unicuspid. The anterior rostral surface is rounded, and the nasal process is curved posteriorly and broken at the posterior end. The nasal process is wide and has lateral notches near the base. The nasal process tapers posteriorly and has a well-developed posterior keel. On the alveolar plate, there are lateral maxillary facets and dorsal ossifications that form an ossified bridge with the nasal process. Posteriorly, the palatal plate is slightly broken and has a wavy posterior edge. The incisive process is large, round, and slightly bilobed. There are large foramina posterolateral to the base of the nasal process and an anterior foramen between the ossified bridge, the nasal process, and the alveolar plate on either side.

Identification

The fossil premaxilla is assigned to anguimorpha based on having a large, round, and bilobed incisive process (Evans 2008). The incisive process is comparatively smaller and less distinctly bilobed in pleurodontans, scincids (when present), and xantusiids (Evans 2008). Among NA anguimorphs, the fossil shares with anguids and Xenosaurus nine or greater tooth positions (Conrad et al. 2011; Bhullar 2011; Scarpetta 2018). The fossil differs from Xenosaurus in lacking a rugose rostral surface of the premaxilla (Bhullar 2011). Anguinae and Diploglossinae differ from the fossil in having a forked palatal process (Evans 2008; Conrad et al. 2011; Scarpetta 2018). The fossil is assigned to Gerrhonotinae.

The fossil is identifiable to the clade (Desertum, (Gerrhonotus, (Barisia, Abronia))) based on the presence of an ossified bridge between the nasal process and the body of the premaxilla (Scarpetta et al. 2021). An ossified bridge also occurs in some species of Elgaria, but the bridge is much thinner (Ledesma et al. 2021). Furthermore, most Elgaria have a midline anterior foramen, which is absent on the fossil (Scarpetta et al. 2021). Examined Desertum lugoi differ in having a thinner nasal process that sometimes narrows towards the base (Ledesma et al. 2021). On that basis, the fossil is assigned to the clade (Gerrhonotus, (Barisia, Abronia)).

Jugal

Description

TxVP 41229-26858 is a right jugal that is missing much of the suborbital process (Fig. 29). There is a distinct ventral maxillary facet on the suborbital process. The quadratojugal process (jugal spur) is long and pointed. The postorbital process is long and is directed dorsally and has a postorbital facet on the anteromedial surface. On the medial surface, there is a medial ridge that is located at the midline of the suborbital and postorbital processes. The medial ridge defines the anterior border of a small depression on the medial surface anterior to the quadratojugal process. There are two medial and four lateral foramina near the inflection point.

Identification

TxVP 41229-26858 is assigned to Anguimorpha based on the presence of a medial ridge located at the midline of the suborbital and postorbital processes (Čerňanský et al. 2014). The fossil differs from NA pleurodontans in having a quadratojugal process and a dorsally directed postorbital process (Gauthier et al. 1988; Smith 2009a; Fig. 42). Geckos have a highly reduced jugal, and dibamids lack a jugal (Greer 1985; Evans 2008). Examined scincids differ in having a long and thin suborbital process with a distinct notch on the ventral margin and a large depression (coronoid recess of Smith 2011) on the medial surface near the inflection point. Teiioids differ in having a distinct medial ectopterygoid process, which is also present, albeit smaller, in some gymnophthalmoids (Evans 2008). Xantusiids differ in having a short suborbital process, and Xantusia riversiana and Lepidophyma have an anteroposteriorly widened postorbital process (Savage 1963).

Figure 42.

Non-Pleurodontan Jugals. Jugals in lateral view– A. Coleonyx elegans UF 11258; B. Scincella lateralis TxVP M-4489; C. Plestiodon gilberti TxVP M-8587; D. Xantusia riversiana TxVP M-8505; E. Xantusia virigatus TxVP M-12130; F. Lepidophyma lowei LACM 143367; G. Aploglossus plicatus TNHC 34481; H. Aspidoscelis sonorae TxVP M-15670; I. Heloderma suspectum TxVP M-8593; J. Xenosaurus grandis TxVP M-8960; K. Diploglossus bilobatus TNHC 31933; L. Panolopus costatus UF 59382; M. Anniella pulchra FMNH 130479; N. Ophisaurus ventralis TxVP M-8585; O. Gerrhonotus infernalis TxVP M-13441; P. Barisia imbricata TNHC 76984. Scale bars = 1 mm.

Among NA anguimorphs, Anniella differs in having a reduced jugal (Toerien 1950) and Heloderma differs in that the anterior and posterior processes form a right angle (Evans 2008). Xenosaurus has co-ossified osteoderms or sculpturing on the lateral surface of the jugal (Bhullar 2011). The fossil was assigned to Anguidae. A quadratojugal process is usually present in anguids (Evans 2008; Klembara et al. 2017; Scarpetta 2021). The length of the quadratojugal process in the fossil is longer than that of examined Ophisaurus but is similar to that present in some species of Gerrhonotus, Barisia, and Abronia (Klembara et al. 2017; Ledesma et al. 2021; Scarpetta et al. 2021). An examined Celestus enneagrammus (FMHN 108860) and Panolopus costatus (UF 59382) also have a long quadratojugal process but differ from the fossil in having a relatively shorter orbital process. Examined Desertum lugoi have a relatively shorter quadratojugal process. Jugals are assigned to the clade (Gerrhonotus, (Barisia, Abronia)) on this basis. Barisia differs in having sculpturing on the lateral surface of the jugal (Scarpetta et al. 2021) so the fossil likely represents either Gerrhonotus or Abronia.

Gerrhonotus Wiegmann, 1828

Referred specimens: See Table S3.

Maxilla

Description

TxVP 41229-27438 is a right maxilla (Fig. 29). There are 22 tooth positions. The teeth are unicuspid with medial striations on the crowns, and most are recurved. The lateral surface of the maxilla is highly sculptured. The facial process is tall and broad, and gently curves dorsomedially. The medial margin of the facial process has a distinct nasal facet, and the posterior margin has a large notch. The premaxillary process is long and bifurcated with a longer lateral projection and a shorter medial lappet. The crista transversalis is low and trends anteromedially from the facial process, defining the medial border of a shallow depression on the premaxillary process. There is a narrow palatal shelf without a distinctly projecting palatine process. There is a deep, elongate medial recess on the medial surface of the facial process. The lateral wall of the posterior orbital process is short. The dorsal surface of the postorbital process has an elongate, deep jugal groove and a small ectopterygoid facet at the posterior end. There is an opening for the superior alveolar canal anterior to the facial process. There are three large superior alveolar foramina (maxillary trigeminal foramina of Evans 2008) on the palatal shelf medial to the palatine process and eight lateral nutrient foramina.

Identification

Fossil maxillae share with some scincids and anguimorphs unicuspid teeth with striated crowns (Estes 1963; Smith 2009b). Fossils differ from examined scincids in lacking a large notch at the end of the posterior orbital process (see also fig. 5 in Čerňanský and Syromyatnikova 2021). Furthermore, Scincella differs in lacking striations on the crowns (Townsend et al. 1999) and examined Plestiodon differ in that the crista transversalis abruptly trends medially anterior to the facial process and the palatal shelf is wider. Based on these differences, the fossils are referable to Anguimorpha.

Anniella and Heloderma differ from the fossils in having a greater number of pointed and recurved teeth as well as fewer tooth positions (up to seven in Anniella and up to ten in Heloderma; Torien 1950; Evans 2008). Xenosaurus differs in having fused osteoderms laterally on the facial process (Bhullar 2011). Fossils are assigned to Anguidae. The fossil is assigned to Gerrhonotinae and differs from anguines and diploglossines in having an elongated premaxillary process that lacks a deep anterior notch (Meszoely 1970). Some gerrhonotines have a notch where the lacrimal articulates with the posterior edge of the facial process; however, a large notch as seen on the fossil only occurs only in Gerrhonotus infernalis among examined gerrhonotines (Ledesma et al. 2021) and is absent in other examined anguids.

Scincidae Gray, 1825

Referred specimens: See Table S3.

Compound bone

Description

TxVP 41229-26992 is a right compound bone missing only the anterior portion of the prearticular (Fig. 43). The adductor fossa is anteroposteriorly long. The retroarticular process is narrow and elongated posteriorly. There is a medial ridge that extends from the posterior margin of the articular surface to the medial edge of the retroarticular process, which bears a small medial tubercle. The dorsal and ventral surfaces of the retroarticular process are characterized by slight depressions. There is a tall, rounded tubercle anterior to the articular surface. The anterodorsal margin of the surangular has a dorsally expanded crest for articulation with the coronoid. There is a ventral angular articulation facet and a “v” shaped facet on the anterolateral surface of the surangular for articulation with the dentary. There are both anterior and posterior surangular foramina. There is also a dorsal foramen just anterior to the dorsal tubercle and a foramen posterior to the articular surface. TxVP 41229-26998 does not differ substantially.

Figure 43.

Fossil scincids. TxVP 41229-26870 Dorsal view of frontal; TxVP 41229-27663 Medial and dorsal view of right maxilla; TxVP 41229-26008 Dorsal of frontal; TxVP 41229-27317 Dorsal view of parietal; TxVP 41229-27716 Lateral view of left prefrontal; TxVP 41229-29162 Lateral view of right prefrontal; TxVP 41229-27750 Lateral and medial view of left jugal; TxVP 41229-25904 Dorsal, posterior, and lateral view of left quadrate; TxVP 41229-28867 Posterior view of right quadrate; TxVP 41229-27181 Dorsal view of left pterygoid; TxVP 41229-28300 Dorsal view of right pterygoid; TxVP 41229-27353 Medial view of right dentary; TxVP 41229-28062 Lateral and medial view of right coronoid; TxVP 41229-26998 Dorsal view of right compound bone; TxVP 41229-28649 Dorsal view of left compound bone; TxVP 41229-28060 Dorsal view of right compound bone; TxVP 41229-26992 Dorsal view of left compound bone. Scale bars = 1 mm.

Identification

Fossils share with scincids, anguimorphs, and geckos a medially directed retroarticular process (Estes et al. 1988). Fossils differ from geckos in lacking a notch on the medial margin of the retroarticular process (Estes et al. 1988). Fossils differ from anguimorphs and geckos in having a medial tubercle on the retroarticular process, although a small tubercle was found in a few anguimorph taxa (e.g., Diploglossus millepunctatus TxVP M-9010). Fossils differ from anguimorphs in having a “v” shaped facet on the anterolateral surface of the surangular (see also fig. 10E of Estes et al. 1988) which is present on all examined skinks except specimens of Plestiodon gilberti. Fossils also differ from anguimorphs in having a narrower and more rounded to pointed tubercle anterior to the articular surface. Examined anguimorphs tend to have a shorter and more squared-off tubercle. Fossils were assigned to Scincidae on this basis. Fossils share with examined Scincella, mabuyids (Čerňanský and Syromyatnikova 2021), and Plestiodon tetragrammus a relatively narrow retroarticular process. We refrain from making a more refined identification pending examination of additional skeletal material.

Sphenomorphinae Welch, 1982

Scincella Mittleman, 1950

Referred specimens: See Table S3.

