Data from: Taxonomy of the proterosuchid archosauriforms (Diapsida: Archosauromorpha) from the earliest Triassic of South Africa, and implications for the early archosauriform radiation

Proterosuchidae is one of the first clades of Archosauriformes (archosaurs
and closely related species) to appear in the fossil record, with the
richest sample of the group coming from the Lystrosaurus Assemblage Zone
(earliest Triassic) of South Africa. Four nominal proterosuchid species
were described from South Africa during the twentieth century
(Proterosuchus fergusi, Chasmatosaurus vanhoepeni, Chasmatosaurus
alexanderi and Elaphrosuchus 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 South African 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 Proterosuchus
fergusi is undiagnostic. As a result, we propose a neotype (RC 846) for
the species. ‘Chasmatosaurus vanhoepeni’ and ‘Elaphrosuchus rubidgei’ are
considered subjective junior synonyms of P. fergusi. ‘Chasmatosaurus’
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 Lystrosaurus AZ. As a result, we
recognize a minimum of four archosauriform species following the
Permo-Triassic mass extinction in South Africa. Our results suggest a
greater species richness of earliest Triassic archosauriforms than
previously appreciated, but that archosauriform morphological disparity
remained low and did not expand until the late Early Triassic – early
Mid-Triassic.