219 Paleontology, Diversity, Extinction, Origination (Posters)

Tuesday, 21 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Side-Necked Turtles (Testudines, Pelomedusoides) From the Lares Limestone: The First Report of Preserved Keratin From Puerto Rico?

Paper number: 219-10
Program: Technical Sessions
Time: 10:00 AM – 10:15 AM

Authors

Abstract

Pelomedusoides Cope, 1868 is a clade of turtles currently restricted to freshwater environments in South America and Africa but had a much wider geographic distribution during the Cretaceous and Cenozoic, including India, Europe, and North America. Pelomedusoid turtles are characterized by a series of synapomorphies, including the absence of a cervical scute. These turtles are divided into three subclades: Podocnemididae, Pelomedusidae, and Bothremydidae. Here we describe specimens from the upper Oligocene (26.5–24.7 Ma) Lares Limestone in northwestern Puerto Rico. The material includes an articulated plastron, disarticulated carapacial elements, and appendicular elements, but no cranial elements. We compare these fossils with published data from extant and fossil pelomedusoids. We refer the Lares material to Podocnemididae indet. as they lack diagnostic elements that would facilitate a more precise designation. Furthermore, the presence of neurals in the referred specimens is interesting given the possible lack of neural plates in the stereogenyin podocnemidid Bairdemys, a taxon with multiple species and widespread distribution in Neogene marine deposits across the Caribbean, including Puerto Rico. This suggests three possibilities: (1) that the Lares podocnemidid represents a distinct taxon; (2) that complete loss of neural plates is only observed in Neogene Bairdemys; or (3) that the lack of neural plates is a synapomorphy of Bairdemys venezuelensis. Additionally, one of the specimens (UPRMP-3234) has a thin film of light brown material that we interpret as having an organic keratinous origin, based on comparison with other published specimens. Future studies should focus on additional fieldwork in Oligocene-aged deposits in Puerto Rico to improve our understanding of its herpetofauna, and additional XRF tests will be performed to test for an organic origin for the film in UPRMP-3234.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412030

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