Frontal

Description

TxVP 41229-26870 is a frontal (Fig. 43). Sculpturing is restricted to the posterodorsal surface of the bone. There are anterolateral facets for the prefrontal, and the anterior face of the frontal is defined by two short dorsal nasal facets formed by two anterolateral processes and an anteromedial process. The interorbital margins are waisted, and the posterolateral processes extend laterally. The posterior edge is slightly wavy and has interlacing articulation facets for the parietal. There are small postfrontal facets laterally on the posterolateral processes. The cristae cranii are low and diverge posteriorly along the lateral margins of the ventral surface. There is a broad ridge on the ventral surface near the interorbital margin creating separate anterior and posterior depressions.

Identification

Identification

Fossils share a medially directed and broadened retroarticular process with scincids, anguimorphs, and geckos (Estes et al. 1988). Fossils differ from geckos in lacking a notch on the medial margin of the retroarticular process (Estes et al. 1988). Fossils, except for TxVP 41229-28053, differ from anguimorphs and geckos in having a medial tubercle on the retroarticular process, although a small tubercle was found in a few anguimorph taxa as well (e.g., Diploglossus millepunctatus TxVP M-9010). Fossils differ from anguimorphs in having a narrower tubercle anterior to the articular surface. Examined anguimorphs tend to have a shorter and more squared-off tubercle. In examined Scincella and mabuyines, (Čerňanský and Syromyatnikova 2021) the retroarticular process is more narrow compared with the fossils. The retroarticular process is also narrow in examined Plestiodon tetragrammus. Fossils were assigned to Scincinae. Based on the shape of the retroarticular process (and given the good possibility that the fossils represent Plestiodon), the compound bones likely represent a species other than Plestiodon tetragrammus.

Teiidae Gray, 1827

Referred specimens: See Table S3.

Premaxilla

Description

TxVP 41229-27594 is a premaxilla with eight tooth positions (Fig. 44). Teeth are unicuspid. The rostral surface of the premaxilla is rounded. The nasal process is slightly broken posterolaterally, but it is evident that it is strongly curved posteriorly and tapers to a point. The process is slightly widened near the midpoint, and ventrally, there is a low keel. On the alveolar plate, there are lateral maxillary facets with small lateral notches. Posteriorly, the palatal plate is strongly incised and “v” shaped. There is no incisive process. There are two bilateral ethmoidal foramina posterior to the base of the nasal process, but no anterior foramen.

Description

TxVP 41229-27534 is a left postorbitofrontal missing the distal end of the anteromedial process (Fig. 44). The bone is slender and quadraradiate. The anteromedial process is slightly longer than the posteromedial processes. Between the medial processes, there is a facet for articulation with the frontal and parietal. The lateral margin is curved, and the posterolateral process is longer than the anterolateral process. The anterolateral process has a lateral facet for the jugal, and the posterolateral process has a lateral facet for articulation with the squamosal. There is a small ventral foramen on the central shaft of the bone.

Identification

The postfrontal and postorbital are fused into a single postorbitofrontal in some teiioids, xantusiids, some Xenosaurus, and some anguids (Estes et al. 1988; Evans 2008; Fig. 45). The fossil is quadraradiate as in some teiids and some Xenosaurus. The postorbitofrontal of Xenosaurus differs in having dorsal sculpturing and being much broader. The postfrontal and postorbital are separate in many gymnophthalmoids (Evans 2008). The postorbitofrontal is triradiate in examined gymnophthalmoids in which the postfrontal and postorbital are fused (Morales et al. 2019). The fossil is assigned to Teiidae.

Identification

The fossil shares with teiioids the presence of a distinct angular process and a widely opened adductor fossa (Estes et al. 1988). Examined gymnophthalmoids, except Calyptommatus (Guerra and Montero 2009) and Bachia (Tarazona et al. 2008), differ in having a wider and more rounded retroarticular process (Bell et al. 2003; Evans 2008; Roscito and Rodrigues 2010; Morales et al. 2019). Calyptommatus and Bachia differ in having a smaller angular process (Guerra and Montero 2009; Tarazona et al. 2008). Fossils are assigned to Teiidae.

Results

Our fossil identifications from Hall’s Cave resulted in a minimum of 11 lizard taxa, including five lizard taxa previously unknown from Hall’s Cave (Table 1). In most cases, we could not replicate the taxonomic level of previous fossil identifications. Our apomorphic framework permitted less taxonomically specific identifications most of the time. We recovered 17 separate lizard skull bones represented as fossils from Hall’s Cave. For most skeletal elements, identification could only be made to the family level; however, some elements (e.g., the premaxilla, maxilla, dentary, and jugal) permitted identification to the subfamily or genus level. Many of the skeletal elements that we recovered as fossils were relatively more robust skull bones (e.g., the frontal, parietal, dentary, maxilla, and compound bone), though we also recovered some smaller and more fragile elements (e.g., premaxilla, postfrontal, postorbital, jugal, and squamosal). Phrynosomatidae is the family with the most identified distinct taxa. This diversity in the fossil assemblage is recapitulated in the modern-day diversity with phrynosomatids being the most taxonomically diverse lizard family in the region. Most of the identified fossil lizard taxa inhabit the area around Hall’s Cave today, except for lizards within the Phrynosoma douglasii species complex (Table 2). Anguines (specifically Ophisaurus attenuatus) are reported to occur in Kerr County today; however, an examination of records of Ophisaurus attenuatus revealed only a single specimen (USNM 32826) in the county collected from three miles north of Kerrville in 1897. The next closest records of Ophisaurus are over 100 km east in Blanco and Hayes counties. There were a few extant lizard taxa that had records within 100 km of Hall’s Cave that we did not detect as fossils, including Coleonyx brevis, Anolis carolinensis, and Phrynosoma modestum. Possible Phrynosoma modestum fossils were previously reported from Hall’s Cave (Toomey 1993), yet, when we reexamined these fossils we found evidence arguing against assignment to Phrynosoma modestum (see Systematic Paleontology above).

View this table:

Table 2. Identified fossil lizard taxa represented in Hall’s Cave from this study compared to native extant species within 100 km of Hall’s Cave.

Discussion

An apomorphy-based fossil identification framework provides a replicable basis for employing the fossil record to understand the past. Such a solid foundation for fossil identifications is paramount for conducting larger evolutionary and ecological analyses using those data. Our study provides apomorphy-based identifications of fossil lizards from Hall’s Cave, and we add five new lizard taxa to the known diversity of the cave fauna. This work increases understanding of the past herpetofaunal diversity on the Edwards Plateau and sets the stage for further analyses examining past responses to environmental change. Additionally, since much of the previous work on Hall’s Cave focused on mammals (Toomey 1993) and plants (Cordova and Johnson 2019), our work on the fossil lizards adds a new dimension towards examining dynamics of the larger ecosystem in the region through time.

Many of our apomorphic identifications are at higher taxonomic levels (i.e., at the family or genus level) compared to previous efforts to identify fossil lizards from this locality, most of which yielded species-level identifications (Parmley 1988; Toomey 1993). Fossil identifications at the genus or family level were also achieved from other Pleistocene sites when using an apomorphic identification framework (Bell et al. 2004). Higher-level fossil identifications make taxon-based paleoecological reconstructions less precise (Bell et al. 2004). Nevertheless, it is important to recognize the limitations of our data and acknowledge that morphology is not always able to provide robust species-level fossil identifications without making assumptions about changes in geographic distributions. Identifying and accepting the limitations of our data will lead to more robust and well-supported evolutionary and paleoecological reconstructions. Identification of fossils using apomorphies generally results in identifications at higher taxonomic levels relative to identifications made from a phenetic framework or based on comparative samples restricted by modern distributions. However, alternative or supplemental methods can be used to refine fossil identifications further. For example, quantitative morphological methods like geometric morphometrics have become more commonly applied towards identification of fossil remains (Gray et al. 2017). In some cases, fossil identifications may be hindered due to substantial intraspecific morphological variation that overwhelms any interspecific signal. Furthermore, fossils are often disarticulated and broken skeletal elements, which hampers their identification. Paleogenomic and paleoproteomic methods are useful for identifying fossils, broken and intact, from more recent geological times, and often can provide species-level identification of fossil remains (Kehlmaier et al. 2017; Harvey et al. 2019). However, preservation of organic molecules differs between geographic regions and time periods, and paleogenomic data are not always recoverable from fossil specimens (Reed et al. 2003). Despite its limitations, morphology-based identification methods are applicable across the vastness of geologic time and continue to be an important approach for interpreting fossil remains.

Although higher-level fossil identifications using apomorphies can make paleoecological and paleoenvironmental interpretation less precise, it is still possible to glean insights from these identifications (e.g., Mead et al. 2008; Ramm et al. 2021; Scarpetta 2021). For example, here we used apomorphies to provide additional support for the presence of an extirpated clade of short-horned lizards (Phrynosoma douglasii species complex) on the Edwards Plateau during the late Pleistocene to the early Holocene. The closest living species in the Phrynosoma douglasii species complex to Hall’s Cave, P. hernandesi, is found 435 km west in Jefferson County, Texas. However, there is a closer preserved specimen of P. hernandesi (MCZ R-8216) 285 km northwest in Mitchell County, Texas, collected in 1997. Toomey (1993) postulated that the extirpation of lizards in the P. douglasii species complex near Hall’s Cave may have been driven by complex ecological interactions, including climatic changes and potential changes in resource availability. Additional study, perhaps using stable isotope data, will shed more light on the cause of this extirpation.

There are a few extant lizard taxa (e.g., Coleonyx brevis, Anolis carolinensis) that live within 100 km of Hall’s Cave today that we did not detect as fossils. The absence of these taxa from Hall’s Cave may represent a true absence of these taxa from the area around Hall’s Cave. Alternatively, preservation or accumulation biases, particularly against the small and delicate bones of smaller taxa, like Coleonyx brevis, may also explain these absences. Although we found evidence contradicting the previous identifications of some fossils to Phrynosoma modestum, examination of additional material may confirm this taxon in the Hall’s Cave sequence. The absence of Anolis from the Hall’s Cave sequence is interesting because some skull elements of Anolis (e.g., dentary, parietal, frontal, maxilla) are relatively robust, easily recognizable, and commonly preserved as fossils in other Quaternary deposits (Auffenberg 1956). Although Anolis carolinensis is widespread in Texas today, including the areas around Hall’s Cave, there is a striking lack of Pleistocene fossil anoles in Texas (Holman 1969, 1995). Fossil Anolis are known from at least the late Oligocene of Florida (Chovanec 2014) and Anolis carolinensis was estimated to have experienced range expansion out of Florida during the Pleistocene (Campbell-Staton et al. 2012). An eastward expansion of the species range from Florida was estimated to have started around 300,000 years ago (Tollis and Boissinot 2014). A lack of fossil Anolis from the Pleistocene of Texas may indicate that they did not reach Texas until more recently; however, increased sampling of fossil sites, especially in east Texas, is needed to understand the dispersal pattern. Although our study represents only a single locality, it preserves evidence that for at least some lizard taxa, stability was not the rule during parts of the Quaternary. Additional study in other fossil localities across NA is necessary to form a more complete synthesis of herpetofaunal dynamics during the Quaternary.

