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Taxonomy of the proterosuchid archosauriforms ( D iapsida: A rchosauromorpha) from the earliest T riassic of S outh A frica, and implications for the early archosauriform radiation
Author(s) -
Ezcurra Martín D.,
Butler Richard J.
Publication year - 2015
Publication title -
palaeontology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.69
H-Index - 63
eISSN - 1475-4983
pISSN - 0031-0239
DOI - 10.1111/pala.12130
Subject(s) - taxonomy (biology) , taxon , holotype , zoology , biology , paleontology
Proterosuchidae is one of the first clades of A rchosauriformes (archosaurs and closely related species) to appear in the fossil record, with the richest sample of the group coming from the L ystrosaurus A ssemblage Z one (earliest T riassic) of S outh A frica. Four nominal proterosuchid species were described from S outh A frica during the twentieth century ( P roterosuchus fergusi , C hasmatosaurus vanhoepeni , C hasmatosaurus alexanderi and E laphrosuchus rubidgei ), but interpretations of their taxonomy have been widely disparate. The most recent taxonomic revision concluded that P . fergusi is the only valid species and that the other nominal species are junior subjective synonyms of this taxon. This proposal was based on the interpretation that anatomical differences between the nominal species could be explained as a result of ontogenetic changes and/or post‐mortem deformation. The recent discoveries of multiple new S outh A frican proterosuchid specimens provide an impetus to revisit their taxonomy. Based upon a comprehensive re‐examination of all known specimens, as well as examination of other proterosuchid taxa in collections worldwide, we conclude that the holotype of P roterosuchus fergusi is undiagnostic. As a result, we propose a neotype ( RC 846) for the species. ‘ C hasmatosaurus vanhoepeni ’ and ‘ E laphrosuchus rubidgei ’ are considered subjective junior synonyms of P . fergusi . ‘ C hasmatosaurus ’ alexanderi is considered a valid species, for which we propose the new combination P . alexanderi comb. nov. A third species, P . goweri sp. nov., is erected on the basis of a single specimen ( NMQR 880). All three species recognized here are taxonomically distinct from a previously described archosauriform maxilla from the lower L ystrosaurus AZ . As a result, we recognize a minimum of four archosauriform species following the P ermo‐ T riassic mass extinction in S outh A frica. Our results suggest a greater species richness of earliest T riassic archosauriforms than previously appreciated, but that archosauriform morphological disparity remained low and did not expand until the late E arly T riassic – early M id‐ T riassic.