RT Journal Article
SR Electronic
T1 Tomographic data of ‘acanthodian’ oral structures and a review of dental diversity in early chondrichthyans
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2020.07.08.193839
DO 10.1101/2020.07.08.193839
A1 Dearden, Richard P.
A1 Giles, Sam
YR 2021
UL http://biorxiv.org/content/early/2021/05/07/2020.07.08.193839.abstract
AB The teeth of sharks famously form a series of parallel, continuously replacing files borne directly on the jaw cartilages. In contrast, bony fishes possess site-specific shedding dentition borne primarily on dermal plates. Understanding how these disparate systems evolved is challenging, not least because of poorly understood relationships amongst early chondrichthyans and the profusion of morphologically and terminologically diverse bones, cartilages, splints and whorls that they possess. Here we use tomographic methods to investigate mandibular structures in several early branching ‘acanthodian’-grade stem-chondrichthyans. We characterise the dentigerous jaw bones of disparate genera of ischnacanthids as growing bones with non-shedding dentition. Mandibular splints, which support the ventro-lateral edge of the Meckel’s cartilage in some acanthodians, are formed from dermal bone and may be an acanthodid synapomorphy. We strengthen the case for Acanthodopsis as an acanthodid deeply nested within an edentulous radiation and show that its teeth are borne directly on the mandibular cartilage, unexpectedly representing an independent origin of teeth. Poor resolution of relationships amongst ‘acanthodians’ represents a major barrier to understanding the evolution and homology of teeth and associated oral structures.Competing Interest StatementThe authors have declared no competing interest.