A main goal of this work is to facilitate the identification of North American lizard fossils in a phylogenetically explicit context. Our hope is that researchers familiar with the lizard skeletal system will find our synthesis of previously reported and new apomorphies useful for identifying fossil lizard remains and will spur new investigation into patterns of morphological variation within the lizard skeletal system. Our figures are intended to showcase cranial osteological variation in North American lizards with diverse specimen and taxon sampling. Although we obtained a broad comparative sample, we were unable to obtain comparative specimens for all North American lizard families, genera, and species, especially those for which CT or dry-skeletal material is scarce or non-existent. Broadly, there is a paucity of information in the published literature on morphological variation in many vertebrate clades, including lizards (Evans 2008). An incomplete understanding of patterns of variation hinders our ability to make well-substantiated claims using the fossil record. Modern comparative morphological data provide a basis by which to interpret the fossil record (Bell et al. 2010), particularly for fossils from the more recent past (i.e., the Quaternary). Continued investigations into patterns of morphological variation in modern taxa are necessary for understanding patterns encountered in the fossil record (Bell et al. 2010), including interspecific variation and intraspecific variation (e.g., sexual dimorphism, ontogenetic variation, etc.).

Many of the fossils examined here were found in vials of fossils labeled “scrap bone.” These “scrap” fossils were often elements other than the commonly described upper and lower tooth bearing elements that are commonly described in the Quaternary paleoherpetological literature (Bell et al. 2010). It is important that these additional elements are recognized because, as we have shown here, there are apomorphies on various skeletal elements that are as useful or more useful for fossil identification (Smith 2009a, 2011). Increased recognition of lizard remains can lead to novel insights and discoveries related to NA lizards as well as a more holistic view of ancient faunal assemblages. We therefore specifically worked to include images of mainly disarticulated skeletal elements, as would likely be encountered in the fossil record, from a diverse set of NA lizards. This will be especially useful for researchers who do not specialize on lizards, and it is our hope that the images we provide here lead to an increased recognition and identification of lizard remains in fossil deposits.

