Original paper

Sutures of the shell of the Late Cretaceous-Paleocene baenid turtle Denazinemys

Lichtig, Asher J.; Lucas, Spencer G.

Abstract

The sutures of the Late Cretaceous-Paleocene turtle Denazinemys are described in detail and sexual dimorphism recognized based on historical specimens and newly studied, unfused shells. The carapace is remarkable in the possession of an unfused paired nuchal. While it has been observed in turtle embryology that this bone has two ossification centers, this is the first adult turtle known to show this morphology. Furthermore, the pustules on the surface of the carapace of Denazinemys do not align with the sutures, crossing them with no change. Conversely, the pustules are clearly interrupted by the sulci. Histological examination reveals that the pustules on the dorsal surface are composed of an expanded external cortex with no noticeable expansion of the cancellous bone layer. The plastron of Denazinemys is particularly similar to Boremys in the intersection of the gular-humeral sulcus at the widest point of the entoplastron. Overall, the sutures are consistent with what would be expected from the proposed sister group relationship ofDenazinemys with Boremys based on sulci and skull anatomy.

Keywords

paleoceneosteologycretaceousdenazinemysturtles