RT Journal Article
SR Electronic
T1 The oldest peracarid crustacean reveals a Late Devonian freshwater colonisation by isopod relatives
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2021.04.25.441336
DO 10.1101/2021.04.25.441336
A1 N. Robin
A1 P. Gueriau
A1 J. Luque
A1 D. Jarvis
A1 A.C. Daley
A1 R. Vonk
YR 2021
UL http://biorxiv.org/content/early/2021/04/27/2021.04.25.441336.abstract
AB Peracarida (e.g., woodlice & side-swimmers) are, together with their sister-group Eucarida (e.g. krill & decapods), the most speciose group of modern crustaceans, suggested to have appeared as early as the Ordovician. While eucarids incursion onto land consists of mainly freshwater and littoral grounds, some peracarids have evolved fully terrestrial ground-crawling ecologies, inhabiting even our gardens in temperate regions (e.g. pillbugs and sowbugs). Their fossil record extends back to the Carboniferous and consists mainly of marine occurrences. Here, we provide a complete re-analysis of a fossil arthropod – Oxyuropoda – reported in 1908 from the Late Devonian floodplains of Ireland, and left with unresolved systematic affinities despite a century of attempts at identification. Known from a single specimen preserved in two-dimensions, we analysed its anatomy using digital microscopy and multispectral macro-imaging to enhance contrast of morphological structures. The new anatomical characters and completeness of Oxyuropoda, together with a phylogenetic analysis with representatives of all major Eumalacostraca groups, indicate that Oxyuropoda is a crown-peracarid, part of a clade including amphipods and isopods. As such, Oxyuropoda is the oldest known Peracarida, and provides evidence that derived peracarids had an incursion into freshwater and terrestrial environments as early as the Famennian, more than 360 million years ago.Competing Interest StatementThe authors have declared no competing interest.