Literature Cited

↵
Auffenberg W. 1956. ADDITIONAL RECORDS OF PLEISTOCENE LIZARDS FROM FLORIDA. Quarterly Journal of the Florida Academy of Sciences 19: 157–167.
OpenUrl
↵
1. Wright HE,
2. Frey DG
Auffenberg W, Milstead WW. 1965. REPTILES IN THE QUATERNARY OF NORTH AMERICA. In: Wright HE, Frey DG, eds. The Quaternary of the U.S. Princeton University Press, 557–568.
↵
Bell CJ. 1993. Fossil lizards from the Elsinore fault zone, Riverside County, California PaleoBios 15: 18–26.
OpenUrl
↵
Bell C, Evans S, Maisano J. 2003. The skull of the gymnophthalmid lizard Neusticurus ecpleopus (Reptilia: Squamata). Zoological Journal of the Linnean Society 139: 283–304.
OpenUrl
↵
Bell CJ, Gauthier JA, Bever GS. 2010. Covert biases, circularity, and apomorphies: A critical look at the North American Quaternary Herpetofaunal Stability Hypothesis. Quaternary International 217: 30–36.
OpenUrl CrossRef GeoRef Web of Science
↵
1. Barnosky AD
Bell CJ, Head JJ, Mead JI. 2004. Synopsis of the herpetofauna from Porcupine Cave. In: Barnosky AD, ed. Biodiversity Response to Climate Change in the Middle Pleistocene: the Porcupine Cave Fauna from Colorado. Berkeley, California: University of California Press, 117–126.
↵
Bhullar BAS. 2010. Cranial osteology of Exostinus serratus (Squamata: Anguimorpha), fossil sister taxon to the enigmatic clade Xenosaurus. Zoological Journal of the Linnean Society 159: 921–953.
OpenUrl
↵
Bhullar BAS. 2011. The Power and Utility Of Morphological Characters In Systematics: A Fully Resolved Phylogeny of Xenosaurus and Its Fossil Relatives (Squamata: Anguimorpha). Bulletin of the Museum of Comparative Zoology 160: 65–181.
OpenUrl
↵
Bochaton C, Boistel R, Casagrande F, Grouard S, Bailon S. 2016a. A fossil Diploglossus (Squamata, Anguidae) lizard from Basse-Terre and Grande-Terre Islands (Guadeloupe, French West Indies). Scientific Reports 6: 28475.
OpenUrl
↵
Bochaton C, Boistel R, Grouard S, Ineich I, Tresset A, Bailon S. 2019. Evolution, diversity and interactions with past human populations of recently extinct Pholidoscelis lizards (Squamata: Teiidae) from the Guadeloupe Islands (French West-Indies). Historical Biology 31: 140–156.
OpenUrl
↵
Bochaton C, Charles L, Lenoble A. 2021. Historical and fossil evidence of an extinct endemic species of Leiocephalus (Squamata: Leiocephalidae) from the Guadeloupe Islands. Zootaxa 4927: 383–409.
OpenUrl
↵
Bochaton C, Daza JD, Lenoble A. 2018. Identifying Gecko Species from Lesser Antillean Paleontological Assemblages: Intraspecific Osteological Variation within and Interspecific Osteological Differences between Thecadactylus rapicauda (Houttuyn, 1782) (Phyllodactylidae) and Hemidactylus mabouia (Moreau de Jonnès, 1818) (Gekkonidae). Journal of Herpetology 52: 313–320.
OpenUrl
↵
Bochaton C, Grouard S, Breuil M, Ineich I, Tresset A, Bailon S. 2016b. Osteological Differentiation of the Iguana Laurenti, 1768 (Squamata: Iguanidae) Species: Iguana iguana (Linnaeus, 1758) and Iguana delicatissima Laurenti, 1768, with some Comments on their Hybrids. Journal of Herpetology 50: 295–305.
OpenUrl
↵
1. Mead JI,
2. Meltzer DJ
Brewer. 1985. Herpetofaunas in the late Pleistocene: Extinctions and extralimital forms. In: Mead JI, Meltzer DJ, eds. Environments and extinctions: Man in late glacial North America. Orono, MA: Center for the Study of Early Man, 31–52.
↵
Burbrink FT, Grazziotin FG, Pyron RA, Cundall D, Donnellan S, Irish F, Keogh JS, Kraus F, Murphy RW, Noonan B, Raxworthy CJ, Ruane S, Lemmon AR, Lemmon EM, Zaher H. 2020. Interrogating Genomic-Scale Data for Squamata (Lizards, Snakes, and Amphisbaenians) Shows no Support for Key Traditional Morphological Relationships. Systematic Biology 69: 502–520.
OpenUrl
↵
Campbell-Staton SC, Goodman RM, Backström N, Edwards SV, Losos JB, Kolbe JJ. 2012. Out of Florida: mtDNA reveals patterns of migration and Pleistocene range expansion of the Green Anole lizard (Anolis carolinensis). Ecology and Evolution 2: 2274–2284.
OpenUrl
↵
Čerňanský A, Smith KT, Klembara J. 2014. Variation in the Position of the Jugal Medial Ridge Among Lizards (Reptilia: Squamata): Its Functional and Taxonomic Significance. The Anatomical Record 297: 2262–2272.
OpenUrl
↵
Čerňanský A, Augé ML. 2019. The Oligocene and Miocene fossil lizards (Reptilia, Squamata) of Central Mongolia. Geodiversitas 41: 811–839.
OpenUrl
↵
Čerňanský A, Syromyatnikova EV. 2021. The first pre-Quaternary fossil record of the clade Mabuyidae with a comment on the enclosure of the Meckelian canal in skinks. Papers in Palaeontology 7: 195–215.
OpenUrl
↵
Chovanec KR. 2014. Non-anguimorph Lizards of the Late Oligocene and Early Miocene of Florida and Implications for the Reorganization of the North American Herpetofauna. Unpublished thesis, East Tennessee State University.
↵
Conrad JL. 2008. Phylogeny and systematics of Squamata (Reptilia) based on morphology. Bulletin of the American Museum of Natural History 310: 1–182.
OpenUrl CrossRef
↵
Conrad JL, Ast JC, Montanari S, Norell MA. 2011. A combined evidence phylogenetic analysis of Anguimorpha (Reptilia: Squamata). Cladistics 27: 230–277.
OpenUrl
Cooke MJ, Stern LA, Banner JL, Mack LE, Stafford TW, Toomey RS. 2003. Precise timing and rate of massive late Quaternary soil denudation. Geology 31: 853.
OpenUrl Abstract/FREE Full Text
↵
Cox DC, Tanner WW. 1977. Osteology and myology of the head and neck regions of Callisaurus, Cophosaurus, Holbrookia, and Uma (Reptilia: Iguanidae). The Great Basin naturalist. 37: 35–56.
OpenUrl
↵
Daza JD, Abdala V, Arias JS, García-López D, Ortiz P. 2012. Cladistic Analysis of Iguania and a Fossil Lizard from the Late Pliocene of Northwestern Argentina. Journal of Herpetology 46: 104–119.
OpenUrl GeoRef
↵
Daza JD, Abdala V, Thomas Richard, Bauer AM. 2008. Skull anatomy of the miniaturized gecko Sphaerodactylus roosevelti (Squamata: Gekkota). Journal of Morphology 269: 1340– 1364.
OpenUrl CrossRef PubMed
↵
Dietl GP, Kidwell SM, Brenner M, Burney DA, Flessa KW, Jackson ST, Koch PL. 2015. Conservation Paleobiology: Leveraging Knowledge of the Past to Inform Conservation and Restoration. Annual Review of Earth and Planetary Sciences 43: 79–103.
OpenUrl CrossRef
↵
Du Bois EP. 1943. Osteology of the Skull of Cnemidophorus. The American Midland Naturalist 30: 510–517.
OpenUrl
↵
Estes R. 1963. A new gerrhonotine lizard from the Pliocene of California. Copeia 1963: 676– 680.
OpenUrl
↵
1. Estes R,
2. Pregill GK
Estes R, de Queiroz K, Gauthier J. 1988. Phylogenetic relationships within Squamata. In: Estes R, Pregill GK, eds. Phylogenetic relationships of the lizard families. Stanford University Press Stanford, 119–281.
↵
Etheridge R. 1959. THE RELATIONSHIPS OF THE ANOLES (REPTILIA:SAURIA:IGUANIDAE) AN INTERPRETATION BASED ON SKELETAL MORPHOLOGY. Unpublished thesis, University of Michigan.
↵
Etheridge R. 1964. The Skeletal Morphology and Systematic Relationships of Sceloporine Lizards. Copeia 1964: 610–631.
OpenUrl
↵
1. Estes R,
2. Pregill GK
Etheridge R, de Queiroz K. 1988. A phylogeny of Iguanidae. In: Estes R, Pregill GK, eds. Phylogenetic relationships of the lizard families. Stanford University Press Stanford, California, 283–367.
↵
1. Gans C,
2. Gaunt AS,
3. Adler K
Evans S. 2008. The skull of lizards and tuatara. In: Gans C, Gaunt AS, Adler K, eds. Biology of the Reptilia, Volume 20, Morphology H. The Skull of Lepidosauria. New York: Society for the Study of Amphibians and Reptiles.
↵
Fisher D. L, Tanner WW. 1970. Osteological and mylogical comparisons of the head and thorax regions of Cnemidophorus tigris septentrionalis Burger and Ameiva undulata parva Barbour and Nobel (Family Teiidae). Brigham Young University Science Bulletin-Biological Series 11: 1–41.
OpenUrl
↵
Frost DR, Etheridge R. 1989. A Phylogenetic analysis and taxonomy of iguanian lizards (Reptilia, Squamata). Laurence, Kansas: Miscellaneous publication of the University of Kansas Museum of Natural History.
↵
Gao K, Norell MA. 1998. Taxonomic Revision of Carusia (Reptilia: Squamata) from the Late Cretaceous of the Gobi Desert and Phylogenetic Relationships of Anguimorphan Lizards. American Museum Novitates 3230: 1–52.
OpenUrl
↵
Gauthier JA. 1982. Fossil xenosaurid and anguid lizards from the early Eocene Wasatch Formation, Southeast Wyoming, and a revision of the Anguioidea. Rocky Mountain Geology 21: 7–54.
OpenUrl Abstract/FREE Full Text
↵
1. Estes R,
2. Pregill GK
Gauthier J, Estes R, De Queiroz K. 1988. A phylogenetic analysis of Lepidosauromorpha. In: Estes R, Pregill GK, eds. Phylogenetic relationships of the lizard families. Stanford University Press Stanford, 15–98.
↵
Gauthier JA, Kearney M, Maisano JA, Rieppel O, Behlke ADB. 2012. Assembling the Squamate Tree of Life: Perspectives from the Phenotype and the Fossil Record. Bulletin of the Peabody Museum of Natural History 53: 3–308.
OpenUrl
GBIF.org. 2023. GBIF Occurrence Downloaded 02 February, doi:10.15468/dl.pergpm.
OpenUrl CrossRef
↵
Good DA. 1987. A Phylogenetic Analysis of Cranial Osteology in the Gerrhonotine Lizards. Journal of Herpetology 21: 285–297.
OpenUrl
↵
Good DA. 1988. The phylogenetic position of fossils assigned to the Gerrhonotinae (Squamata: Anguidae). Journal of Vertebrate Paleontology 8: 188–195.
OpenUrl GeoRef
↵
Gray JA, McDowell MC, Hutchinson MN, Jones MEH. 2017. Geometric Morphometrics Provides an Alternative Approach for Interpreting the Affinity of Fossil Lizard Jaws. Journal of Herpetology 51: 375–382.
OpenUrl
↵
Greer AE. 1970. A subfamilial classification of scincid lizards. Bulletin of the Museum of Comparative Zoology at Harvard College 139: 151–183.
OpenUrl
↵
Greer A. 1974. The genetic relationships of the Scincid lizard genus Leiolopisma and its relatives. Australian Journal of Zoology Supplementary Series 22: 1–67.
OpenUrl
↵
Greer AE. 1985. The relationships of the lizard genera Anelytropsis and Dibamus. Journal of Herpetology 19: 116–156.
OpenUrl CrossRef Web of Science
↵
Guerra C, Montero R. 2009. The skull of Vanzosaura rubricauda (Squamata: Gymnophthalmidae). Acta Zoologica 90: 359–371.
OpenUrl
↵
Harvey VL, LeFebvre MJ, deFrance SD, Toftgaard C, Drosou K, Kitchener AC, Buckley M. 2019. Preserved collagen reveals species identity in archaeological marine turtle bones from Caribbean and Florida sites. Royal Society Open Science 6: 191137.
OpenUrl
Hernández Morales C, Peloso PLV, Bolívar García W, Daza JD. 2019. Skull Morphology of the Lizard Ptychoglossus vallensis (Squamata: Alopoglossidae) With Comments on the Variation Within Gymnophthalmoidea. The Anatomical Record 302: 1074–1092.
OpenUrl
↵
Hollenshead MG, Mead JI. 2006. Early Pliocene Crotaphytus and Gambelia (Squamata: Crotaphytidae) from the Panaca Formation of Southeastern Nevada. Journal of Herpetology 40: 566–569.
OpenUrl
↵
Holman JA. 1969. The Pleistocene Amphibians and Reptiles of Texas. Michigan State University Publications 4: 161–192.
OpenUrl
↵
Holman JA. 1995. Pleistocene amphibians and reptiles in North America. New York: Oxford University Press.
↵
Holovacs NT, Daza JD, Guerra C, Stanley EL, Montero R. 2020. You Can’t Run, but You Can Hide: The Skeleton of the Sand-Swimmer Lizard Calyptommatus leiolepis (Squamata: Gymnophthalmidae). The Anatomical Record 303: 1305–1326.
OpenUrl
↵
Hoyos J. 1998. A reappraisal of the phylogeny of lizards of the family Gymnophthalmidae (Sauria, Scincomorpha). Revista Española de Herpetología 12: 27–43.
OpenUrl
↵
Jerez A, Sánchez-Martínez PM, Guerra-Fuentes RA. 2015. Embryonic skull development in the neotropical viviparous skink Mabuya (Squamata: Scincidae). Acta zoológica mexicana 31: 391–402.
OpenUrl
↵
Kehlmaier C, Barlow A, Hastings AK, Vamberger M, Paijmans JLA, Steadman DW, Albury NA, Franz R, Hofreiter M, Fritz U. 2017. Tropical ancient DNA reveals relationships of the extinct Bahamian giant tortoise Chelonoidis alburyorum. Proceedings of the Royal Society B: Biological Sciences 284: 20162235.
OpenUrl CrossRef PubMed
↵
Klembara J. 2015. New finds of anguines (Squamata, Anguidae) from the Early Miocene of Northwest Bohemia (Czech Republic). Paläontologische Zeitschrift 89: 171–195.
OpenUrl
↵
Klembara J, Dobiašová K, Hain M, Yaryhin O. 2017. Skull Anatomy and Ontogeny of Legless Lizard Pseudopus apodus (Pallas, 1775): Heterochronic Influences on Form. The Anatomical Record 300: 460–502.
OpenUrl
↵
Klembara J, Hain M, Dobiašová K. 2014. Comparative Anatomy of the Lower Jaw and Dentition of Pseudopus apodus and the Interrelationships of Species of Subfamily Anguinae (Anguimorpha, Anguidae). The Anatomical Record 297: 516–544.
