An Upper Miocene marine turtle from Panama that preserves osteocytes with potential DNA

Abstract

Lepidochelys is a genus of extant marine turtles that includes the critically endangered Kemp's Ridley turtle. The evolutionary history of this genus is poorly understood due to the lack of an undisputed fossil record for the group. Here we describe a partially preserved carapace from the Upper Miocene Chagres Formation of Panama, which represents the oldest fossil record of Lepidochelys. The specimen has rectangular, anteroposteriorly short pleural scutes, a characteristic shared with members of Lepidochelys. It is potentially closely related to L. olivacea because it shares a similar number of pleurals, but its precise taxonomic status remains uncertain. We discuss the ecological role that a marine turtle played in the paleoecosystem of the Chagres Formation. The new specimen exhibits exceptional preservation of bone sutures, sulci, sculpturing, and bone microstructure, including remains of blood vessels, collagen fibers, and osteocytes. This is the first time that a histochemical stain (DAPI) indicates preservation of a compound consistent with DNA in a fossil vertebrate outside Dinosauria. These data demonstrate the potential for DNA to persist in specimens that are both millions of years old and are from lower latitudes, which challenges traditional paradigms of biomolecular preservation.

Molecules of Lost Time

“…Ancient DNA discoveries keep coming from unexpected places. Thus, Edwin Cadena of the Universidad del Rosario in Bogotá, Colombia, and colleagues recently reported the discovery of a turtle carapace fragment on the coast of Panama, which not only brought important insights into the evolution of sea turtles at the time when North and South America merged, but also contained traces of DNA [6] .…”