A Reappraisal Of Coletta Seca, A Basal Procolophonoid Reptile From The Lower Triassic Of South Africa

Abstract

The skeletal structure of Coletta seca, a small procolophonoid reptile from the Lower Triassic Lystrosaurus Assemblage Zone of South Africa, is reconsidered in light of descriptions of other procolophonoids. The presence of a single row of relatively large, fang–like vomerine teeth, identified originally as the single autapomorphy of this taxon, is reinterpreted as two rows of parachoanal vomerine teeth that are similar in organization to those of coeval procolophonids from Russia. Coletta is distinguished from other procolophonoids by a complex tongue–and–groove suture between the anterolateral margin of the parietal and the posterolateral edge of the postfrontal, and by a transversely broad interpterygoid vacuity. The postfrontal in Coletta retains contact with the postorbital, as in basal taxa such as Owenetta, but it is restricted to the orbital margin, as in Procolophon and all other procolophonids. A phylogenetic analysis identifies Coletta as the sister taxon of the clade Procolophonidae. This phylogenetic position suggests that Procolophonoidea originated and diversified initially in Gondwana during the Permian, prior to Procolophonidae achieving a cosmopolitan distribution in the succeeding Triassic.