OpenUrl
↵
Kluge AG. 1962. Comparative osteology of the eublepharid lizard genus Coleonyx Gray. Journal of Morphology 110: 299–332.
OpenUrl
↵
Kluge AG. 1967. Higher taxonomic categories of gekkonid lizards and their evolution. Bulletin of the AMNH 135: 1–59 + Plates 1–5.
OpenUrl
↵
Lang M. 1989. Phylogenetic and biogeographic patterns of basiliscine iguanians: Reptilia, Squamata, ‘Iguanidae’. Bonn: Zoologisches Forschungsinstitut und Museum Alexander Koenig.
↵
1. J Mead
Ledesma DT, Scarpetta SG. 2018.The skull of the gerrhonotine lizard Elgaria panamintina (Squamata: Anguidae) ( J Mead, Ed.). PLOS ONE 13: e0199584.
OpenUrl
↵
Ledesma DT, Scarpetta SG, Bell CJ. 2021. Variation in the skulls of Elgaria and Gerrhonotus (Anguidae, Gerrhonotinae) and implications for phylogenetics and fossil identification. PeerJ 9: e11602.
OpenUrl
↵
Mahler DL, Kearney M. 2006. The Palatal Dentition in Squamate Reptiles: Morphology, Development, Attachment, and Replacement. Fieldiana Zoology 2006: 1–61.
OpenUrl
↵
Maisano JA. 2002a. Postnatal skeletal ontogeny in Callisaurus draconoides and Uta stansburiana (Iguania: Phrynosomatidae). Journal of Morphology 251: 114–139.
OpenUrl CrossRef PubMed Web of Science
↵
Maisano JA. 2002b. Postnatal skeletal ontogeny in five Xantusiids (Squamata: Scleroglossa). Journal of Morphology 254: 1–38.
OpenUrl CrossRef PubMed
↵
Mausfeld P, Schmitz A, Böhme W, Misof B, Vrcibradic D, Rocha CFD. 2002. Phylogenetic Affinities of Mabuya atlantica Schmidt, 1945, Endemic to the Atlantic Ocean Archipelago of Fernando de Noronha (Brazil): Necessity of Partitioning the Genus Mabuya Fitzinger, 1826 (Scincidae: Lygosominae). Zoologischer Anzeiger - A Journal of Comparative Zoology 241: 281–293.
OpenUrl
↵
McDowell SB, Bogert CM. 1954. The systematic position of Lanthanotus and the affinities of the anguinomorphan lizards. Bulletin of the AMNH 105: 1–142 + plates 1–16.
OpenUrl
↵
McGuire JA. 1996. Phylogenetic systematics of crotaphytid lizards (Reptilia: Iguania: Crotaphytidae). Bulletin of Carnegie Museum of Natural History 32: 1–143.
OpenUrl
↵
Mead J. 1988. Herpetofauna from Danger Cave, Last Supper Cave, and Hanging Rock Shelter. Anthropological Papers of the American Museum of Natural History 66: 116–120.
OpenUrl
↵
Mead J, Bell CJ. 2001. Pliocene amphibians and reptiles from Clark County, Nevada. Bulletin of the Southern California Academy of Sciences 100: 1–11.
OpenUrl
↵
Mead JI, Hollenshead MG, Swift SL, Bell CJ, Baynes A. 2008. Pygopus (Squamata: Pygopodidae) from mid-Holocene cave deposits, Western and South Australia. Records of the Western Australian Museum 25: 87–93.
OpenUrl GeoRef
↵
Mead JI, J Arroyo Cabrales, Johnson E. 1999. Pleistocene Lizards (Reptilia: Squamata) from San Josecito Cave, Nuevo León, México. Copeia 1999: 163–173.
OpenUrl
Mead JI, Roth EL, Van Devender TR, Steadman DW. 1984. The late Wisconsinan vertebrate fauna from Deadman Cave, southern Arizona. Transactions of the San Diego Society of Natural History 20: 247–276.
OpenUrl
↵
Meszoely CAM. 1970. North American fossil anguid lizards. Bulletin of the Museum of Comparative Zoology at Harvard College. 139: 87–149.
OpenUrl
↵
Meyers JJ, Herrel A, Nishikawa KC. 2006. Morphological correlates of ant eating in horned lizards (Phrynosoma). Biological Journal of the Linnean Society 89: 13–24.
OpenUrl
↵
Montanucci RR. 1987. A phylogenetic study of the horned lizards, genus Phrynosoma, based on skeletal and external morphology. Contributions in science 390: 1–36.
OpenUrl
Nash DF. A comparative study of the head and thoracic osteology and myology of the skinks, Eumeces gilberti Van Denburgh and Eumeces skiltonianus (Baird and Girard). Unpublished thesis, Brigham Young University.
↵
Norell MA. 1989. Late Cenozoic lizards of the Anza Borrego Desert, California. Natural History Museum of Los Angeles County Contributions in Science 414: 1–31.
OpenUrl
↵
Norris KS, Lowe CH. 1951. A study of the osteology and musculature of Phrynosoma m’callii pertinent to its systematic status. Bulletin of the Chicago Academy of Sciences 9: 117–125.
OpenUrl
↵
Nydam RL, Eaton JG, Sankey J. 2007. NEW TAXA OF TRANSVERSELY-TOOTHED LIZARDS (SQUAMATA: SCINCOMORPHA) AND NEW INFORMATION ON THE EVOLUTIONARY HISTORY OF “TEIIDS”. Journal of Paleontology 81: 538–549.
OpenUrl Abstract/FREE Full Text
↵
de Oca ANM, Arenas-Moreno D, Beltrán-Sánchez E, Leaché AD. 2014. A New Species of Horned Lizard (Genus Phrynosoma) from Guerrero, México, with an Updated Multilocus Phylogeny. Herpetologica 70: 241–257.
OpenUrl CrossRef
↵
Oelrich TM. 1956. The Anatomy of the Head of Ctenosaura pectinata (Iguanidae). Miscellaneous Publications Museum Of Zoology, University Of Michigan 94: 1–122.
OpenUrl
↵
Paluh DJ, Bauer AM. 2017. Comparative skull anatomy of terrestrial and crevice-dwelling Trachylepis skinks (Squamata: Scincidae) with a survey of resources in scincid cranial osteology. PLOS ONE 12: e0184414.
OpenUrl CrossRef
↵
Parmley D. 1988. Middle Holocene Herpetofauna of Klein Cave, Kerr County, Texas. The Southwestern Naturalist 33: 378–382.
OpenUrl GeoRef
↵
Parmley D, Bahn JR. 2012. LATE PLEISTOCENE LIZARDS FROM FOWLKES CAVE, CULBERSON COUNTY, TEXAS. The Southwestern Naturalist 57: 435–441.
OpenUrl
↵
Powell GL, Russell AP, Jamniczky HA, Hallgrímsson B. 2017. Shape Variation in the Dermatocranium of the Greater Short-Horned Lizard Phrynosoma hernandesi (Reptilia: Squamata: Phrynosomatidae). Evolutionary Biology 44: 240–260.
OpenUrl
↵
Pregill GK. 1981. Late Pleistocene herpetofaunas from Puerto Rico. Miscellaneous publication - University of Kansas, Museum of Natural History 71: 1–72.
OpenUrl
↵
Pregill GK. 1988. Late Holocene fossil vertebrates from Burma Quarry, Antigua, Lesser Antilles. Smithsonian Contributions to Zoology 463: 1–27.
OpenUrl
↵
Pregill GK. 1992. Systematics of the West Indian lizard genus Leiocephalus (Squamata: Iguania: Tropiduridae). Miscellaneous publication - University of Kansas, Museum of Natural History 84: 1–69.
OpenUrl
↵
Presch W. 1969. Evolutionary Osteology and Relationships of the Horned Lizard Genus Phrynosoma (Family Iguanidae). Copeia 1969: 250–275.
OpenUrl
↵
de Queiroz K. 1987. Phylogenetic Systematics of iguanine lizards. University of California Publications in Zoology 118: xii + 1–203.
OpenUrl
↵
Ramm T, Thorn KM, A. Hipsley C, Müller J, Hocknull S, Melville J. 2021. Herpetofaunal diversity changes with climate: evidence from the Quaternary of McEachern’s Deathtrap Cave, southeastern Australia. Journal of Vertebrate Paleontology 41: e2009844.
OpenUrl
↵
Reed FA, Kontanis EJ, Kennedy KAR, Aquadro CF. 2003. Brief communication: Ancient DNA prospects from Sri Lankan highland dry caves support an emerging global pattern. American Journal of Physical Anthropology 121: 112–116.
OpenUrl CrossRef PubMed Web of Science
↵
Rieppel Olivier. 1980. The phylogeny of anguinomorph lizards. Basel, Boston: Birkhäuser Verlag.
↵
Roscito JG, Rodrigues MT. 2010. Comparative cranial osteology of fossorial lizards from the tribe gymnophthalmini (Squamata, Gymnophthalmidae). Journal of Morphology 271: 1352– 1365.
OpenUrl PubMed
↵
Roth EL. 1972. Late Pleistocene Mammals From Klein Cave, Kerr County, Texas. The Texas Journal of Science 24: 75–84.
OpenUrl
↵
Savage JM. 1963. Studies on the lizard family Xantusiidae. IV. The genera. Contributions in Science 71: 1–38.
OpenUrl
↵
Scarpetta S. 2018. The earliest known occurrence of Elgaria (Squamata: Anguidae) and a minimum age for crown Gerrhonotinae: Fossils from the Split Rock Formation, Wyoming, USA. Palaeontologicia Electronica 21.1.1FC: 1–9.
OpenUrl
↵
Scarpetta SG. 2019. The first known fossil Uma: ecological evolution and the origins of North American fringe-toed lizards. BMC Evolutionary Biology 19(178): 1–22.
OpenUrl CrossRef
↵
Scarpetta SG. 2020. Unusual lizard fossil from the Miocene of Nebraska and a minimum age for cnemidophorine teiids. Royal Society Open Science 7(200317): 1–12.
OpenUrl
↵
Scarpetta SG. 2021. Iguanian lizards from the Split Rock Formation, Wyoming: exploring the modernization of the North American lizard fauna. Journal of Systematic Palaeontology 19: 221–251.
OpenUrl
↵
Scarpetta SG, Ledesma DT, Bell CJ. 2021. A new extinct species of alligator lizard (Squamata: Elgaria) and an expanded perspective on the osteology and phylogeny of Gerrhonotinae. BMC Ecology and Evolution 21(184): 1–58.
OpenUrl CrossRef
↵
Seersholm FV, Werndly DJ, Grealy A, Johnson T, Keenan Early EM, Lundelius EL, Winsborough B, Farr GE, Toomey R, Hansen AJ, Shapiro B, Waters MR, McDonald G, Linderholm A, Stafford TW, Bunce M. 2020. Rapid range shifts and megafaunal extinctions associated with late Pleistocene climate change. Nature Communications 11(2770): 1–10.
OpenUrl
↵
Smith KT. 2006. A diverse new assemblage of Late Eocene squamates (Reptilia) from the Chadron Formation of North Dakota. Palaeontologicia Electronica 9(2;5A): 1–44.
OpenUrl
↵
Smith KT. 2009a. A new lizard assemblage from the earliest Eocene (Zone Wa0) of the bighorn basin, Wyoming, USA: Biogeography during the warmest interval of the Cenozoic. Journal of Systematic Palaeontology 7: 299–358.
OpenUrl
↵
Smith KT. 2009b. Eocene Lizards of the Clade Geiseltaliellus from Messel and Geiseltal, Germany, and the Early Radiation of Iguanidae (Reptilia: Squamata). Bulletin of the Peabody Museum of Natural History 50: 219–306.
OpenUrl
↵
Smith KT. 2011. The Evolution of Mid-Latitude Faunas During the Eocene: Late Eocene Lizards of the Medicine Pole Hills Reconsidered. Bulletin of the Peabody Museum of Natural History 52: 3–105.
OpenUrl
↵
1. Gower DG,
2. Zaher H
Smith KT, Georgalis GL. 2022. The Diversity and Distribution of Palaeogene Snakes. In: Gower DG, Zaher H, eds. The Origin and Early Evolutionary History of Snakes. Cambridge, United Kingdon: Cambridge University Press, 55–84.
↵
Smith FA, Tomé CP, Elliott Smith EA, Lyons SK, Newsome SD, Stafford TW. 2016. Unraveling the consequences of the terminal Pleistocene megafauna extinction on mammal community assembly. Ecography 39: 223–239.
OpenUrl CrossRef
↵
Syromyatnikova E, Aranda E. 2022. A record of galliwasp (Diploglossidae: Diploglossus) from the Pleistocene of Cuba. Historical Biology: 1–5. doi:10.1080/08912963.2022.2077108.
OpenUrl CrossRef
↵
Tarazona OA, Fabrezi M, Ramírez-Pinilla MP. 2008. Cranial morphology of Bachia bicolor (Squamata: Gymnophthalmidae) and its postnatal development. Zoological Journal of the Linnean Society 152: 775–792.
OpenUrl
↵
Taylor EH. 1940. Palatal sesamoid bones and palatal teeth in Cnemidophorus, with notes on these teeth in other saurian genera. Proceedings of the Biological Society of Washington 53: 119–123.
OpenUrl
↵
Tedesco ME, Krause L, Alvarez BB. 1999. Descripción del sincraneo de Ameiva ameiva (Linnaeus) (Squamata, Teiidae). Revista Brasileira de Zoologia 16: 1025–1044.
OpenUrl
↵
Toerien MJ. 1950. The cranial morphology of the Californian lizard-Anniella pulchra Gray. South African Journal of Science 46: 321–342.
OpenUrl
↵
Tollis M, Boissinot S. 2014. Genetic variation in the green anole lizard (Anolis carolinensis) reveals island refugia and a fragmented Florida during the quaternary. Genetica 142: 59–72.
OpenUrl CrossRef PubMed Web of Science
↵
Toomey RS. 1993. Late Pleistocene and Holocene faunal and environmental changes at Hall’s Cave, Kerr County, Texas. Unpublished thesis, The University of Texas at Austin.
Torres-Carvajal O. 2003. Cranial Osteology of the Andean Lizard Stenocercus guentheri (Squamata: Tropiduridae) and Its Postembryonic Development. Journal of Morphology 255: 94– 113.
OpenUrl PubMed
↵
Townsend VR, Akin JA, Felgenhauer BE, Dauphine J, Kidder SA. 1999. Dentition of the Ground Skink, Scincella lateralis (Sauria, Scincidae). Copeia 1999: 783–788.
OpenUrl
↵
Vasilyan D, Bukhsianidze M. 2020. The fossil record of the genus Varanus from the Southern Caucasus (Armenia, Georgia). PeerJ 8: e8322.
OpenUrl
↵
Villa A, Delfino M. 2019. A comparative atlas of the skull osteology of European lizards (Reptilia: Squamata). Zoological Journal of the Linnean Society 187: 829–928.
OpenUrl
↵
Waters MR, Keene JL, Prewitt ER, Everett ME, Laughlin T, Stafford TW. 2021. Late Quaternary geology, archaeology, and geoarchaeology of Hall’s Cave, Texas. Quaternary Science Reviews 274: 107276.
OpenUrl
Yánez-Muñoz MH, Torres-Carvajal O, Reyes-Puig JP, Urgiles-Merchán MA, Koch C. 2021. A new and very spiny lizard (Gymnophthalmidae: Echinosaura) from the Andes in northwestern Ecuador. PeerJ 9: e12523.
OpenUrl

