The last marine pelomedusoids (Testudines: Pleurodira): a new species of Bairdemys and the paleoecology of Stereogenyina

PeerJ. 2015 Jun 30;3:e1063. doi: 10.7717/peerj.1063. eCollection 2015.


The extinct Stereogenyina turtles form a relatively diverse Podocnemididae lineage, with twelve described and phylogenetically positioned species. They are characterized by a wide geographic and temporal range, from the Eocene of Africa to the Pleistocene of Southeast Asia, and a peculiar palate morphology, with a secondary palate that is unique among side-necked turtles. Here, we describe a new Stereogenyina species, based on an almost complete skull from the middle Miocene Capadare Formation, of Venezuela. A new phylogenetic analysis supports the assignment of the new species to the genus Bairdemys. Based on geometric morphometrics analyses, we related the development of the stereogenyin secondary palate with the acquisition of a durophagous diet. Based on a review of the sedimentary environments where their fossils are found, we also propose that stereogenyins were a marine radiation of podocnemidid turtles, as corroborated by previous studies of fossil eggs and limb morphology. These two inferences allowed us to hypothesize that stereogenyins occupied an ecological niche similar to that of the extant Carettini sea turtles, and that the rise of the latter group may be related to the Stereogenyina diversity fall in the end of the Miocene.

Keywords: Bairdemys; Durophagy; Marine pelomedusoides; Miocene; Paleoecology; Podocnemididae; Stereogenyina; Venezuela.

Grants and funding

This research was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) scholarships to GSF (2012/11604-1) and research funding to MCL (2014/03825-3), and by Venezuelan education university, science, and technology Ministry (MEUCT), research fundings IVIC-1096 and PEII2012-456 to ADR and AS. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.