Pterosaur remains (Archosauria, Ornithodira) from the early Late Cretaceous of La Buitrera, Río Negro, Argentina
The finely stratified reddish sandy levels of the La Buitrera facies (Candeleros Formation, Neuquén basin) has provided a rich diversity in small to medium-sized tetrapods, including sphenodontians, limbed snakes, araripesuchid crocodyliforms, theropod and sauropod dinosaurs, mammals, and dipnoans. Here we describe pterosaurian bones yielded at La Buitrera locality, from the uppermost section of Candeleros Formation. The new materials, from two specimens, are composed by: the distal portion of a right ulna (MPCN-PV 101), and a partially preserved right wing represented by an almost complete ulna (fused to the radius) articulated with proximal and distal syncarpals, metacarpal IV and the proximal part of the first wing phalanx (MPCN-PV 102). MPCN-PV 101 can be identified as a pterosaur from the presence of extremely thin-walled bone, a convex tuberculum, a concave fovea carpalis and the obliquely angled dorsal condyle on the distal articular view. The L-shaped distal outline allows its recognition as belonging to the Tapejaroidea. The presence of tapejaroid in the Limayan assemblage extends the knowledge of pterosaurs representation in the Neuquén Group with the reported azdharchids from the Neuquenian assemblage. The second specimen (MPCN-PV 102) shows a peculiar combination of features including the syncarpal shape, a high ulna (preserved)/IV metacarpal and WF1 (preserved)/Mc IV ratios that allows its recognition as a basal pterosaur. The complete fusion of radius-ulna, proximal and distal carpals and the extensor tendon process imply an adult state for the specimen. The presence of both tapejaroids and basal pterosaurs in the Neuquén Group suggests a high pterosaur diversity of Upper Cretaceous continental assemblages.