View the discussion thread.

Posted July 26, 2023.

Download PDF

Supplementary Material

Citation Tools

Subject Area

Paleontology

Subject Areas

All Articles

Animal Behavior and Cognition (5709)
Biochemistry (12939)
Bioengineering (9839)
Bioinformatics (31555)
Biophysics (16267)
Cancer Biology (13346)
Cell Biology (19024)
Clinical Trials (138)
Developmental Biology (10314)
Ecology (15320)
Epidemiology (2067)
Evolutionary Biology (19561)
Genetics (12979)
Genomics (17941)
Immunology (13060)
Microbiology (30497)
Molecular Biology (12719)
Neuroscience (66592)
Paleontology (490)
Pathology (2061)
Pharmacology and Toxicology (3548)
Physiology (5534)
Plant Biology (11403)
Scientific Communication and Education (1751)
Synthetic Biology (3169)
Systems Biology (7835)
Zoology (1769)

[1] ↵
Auffenberg W. 1956. ADDITIONAL RECORDS OF PLEISTOCENE LIZARDS FROM FLORIDA. Quarterly Journal of the Florida Academy of Sciences 19: 157–167.
OpenUrl

[2] ↵
Wright HE,
Frey DG
Auffenberg W, Milstead WW. 1965. REPTILES IN THE QUATERNARY OF NORTH AMERICA. In: Wright HE, Frey DG, eds. The Quaternary of the U.S. Princeton University Press, 557–568.

[3] Wright HE,

[4] Frey DG

[5] ↵
Bell CJ. 1993. Fossil lizards from the Elsinore fault zone, Riverside County, California PaleoBios 15: 18–26.
OpenUrl

[6] ↵
Bell C, Evans S, Maisano J. 2003. The skull of the gymnophthalmid lizard Neusticurus ecpleopus (Reptilia: Squamata). Zoological Journal of the Linnean Society 139: 283–304.
OpenUrl

[7] ↵
Bell CJ, Gauthier JA, Bever GS. 2010. Covert biases, circularity, and apomorphies: A critical look at the North American Quaternary Herpetofaunal Stability Hypothesis. Quaternary International 217: 30–36.
OpenUrl CrossRef GeoRef Web of Science

[8] ↵
Barnosky AD
Bell CJ, Head JJ, Mead JI. 2004. Synopsis of the herpetofauna from Porcupine Cave. In: Barnosky AD, ed. Biodiversity Response to Climate Change in the Middle Pleistocene: the Porcupine Cave Fauna from Colorado. Berkeley, California: University of California Press, 117–126.

[9] Barnosky AD

[10] ↵
Bhullar BAS. 2010. Cranial osteology of Exostinus serratus (Squamata: Anguimorpha), fossil sister taxon to the enigmatic clade Xenosaurus. Zoological Journal of the Linnean Society 159: 921–953.
OpenUrl

[11] ↵
Bhullar BAS. 2011. The Power and Utility Of Morphological Characters In Systematics: A Fully Resolved Phylogeny of Xenosaurus and Its Fossil Relatives (Squamata: Anguimorpha). Bulletin of the Museum of Comparative Zoology 160: 65–181.
OpenUrl

[12] ↵
Bochaton C, Boistel R, Casagrande F, Grouard S, Bailon S. 2016a. A fossil Diploglossus (Squamata, Anguidae) lizard from Basse-Terre and Grande-Terre Islands (Guadeloupe, French West Indies). Scientific Reports 6: 28475.
OpenUrl

[13] ↵
Bochaton C, Boistel R, Grouard S, Ineich I, Tresset A, Bailon S. 2019. Evolution, diversity and interactions with past human populations of recently extinct Pholidoscelis lizards (Squamata: Teiidae) from the Guadeloupe Islands (French West-Indies). Historical Biology 31: 140–156.
OpenUrl

[14] ↵
Bochaton C, Charles L, Lenoble A. 2021. Historical and fossil evidence of an extinct endemic species of Leiocephalus (Squamata: Leiocephalidae) from the Guadeloupe Islands. Zootaxa 4927: 383–409.
OpenUrl

[15] ↵
Bochaton C, Daza JD, Lenoble A. 2018. Identifying Gecko Species from Lesser Antillean Paleontological Assemblages: Intraspecific Osteological Variation within and Interspecific Osteological Differences between Thecadactylus rapicauda (Houttuyn, 1782) (Phyllodactylidae) and Hemidactylus mabouia (Moreau de Jonnès, 1818) (Gekkonidae). Journal of Herpetology 52: 313–320.
OpenUrl

[16] ↵
Bochaton C, Grouard S, Breuil M, Ineich I, Tresset A, Bailon S. 2016b. Osteological Differentiation of the Iguana Laurenti, 1768 (Squamata: Iguanidae) Species: Iguana iguana (Linnaeus, 1758) and Iguana delicatissima Laurenti, 1768, with some Comments on their Hybrids. Journal of Herpetology 50: 295–305.
OpenUrl

[17] ↵
Mead JI,
Meltzer DJ
Brewer. 1985. Herpetofaunas in the late Pleistocene: Extinctions and extralimital forms. In: Mead JI, Meltzer DJ, eds. Environments and extinctions: Man in late glacial North America. Orono, MA: Center for the Study of Early Man, 31–52.

[18] Mead JI,

[19] Meltzer DJ

[20] ↵
Burbrink FT, Grazziotin FG, Pyron RA, Cundall D, Donnellan S, Irish F, Keogh JS, Kraus F, Murphy RW, Noonan B, Raxworthy CJ, Ruane S, Lemmon AR, Lemmon EM, Zaher H. 2020. Interrogating Genomic-Scale Data for Squamata (Lizards, Snakes, and Amphisbaenians) Shows no Support for Key Traditional Morphological Relationships. Systematic Biology 69: 502–520.
OpenUrl

[21] ↵
Campbell-Staton SC, Goodman RM, Backström N, Edwards SV, Losos JB, Kolbe JJ. 2012. Out of Florida: mtDNA reveals patterns of migration and Pleistocene range expansion of the Green Anole lizard (Anolis carolinensis). Ecology and Evolution 2: 2274–2284.
OpenUrl

[22] ↵
Čerňanský A, Smith KT, Klembara J. 2014. Variation in the Position of the Jugal Medial Ridge Among Lizards (Reptilia: Squamata): Its Functional and Taxonomic Significance. The Anatomical Record 297: 2262–2272.
OpenUrl

[23] ↵
Čerňanský A, Augé ML. 2019. The Oligocene and Miocene fossil lizards (Reptilia, Squamata) of Central Mongolia. Geodiversitas 41: 811–839.
OpenUrl

[24] ↵
Čerňanský A, Syromyatnikova EV. 2021. The first pre-Quaternary fossil record of the clade Mabuyidae with a comment on the enclosure of the Meckelian canal in skinks. Papers in Palaeontology 7: 195–215.
OpenUrl

[25] ↵
Chovanec KR. 2014. Non-anguimorph Lizards of the Late Oligocene and Early Miocene of Florida and Implications for the Reorganization of the North American Herpetofauna. Unpublished thesis, East Tennessee State University.

[26] ↵
Conrad JL. 2008. Phylogeny and systematics of Squamata (Reptilia) based on morphology. Bulletin of the American Museum of Natural History 310: 1–182.
OpenUrl CrossRef

[27] ↵
Conrad JL, Ast JC, Montanari S, Norell MA. 2011. A combined evidence phylogenetic analysis of Anguimorpha (Reptilia: Squamata). Cladistics 27: 230–277.
OpenUrl

[28] Cooke MJ, Stern LA, Banner JL, Mack LE, Stafford TW, Toomey RS. 2003. Precise timing and rate of massive late Quaternary soil denudation. Geology 31: 853.
OpenUrl Abstract/FREE Full Text

[29] ↵
Cox DC, Tanner WW. 1977. Osteology and myology of the head and neck regions of Callisaurus, Cophosaurus, Holbrookia, and Uma (Reptilia: Iguanidae). The Great Basin naturalist. 37: 35–56.
OpenUrl

[30] ↵
Daza JD, Abdala V, Arias JS, García-López D, Ortiz P. 2012. Cladistic Analysis of Iguania and a Fossil Lizard from the Late Pliocene of Northwestern Argentina. Journal of Herpetology 46: 104–119.
OpenUrl GeoRef

[31] ↵
Daza JD, Abdala V, Thomas Richard, Bauer AM. 2008. Skull anatomy of the miniaturized gecko Sphaerodactylus roosevelti (Squamata: Gekkota). Journal of Morphology 269: 1340– 1364.
OpenUrl CrossRef PubMed

[32] ↵
Dietl GP, Kidwell SM, Brenner M, Burney DA, Flessa KW, Jackson ST, Koch PL. 2015. Conservation Paleobiology: Leveraging Knowledge of the Past to Inform Conservation and Restoration. Annual Review of Earth and Planetary Sciences 43: 79–103.
OpenUrl CrossRef

[33] ↵
Du Bois EP. 1943. Osteology of the Skull of Cnemidophorus. The American Midland Naturalist 30: 510–517.
OpenUrl

[34] ↵
Estes R. 1963. A new gerrhonotine lizard from the Pliocene of California. Copeia 1963: 676– 680.
OpenUrl

[35] ↵
Estes R,
Pregill GK
Estes R, de Queiroz K, Gauthier J. 1988. Phylogenetic relationships within Squamata. In: Estes R, Pregill GK, eds. Phylogenetic relationships of the lizard families. Stanford University Press Stanford, 119–281.

[36] Estes R,

[37] Pregill GK

[38] ↵
Etheridge R. 1959. THE RELATIONSHIPS OF THE ANOLES (REPTILIA:SAURIA:IGUANIDAE) AN INTERPRETATION BASED ON SKELETAL MORPHOLOGY. Unpublished thesis, University of Michigan.

[39] ↵
Etheridge R. 1964. The Skeletal Morphology and Systematic Relationships of Sceloporine Lizards. Copeia 1964: 610–631.
OpenUrl

[40] ↵
Estes R,
Pregill GK
Etheridge R, de Queiroz K. 1988. A phylogeny of Iguanidae. In: Estes R, Pregill GK, eds. Phylogenetic relationships of the lizard families. Stanford University Press Stanford, California, 283–367.

[41] Estes R,

[42] Pregill GK

[43] ↵
Gans C,
Gaunt AS,
Adler K
Evans S. 2008. The skull of lizards and tuatara. In: Gans C, Gaunt AS, Adler K, eds. Biology of the Reptilia, Volume 20, Morphology H. The Skull of Lepidosauria. New York: Society for the Study of Amphibians and Reptiles.

[44] Gans C,

[45] Gaunt AS,

[46] Adler K

[47] ↵
Fisher D. L, Tanner WW. 1970. Osteological and mylogical comparisons of the head and thorax regions of Cnemidophorus tigris septentrionalis Burger and Ameiva undulata parva Barbour and Nobel (Family Teiidae). Brigham Young University Science Bulletin-Biological Series 11: 1–41.
OpenUrl

[48] ↵
Frost DR, Etheridge R. 1989. A Phylogenetic analysis and taxonomy of iguanian lizards (Reptilia, Squamata). Laurence, Kansas: Miscellaneous publication of the University of Kansas Museum of Natural History.

