A new species of Elkanemys (Pleurodira: Pelomedusoides) from the Portezuelo Formation (Turonian–Coniacian) of Patagonia, Argentina

Abstract

We describe Elkanemys caelestis sp. nov., a pelomedusoid turtle, based on two specimens from the Baal locality, Portezuelo Formation (Turonian-Coniacian), situated on the northern shore of Barreales Lake, Neuquén Province, Argentina. Specimens MUC-Pv 2218 and MUC-Pv 2219 represent two individuals, preserving both the carapace and plastron articulated by the bridge, showing characteristics of Pelomedusoides within Pleurodira, such as absence of a cervical scute, lateral rounded mesoplastra and a wide posterior plastral lobe. MUC-Pv 2219 also preserves the skull which exhibits characteristics typical of Pelomedusoides such as the presence of a quadratojugal bone and the absence of nasal bones. The carapace of MUC-Pv 2219 exhibits an anomaly of supernumerary peripheral bones and marginal scutes. Furthermore, MUC-Pv 2219 presents a unique indeterminate sub-triangular bone element ventral to the dentary, which is not described in other Cretaceous pleurodires. Both specimens demonstrate shared features, including hexagonal first neurals with short posterolateral sides and quadrangular second neurals, reinforcing their placement within the genus Elkanemys. Our phylogenetic analysis recovers Elkanemys as a member of Podocnemidoidae, exhibiting close affinities with Bauru Basin species.