Freshwater turtles (Testudines: Pleurodira) in the Upper Cretaceous of Chilean Patagonia

Abstract

We describe remains of freshwater turtles from the Upper Cretaceous of Chilean Patagonia. The fossils, which comprise isolated shell fragments and incomplete appendicular bones, were recovered from meandering fluvial deposits of the Dorotea Formation (upper Campanian–Danian), in the Río de Las Chinas Valley, Magallanes region. These remains represent the first records of Upper Cretaceous pan-chelid pleurodiran turtles in the Magallanes-Austral Basin. The shell fragments show a strong ornamentation of irregular polygons distributed over their entire external surface, and one of the peripheral plates is narrow and elongated. These features are consistent with traits described in Yaminuechelys, a chelid genus from the Upper Cretaceous and Paleogene of Argentinian Patagonia. In addition, the suprapygal plate presents sulci that mark the limits of the vertebral scute 5 and the marginal scutes 12 as in Yaminuechelys sulcipeculiaris. This finding represents the southernmost record of a species conferred to Yaminuechelys, extending the distribution of this genus to the Magallanes-Austral basin during the Campanian–Maastrichtian.