[49] ↵
Gao K, Norell MA. 1998. Taxonomic Revision of Carusia (Reptilia: Squamata) from the Late Cretaceous of the Gobi Desert and Phylogenetic Relationships of Anguimorphan Lizards. American Museum Novitates 3230: 1–52.
OpenUrl

[50] ↵
Gauthier JA. 1982. Fossil xenosaurid and anguid lizards from the early Eocene Wasatch Formation, Southeast Wyoming, and a revision of the Anguioidea. Rocky Mountain Geology 21: 7–54.
OpenUrl Abstract/FREE Full Text

[51] ↵
Estes R,
Pregill GK
Gauthier J, Estes R, De Queiroz K. 1988. A phylogenetic analysis of Lepidosauromorpha. In: Estes R, Pregill GK, eds. Phylogenetic relationships of the lizard families. Stanford University Press Stanford, 15–98.

[52] Estes R,

[53] Pregill GK

[54] ↵
Gauthier JA, Kearney M, Maisano JA, Rieppel O, Behlke ADB. 2012. Assembling the Squamate Tree of Life: Perspectives from the Phenotype and the Fossil Record. Bulletin of the Peabody Museum of Natural History 53: 3–308.
OpenUrl

[55] GBIF.org. 2023. GBIF Occurrence Downloaded 02 February, doi:10.15468/dl.pergpm.
OpenUrl CrossRef

[56] ↵
Good DA. 1987. A Phylogenetic Analysis of Cranial Osteology in the Gerrhonotine Lizards. Journal of Herpetology 21: 285–297.
OpenUrl

[57] ↵
Good DA. 1988. The phylogenetic position of fossils assigned to the Gerrhonotinae (Squamata: Anguidae). Journal of Vertebrate Paleontology 8: 188–195.
OpenUrl GeoRef

[58] ↵
Gray JA, McDowell MC, Hutchinson MN, Jones MEH. 2017. Geometric Morphometrics Provides an Alternative Approach for Interpreting the Affinity of Fossil Lizard Jaws. Journal of Herpetology 51: 375–382.
OpenUrl

[59] ↵
Greer AE. 1970. A subfamilial classification of scincid lizards. Bulletin of the Museum of Comparative Zoology at Harvard College 139: 151–183.
OpenUrl

[60] ↵
Greer A. 1974. The genetic relationships of the Scincid lizard genus Leiolopisma and its relatives. Australian Journal of Zoology Supplementary Series 22: 1–67.
OpenUrl

[61] ↵
Greer AE. 1985. The relationships of the lizard genera Anelytropsis and Dibamus. Journal of Herpetology 19: 116–156.
OpenUrl CrossRef Web of Science

[62] ↵
Guerra C, Montero R. 2009. The skull of Vanzosaura rubricauda (Squamata: Gymnophthalmidae). Acta Zoologica 90: 359–371.
OpenUrl

[63] ↵
Harvey VL, LeFebvre MJ, deFrance SD, Toftgaard C, Drosou K, Kitchener AC, Buckley M. 2019. Preserved collagen reveals species identity in archaeological marine turtle bones from Caribbean and Florida sites. Royal Society Open Science 6: 191137.
OpenUrl

[64] Hernández Morales C, Peloso PLV, Bolívar García W, Daza JD. 2019. Skull Morphology of the Lizard Ptychoglossus vallensis (Squamata: Alopoglossidae) With Comments on the Variation Within Gymnophthalmoidea. The Anatomical Record 302: 1074–1092.
OpenUrl

[65] ↵
Hollenshead MG, Mead JI. 2006. Early Pliocene Crotaphytus and Gambelia (Squamata: Crotaphytidae) from the Panaca Formation of Southeastern Nevada. Journal of Herpetology 40: 566–569.
OpenUrl

[66] ↵
Holman JA. 1969. The Pleistocene Amphibians and Reptiles of Texas. Michigan State University Publications 4: 161–192.
OpenUrl

[67] ↵
Holman JA. 1995. Pleistocene amphibians and reptiles in North America. New York: Oxford University Press.

[68] ↵
Holovacs NT, Daza JD, Guerra C, Stanley EL, Montero R. 2020. You Can’t Run, but You Can Hide: The Skeleton of the Sand-Swimmer Lizard Calyptommatus leiolepis (Squamata: Gymnophthalmidae). The Anatomical Record 303: 1305–1326.
OpenUrl

[69] ↵
Hoyos J. 1998. A reappraisal of the phylogeny of lizards of the family Gymnophthalmidae (Sauria, Scincomorpha). Revista Española de Herpetología 12: 27–43.
OpenUrl

[70] ↵
Jerez A, Sánchez-Martínez PM, Guerra-Fuentes RA. 2015. Embryonic skull development in the neotropical viviparous skink Mabuya (Squamata: Scincidae). Acta zoológica mexicana 31: 391–402.
OpenUrl

[71] ↵
Kehlmaier C, Barlow A, Hastings AK, Vamberger M, Paijmans JLA, Steadman DW, Albury NA, Franz R, Hofreiter M, Fritz U. 2017. Tropical ancient DNA reveals relationships of the extinct Bahamian giant tortoise Chelonoidis alburyorum. Proceedings of the Royal Society B: Biological Sciences 284: 20162235.
OpenUrl CrossRef PubMed

[72] ↵
Klembara J. 2015. New finds of anguines (Squamata, Anguidae) from the Early Miocene of Northwest Bohemia (Czech Republic). Paläontologische Zeitschrift 89: 171–195.
OpenUrl

[73] ↵
Klembara J, Dobiašová K, Hain M, Yaryhin O. 2017. Skull Anatomy and Ontogeny of Legless Lizard Pseudopus apodus (Pallas, 1775): Heterochronic Influences on Form. The Anatomical Record 300: 460–502.
OpenUrl

[74] ↵
Klembara J, Hain M, Dobiašová K. 2014. Comparative Anatomy of the Lower Jaw and Dentition of Pseudopus apodus and the Interrelationships of Species of Subfamily Anguinae (Anguimorpha, Anguidae). The Anatomical Record 297: 516–544.
OpenUrl

[75] ↵
Kluge AG. 1962. Comparative osteology of the eublepharid lizard genus Coleonyx Gray. Journal of Morphology 110: 299–332.
OpenUrl

[76] ↵
Kluge AG. 1967. Higher taxonomic categories of gekkonid lizards and their evolution. Bulletin of the AMNH 135: 1–59 + Plates 1–5.
OpenUrl

[77] ↵
Lang M. 1989. Phylogenetic and biogeographic patterns of basiliscine iguanians: Reptilia, Squamata, ‘Iguanidae’. Bonn: Zoologisches Forschungsinstitut und Museum Alexander Koenig.

[78] ↵
J Mead
Ledesma DT, Scarpetta SG. 2018.The skull of the gerrhonotine lizard Elgaria panamintina (Squamata: Anguidae) ( J Mead, Ed.). PLOS ONE 13: e0199584.
OpenUrl

[79] J Mead

[80] ↵
Ledesma DT, Scarpetta SG, Bell CJ. 2021. Variation in the skulls of Elgaria and Gerrhonotus (Anguidae, Gerrhonotinae) and implications for phylogenetics and fossil identification. PeerJ 9: e11602.
OpenUrl

[81] ↵
Mahler DL, Kearney M. 2006. The Palatal Dentition in Squamate Reptiles: Morphology, Development, Attachment, and Replacement. Fieldiana Zoology 2006: 1–61.
OpenUrl

[82] ↵
Maisano JA. 2002a. Postnatal skeletal ontogeny in Callisaurus draconoides and Uta stansburiana (Iguania: Phrynosomatidae). Journal of Morphology 251: 114–139.
OpenUrl CrossRef PubMed Web of Science

[83] ↵
Maisano JA. 2002b. Postnatal skeletal ontogeny in five Xantusiids (Squamata: Scleroglossa). Journal of Morphology 254: 1–38.
OpenUrl CrossRef PubMed

[84] ↵
Mausfeld P, Schmitz A, Böhme W, Misof B, Vrcibradic D, Rocha CFD. 2002. Phylogenetic Affinities of Mabuya atlantica Schmidt, 1945, Endemic to the Atlantic Ocean Archipelago of Fernando de Noronha (Brazil): Necessity of Partitioning the Genus Mabuya Fitzinger, 1826 (Scincidae: Lygosominae). Zoologischer Anzeiger - A Journal of Comparative Zoology 241: 281–293.
OpenUrl

[85] ↵
McDowell SB, Bogert CM. 1954. The systematic position of Lanthanotus and the affinities of the anguinomorphan lizards. Bulletin of the AMNH 105: 1–142 + plates 1–16.
OpenUrl

[86] ↵
McGuire JA. 1996. Phylogenetic systematics of crotaphytid lizards (Reptilia: Iguania: Crotaphytidae). Bulletin of Carnegie Museum of Natural History 32: 1–143.
OpenUrl

[87] ↵
Mead J. 1988. Herpetofauna from Danger Cave, Last Supper Cave, and Hanging Rock Shelter. Anthropological Papers of the American Museum of Natural History 66: 116–120.
OpenUrl

[88] ↵
Mead J, Bell CJ. 2001. Pliocene amphibians and reptiles from Clark County, Nevada. Bulletin of the Southern California Academy of Sciences 100: 1–11.
OpenUrl

[89] ↵
Mead JI, Hollenshead MG, Swift SL, Bell CJ, Baynes A. 2008. Pygopus (Squamata: Pygopodidae) from mid-Holocene cave deposits, Western and South Australia. Records of the Western Australian Museum 25: 87–93.
OpenUrl GeoRef

[90] ↵
Mead JI, J Arroyo Cabrales, Johnson E. 1999. Pleistocene Lizards (Reptilia: Squamata) from San Josecito Cave, Nuevo León, México. Copeia 1999: 163–173.
OpenUrl

[91] Mead JI, Roth EL, Van Devender TR, Steadman DW. 1984. The late Wisconsinan vertebrate fauna from Deadman Cave, southern Arizona. Transactions of the San Diego Society of Natural History 20: 247–276.
OpenUrl

[92] ↵
Meszoely CAM. 1970. North American fossil anguid lizards. Bulletin of the Museum of Comparative Zoology at Harvard College. 139: 87–149.
OpenUrl

[93] ↵
Meyers JJ, Herrel A, Nishikawa KC. 2006. Morphological correlates of ant eating in horned lizards (Phrynosoma). Biological Journal of the Linnean Society 89: 13–24.
OpenUrl

[94] ↵
Montanucci RR. 1987. A phylogenetic study of the horned lizards, genus Phrynosoma, based on skeletal and external morphology. Contributions in science 390: 1–36.
OpenUrl

[95] Nash DF. A comparative study of the head and thoracic osteology and myology of the skinks, Eumeces gilberti Van Denburgh and Eumeces skiltonianus (Baird and Girard). Unpublished thesis, Brigham Young University.

