Phrynops Wagler, 1830 (Testudines, Chelidae) in the Late Miocene of Palo Pintado Formation, Salta Province, Argentina, with comments on taxonomy and paleoenvironmental settings

Abstract

Pleurodiran chelid turtles are represented from the Late Miocene in northeastern and northwestern Argentina by species assigned to Phrynops sensu stricto = Phrynops geoffroanus complex. In the northeastern region, these turtles include the extinct species Phrynops paranensis (Wieland, 1923) from the Ituzaingo Formation, Entre Ríos Province. On the other hand, from the Late Miocene of northwestern Argentina, Phrynops specimens include unnamed species from the El Morterito (Cajon Valley, Catamarca Province) and Andalhualá (Tiopunco, Santa María Valley, Tucumán Province) formations. In this contribution, a new and relatively complete specimen assigned to Phrynops sensu stricto (Phrynops sp.) from the upper levels of the Palo Pintado Formation exposed in Quebrada Salta (Salta Province) is described and compared. The particular morphology of the specimen analyzed, different both from Phrynops paranensis, the only extinct species recognized for the genus, as well as from the current species of the genus, suggests the presence of at least two taxa in the Late Miocene of Argentina, one limited to the northeastern region (Phrynops paranensis) and another as yet unnamed from the northwestern region. Sedimentological analysis and fossil evidence analyzed for the sector strongly suggest the development of a tropical climate during the deposition of the Palo Pintado Formation. Considering that Phrynops sensu stricto spp. currently inhabiting freshwater lowlands in tropical to humid temperate climates, the presence of this aquatic species is consistent with the paleoenvironmental conditions previously interpreted for this unit.