Abstract

Sinaspideretes wimani Young & Chow, 1953 was based on a single shell from the Jurassic red beds of the Sichuan Basin. Originally referred to Trionychidae but later tentatively assigned to Carettochelyidae, it was long thought to be the oldest representative of those families. The re-examination of the carapace and further preparation of the plastron of the holotype of S. wimani revealed a number of important characters which clearly exclude this taxon from both Trionychidae and Carettochelyidae, but unite it with the primitive trionychoid Yehguia tatsuensis (Ye, 1963). S. wimani is therefore considered as the basalmost member of Trionychoidae. Our study adds to the evidence from the fossil record for the antiquity of Trionychoidae, thus is in agreement with the early split of Trionychia (Trionychidae and Carettochelyidae) among the crown Testudines suggested by the molecular phylogeny of turtles.

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