[96] ↵
Norell MA. 1989. Late Cenozoic lizards of the Anza Borrego Desert, California. Natural History Museum of Los Angeles County Contributions in Science 414: 1–31.
OpenUrl

[97] ↵
Norris KS, Lowe CH. 1951. A study of the osteology and musculature of Phrynosoma m’callii pertinent to its systematic status. Bulletin of the Chicago Academy of Sciences 9: 117–125.
OpenUrl

[98] ↵
Nydam RL, Eaton JG, Sankey J. 2007. NEW TAXA OF TRANSVERSELY-TOOTHED LIZARDS (SQUAMATA: SCINCOMORPHA) AND NEW INFORMATION ON THE EVOLUTIONARY HISTORY OF “TEIIDS”. Journal of Paleontology 81: 538–549.
OpenUrl Abstract/FREE Full Text

[99] ↵
de Oca ANM, Arenas-Moreno D, Beltrán-Sánchez E, Leaché AD. 2014. A New Species of Horned Lizard (Genus Phrynosoma) from Guerrero, México, with an Updated Multilocus Phylogeny. Herpetologica 70: 241–257.
OpenUrl CrossRef

[100] ↵
Oelrich TM. 1956. The Anatomy of the Head of Ctenosaura pectinata (Iguanidae). Miscellaneous Publications Museum Of Zoology, University Of Michigan 94: 1–122.
OpenUrl

[101] ↵
Paluh DJ, Bauer AM. 2017. Comparative skull anatomy of terrestrial and crevice-dwelling Trachylepis skinks (Squamata: Scincidae) with a survey of resources in scincid cranial osteology. PLOS ONE 12: e0184414.
OpenUrl CrossRef

[102] ↵
Parmley D. 1988. Middle Holocene Herpetofauna of Klein Cave, Kerr County, Texas. The Southwestern Naturalist 33: 378–382.
OpenUrl GeoRef

[103] ↵
Parmley D, Bahn JR. 2012. LATE PLEISTOCENE LIZARDS FROM FOWLKES CAVE, CULBERSON COUNTY, TEXAS. The Southwestern Naturalist 57: 435–441.
OpenUrl

[104] ↵
Powell GL, Russell AP, Jamniczky HA, Hallgrímsson B. 2017. Shape Variation in the Dermatocranium of the Greater Short-Horned Lizard Phrynosoma hernandesi (Reptilia: Squamata: Phrynosomatidae). Evolutionary Biology 44: 240–260.
OpenUrl

[105] ↵
Pregill GK. 1981. Late Pleistocene herpetofaunas from Puerto Rico. Miscellaneous publication - University of Kansas, Museum of Natural History 71: 1–72.
OpenUrl

[106] ↵
Pregill GK. 1988. Late Holocene fossil vertebrates from Burma Quarry, Antigua, Lesser Antilles. Smithsonian Contributions to Zoology 463: 1–27.
OpenUrl

[107] ↵
Pregill GK. 1992. Systematics of the West Indian lizard genus Leiocephalus (Squamata: Iguania: Tropiduridae). Miscellaneous publication - University of Kansas, Museum of Natural History 84: 1–69.
OpenUrl

[108] ↵
Presch W. 1969. Evolutionary Osteology and Relationships of the Horned Lizard Genus Phrynosoma (Family Iguanidae). Copeia 1969: 250–275.
OpenUrl

[109] ↵
de Queiroz K. 1987. Phylogenetic Systematics of iguanine lizards. University of California Publications in Zoology 118: xii + 1–203.
OpenUrl

[110] ↵
Ramm T, Thorn KM, A. Hipsley C, Müller J, Hocknull S, Melville J. 2021. Herpetofaunal diversity changes with climate: evidence from the Quaternary of McEachern’s Deathtrap Cave, southeastern Australia. Journal of Vertebrate Paleontology 41: e2009844.
OpenUrl

[111] ↵
Reed FA, Kontanis EJ, Kennedy KAR, Aquadro CF. 2003. Brief communication: Ancient DNA prospects from Sri Lankan highland dry caves support an emerging global pattern. American Journal of Physical Anthropology 121: 112–116.
OpenUrl CrossRef PubMed Web of Science

[112] ↵
Rieppel Olivier. 1980. The phylogeny of anguinomorph lizards. Basel, Boston: Birkhäuser Verlag.

[113] ↵
Roscito JG, Rodrigues MT. 2010. Comparative cranial osteology of fossorial lizards from the tribe gymnophthalmini (Squamata, Gymnophthalmidae). Journal of Morphology 271: 1352– 1365.
OpenUrl PubMed

[114] ↵
Roth EL. 1972. Late Pleistocene Mammals From Klein Cave, Kerr County, Texas. The Texas Journal of Science 24: 75–84.
OpenUrl

[115] ↵
Savage JM. 1963. Studies on the lizard family Xantusiidae. IV. The genera. Contributions in Science 71: 1–38.
OpenUrl

[116] ↵
Scarpetta S. 2018. The earliest known occurrence of Elgaria (Squamata: Anguidae) and a minimum age for crown Gerrhonotinae: Fossils from the Split Rock Formation, Wyoming, USA. Palaeontologicia Electronica 21.1.1FC: 1–9.
OpenUrl

[117] ↵
Scarpetta SG. 2019. The first known fossil Uma: ecological evolution and the origins of North American fringe-toed lizards. BMC Evolutionary Biology 19(178): 1–22.
OpenUrl CrossRef

[118] ↵
Scarpetta SG. 2020. Unusual lizard fossil from the Miocene of Nebraska and a minimum age for cnemidophorine teiids. Royal Society Open Science 7(200317): 1–12.
OpenUrl

[119] ↵
Scarpetta SG. 2021. Iguanian lizards from the Split Rock Formation, Wyoming: exploring the modernization of the North American lizard fauna. Journal of Systematic Palaeontology 19: 221–251.
OpenUrl

[120] ↵
Scarpetta SG, Ledesma DT, Bell CJ. 2021. A new extinct species of alligator lizard (Squamata: Elgaria) and an expanded perspective on the osteology and phylogeny of Gerrhonotinae. BMC Ecology and Evolution 21(184): 1–58.
OpenUrl CrossRef

[121] ↵
Seersholm FV, Werndly DJ, Grealy A, Johnson T, Keenan Early EM, Lundelius EL, Winsborough B, Farr GE, Toomey R, Hansen AJ, Shapiro B, Waters MR, McDonald G, Linderholm A, Stafford TW, Bunce M. 2020. Rapid range shifts and megafaunal extinctions associated with late Pleistocene climate change. Nature Communications 11(2770): 1–10.
OpenUrl

[122] ↵
Smith KT. 2006. A diverse new assemblage of Late Eocene squamates (Reptilia) from the Chadron Formation of North Dakota. Palaeontologicia Electronica 9(2;5A): 1–44.
OpenUrl

[123] ↵
Smith KT. 2009a. A new lizard assemblage from the earliest Eocene (Zone Wa0) of the bighorn basin, Wyoming, USA: Biogeography during the warmest interval of the Cenozoic. Journal of Systematic Palaeontology 7: 299–358.
OpenUrl

[124] ↵
Smith KT. 2009b. Eocene Lizards of the Clade Geiseltaliellus from Messel and Geiseltal, Germany, and the Early Radiation of Iguanidae (Reptilia: Squamata). Bulletin of the Peabody Museum of Natural History 50: 219–306.
OpenUrl

[125] ↵
Smith KT. 2011. The Evolution of Mid-Latitude Faunas During the Eocene: Late Eocene Lizards of the Medicine Pole Hills Reconsidered. Bulletin of the Peabody Museum of Natural History 52: 3–105.
OpenUrl

[126] ↵
Gower DG,
Zaher H
Smith KT, Georgalis GL. 2022. The Diversity and Distribution of Palaeogene Snakes. In: Gower DG, Zaher H, eds. The Origin and Early Evolutionary History of Snakes. Cambridge, United Kingdon: Cambridge University Press, 55–84.

[127] Gower DG,

[128] Zaher H

[129] ↵
Smith FA, Tomé CP, Elliott Smith EA, Lyons SK, Newsome SD, Stafford TW. 2016. Unraveling the consequences of the terminal Pleistocene megafauna extinction on mammal community assembly. Ecography 39: 223–239.
OpenUrl CrossRef

[130] ↵
Syromyatnikova E, Aranda E. 2022. A record of galliwasp (Diploglossidae: Diploglossus) from the Pleistocene of Cuba. Historical Biology: 1–5. doi:10.1080/08912963.2022.2077108.
OpenUrl CrossRef

[131] ↵
Tarazona OA, Fabrezi M, Ramírez-Pinilla MP. 2008. Cranial morphology of Bachia bicolor (Squamata: Gymnophthalmidae) and its postnatal development. Zoological Journal of the Linnean Society 152: 775–792.
OpenUrl

[132] ↵
Taylor EH. 1940. Palatal sesamoid bones and palatal teeth in Cnemidophorus, with notes on these teeth in other saurian genera. Proceedings of the Biological Society of Washington 53: 119–123.
OpenUrl

[133] ↵
Tedesco ME, Krause L, Alvarez BB. 1999. Descripción del sincraneo de Ameiva ameiva (Linnaeus) (Squamata, Teiidae). Revista Brasileira de Zoologia 16: 1025–1044.
OpenUrl

[134] ↵
Toerien MJ. 1950. The cranial morphology of the Californian lizard-Anniella pulchra Gray. South African Journal of Science 46: 321–342.
OpenUrl

[135] ↵
Tollis M, Boissinot S. 2014. Genetic variation in the green anole lizard (Anolis carolinensis) reveals island refugia and a fragmented Florida during the quaternary. Genetica 142: 59–72.
OpenUrl CrossRef PubMed Web of Science

[136] ↵
Toomey RS. 1993. Late Pleistocene and Holocene faunal and environmental changes at Hall’s Cave, Kerr County, Texas. Unpublished thesis, The University of Texas at Austin.

[137] Torres-Carvajal O. 2003. Cranial Osteology of the Andean Lizard Stenocercus guentheri (Squamata: Tropiduridae) and Its Postembryonic Development. Journal of Morphology 255: 94– 113.
OpenUrl PubMed

[138] ↵
Townsend VR, Akin JA, Felgenhauer BE, Dauphine J, Kidder SA. 1999. Dentition of the Ground Skink, Scincella lateralis (Sauria, Scincidae). Copeia 1999: 783–788.
OpenUrl

[139] ↵
Vasilyan D, Bukhsianidze M. 2020. The fossil record of the genus Varanus from the Southern Caucasus (Armenia, Georgia). PeerJ 8: e8322.
OpenUrl

[140] ↵
Villa A, Delfino M. 2019. A comparative atlas of the skull osteology of European lizards (Reptilia: Squamata). Zoological Journal of the Linnean Society 187: 829–928.
OpenUrl

[141] ↵
Waters MR, Keene JL, Prewitt ER, Everett ME, Laughlin T, Stafford TW. 2021. Late Quaternary geology, archaeology, and geoarchaeology of Hall’s Cave, Texas. Quaternary Science Reviews 274: 107276.
OpenUrl

[142] Yánez-Muñoz MH, Torres-Carvajal O, Reyes-Puig JP, Urgiles-Merchán MA, Koch C. 2021. A new and very spiny lizard (Gymnophthalmidae: Echinosaura) from the Andes in northwestern Ecuador. PeerJ 9: e12523.
OpenUrl