New species of the long-necked chelid Yaminuechelys from the Upper Cretaceous (Campanian–Maastrichtian) of Chubut, Argentina

Abstract

A new species of a long-necked chelid from the uppermost Cretaceous (Campanian–Maastrichtian) is presented in this contribution. Yaminuechelys sulcipeculiaris sp. nov. is found in outcrops of the La Colonia Formation in the northeast part of Chubut province, Argentina. This new species is mainly represented by carapacial, plastral, and postcranial remains (vertebrae and long bones). It was assigned to Yaminuechelys because it presents characters shared with the species Yaminuechelys gasparinii de la Fuente, Lapparent de Broin, and Manera de Bianco, 2001 and Yaminuechelys maior (Staesche, 1929). Those characters are a large shell with irregular polygons distributed on the external surface, the difference in length between the anterior and posterior peripheral bones, and the neural series separated from the suprapygal bones. Other characters, like the position of the sulcus between vertebral 5 and marginal 12 crossing the suprapygal and the location of the sulcus between the vertebral 5 and the marginal 11 crossing the costal 8 and suprapygal, suggest it is a new species. According to the phylogenetic analysis performed, the new species forms a monophyletic group together with Y. maior, and Y. gasparinii. The survival of Yaminuechelys to the K/Pg extinction event is also discussed.