Anatomy and relationships of Elliotsmithia longiceps Broom, a small synapsid (Eupelycosauria: Varanopseidae) from the late Permian of South Africa

Abstract

ABSTRACT Elliotsmithia longiceps Broom, 1937 is a varanopseid synapsid from the middle part of the Tapinocephalus Assemblage Zone (Late Permian) of the Abrahamskraal Formation (Beaufort Group), South Africa. Its placement within this basal eupelycosaur clade is supported by the presence of the following features: strongly recurved, mediolaterally flattened marginal dentition, a tall and posteroventrally enlarged temporal fenestra, a narrow lower temporal bar formed by the jugal and quadratojugal with only a small contribution from the maxilla, a long medial process of the parietal that extends far anteriorly over the orbital region, and distinctive ornamentation on three circumorbital bones. Analysis of varanopseid phylogenetic relationships indicates that Elliotsmithia is a sister taxon to the clade formed by the medium-sized North American varanopseids Varanops, Aerosaurus, and Varanodon. Elliotsmithia is unique among Paleozoic synapsids in showing evidence of supravertebral armor. Elliotsmithia is important biogeo-graphically because it is the only known Permo-Carboniferous synapsid from the Southern Hemisphere in an assemblage dominated both numerically and taxonomically by therapsids. It demonstrates that Permo-Carboniferous synapsids were not excluded ecologically by therapsids and restricted to equatorial regions during the Late Permian.