Occurrence of a Quaternary cheloniid sea turtle from the Southern Argentine Pampas

The fossil record of marine turtles from South America is scarce. In Argentina, these remains are largely restricted to pre-Pliocene strata, with no reliable reports of Quaternary material. Here, we describe a near-complete right humerus of a cheloniid sea turtle (Cheloniidae, Chelonioidea) from coastal deposits at Punta Médanos, south of Mar de Ajó in Buenos Aires Province, Argentina. Geological and correlative faunal evidence indicates a Late Pleistocene age, possibly around the Riss–Würm Interglacial (MIS 5e) interval. The humerus exhibits diagnostic character states consistent with the extant Green sea turtle, Chelonia mydas. This discovery represents the first Quaternary marine turtle occurrence from the southeastern Atlantic margin. Although C. mydas seasonally migrates along the Argentine coast, its distribution further south during the Late Pleistocene deposits is congruent with proposed warmer climatic conditions prevailing in the southern Atlantic earlier in the Quaternary.Mariano Mársico Fettolini* [marianomarsicofettolini@gmail.com], Laboratorio de Paleontología de Vertebrados, Centro de Investigación Científica y de Transferencia Tecnológica a La Producción (CONICET- Gob. de ER-UADER), España 149, E3105BWA Diamante, Entre Ríos, Argentina; Federico L. Agnolin [fedeagnolin@yahoo.com.ar], Laboratorio de Anatomía Comparada y Evolución de los Vertebrados (LACEV), Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (MACN-CONICET), Av. Ángel Gallardo 470, C1405DJR, Buenos Aires, Argentina; Fundación de Historia Natural “Félix de Azara”, Departamento de Ciencias Naturales y Antropología, Universidad Maimónides, Hidalgo 775, C1405BDB, Ciudad Autónoma de Buenos Aires, Argentina; Raul I. Vezzosi [vezzosiraul@gmail.com], Laboratorio de Paleontología de Vertebrados, Centro de Investigación Científica y de Transferencia Tecnológica a La Producción (CONICET- Gob. de ER-UADER), España 149, E3105BWA Diamante, Entre Ríos, Argentina; Facultad de Ciencia y Tecnología, Universidad Autónoma de Entre Ríos, Ruta Nacional N° 11 Km 10,5, E3100XAD Oro Verde, Entre Ríos, Argentina.