Presence of Phrynops (Testudines, Chelidae) in the Late Miocene Palo Pintado Formation, Northwestern Argentina

LUNA, CARLOS ALBERTO; LANDA RAMÍREZ, ENZO; ZURITA, ALFREDO E.; GALLI, CLAUDIA I.; ROBLEDO, JUAN M.; BAEZ, JOHANA; FARREL, EZEQUIEL; ZAMUDIO, BELÉN; CANDELA, ADRIANA M.; CUADRELLI, FRANCISCO; ALONSO, RICARDO N.

La Rioja

Congreso; VII Simposio del Mioceno-Pleistoceno del Centro y Norte de Argentina; 2023

Asociación Paleontológica Argentina

The Palo Pintado Formation (ca. 10–5 Ma; Late Miocene) shows a wide diversity of fossil vertebrates including mainly mammals, turtles, and caimans. Although turtles are quite frequent in the fossil record of the formation, they have not been described in detail. The only previous record reported for this unit corresponds to an undetermined Chelidae from the Quebrada de Piscuyacu, near of Angastaco, Salta Province. In the present contribution we report from a cuspidal level of Palo Pintado Formation a part of the posterior region of the carapace (with five neurals, seven costals, suprapigal, and pigal) and plastron (hio, hipo, and xifoplastrón) of a turtle [CNS-V-038], which may have reached up to 32 cm in length, and whose characteristics allow us to refer it to the genus Phrynops Wagler, 1830. When compared to different genera of Chelidae recorded for the Neogene of South America (Acanthochelys, Mesoclemmys, Phrynops, and Hydromedusa), the carapace differs from Acanthochelys and Mesoclemmys in the presence of a continuous series of neural plates, from Hydromedusa in lacking upturned lateral margins, and presents, as in some extant and extinct species of Phrynops, peripheral plates of the posterior margin with ornamentation with fine grooves forming irregular polygons. This genus has been previously recorded from the Late Miocene of Catamarca, Tucumán, and Entre Ríos provinces in Argentina, and Uruguay. Phrynops currently inhabits freshwater lowlands in tropical to humid temperate climates. In consequence, the presence of this genus in the studied levels is consistent with environmental conditions previously interpreted for this unit.