A predation attempt in a Late Cretaceous pleurodire turtle from Patagonia

Abstract In the present contribution, we report the evidence of a predation attempt against a semi-aquatic pleurodire turtle who survived the attack. The almost complete specimen of this adult turtle, the holotype of Rionegrochelys caldieroi, was found in the Upper Cretaceous Plottier Formation, El Anfiteatro area, Rio Negro province, Patagonia. The shell displays two distinct but synchronously produced trace fossils in the anterior right portion of the plastron. One of the trace fossils is semicircular and indicates where the bone has been broken during the attack, as a consequence of a bite. The other one reflects the predator’s teeth morphology, and suggests a crocodyliform as the best candidate. Computed tomography analysis reveals regenerated tissue associated with both trace fossils, indicating healing of the wound. No vital organ was seriously injured during the attack, and the turtle survived, lacking a fragment of the shell. Taking into account the evidence in the fossil record, the unambiguous predator-prey relationship between crocodyliforms and turtles is present from at least the Late Jurassic, and the Rionegrochelys caldieroi holotype and their trace fossils is a new evidence of this interaction.