New pterosaur remains (Archosauria, Ornithodira) from the Late Cretaceous of Argentina and an evaluation of the Late Cretaceous South American record.

APESTEGUÍA, S., ŐSI, A., HALUZA, A.

München, Germany

Congreso; Wellnhofer Pterosaur Meeting; 2007

Bayerische Staatssammlung für Paläontologie und Geologie

Pterosaur assemblages of South America are relatively well-known for the Early Cretaceous coastal strata of the Santana Formation at Araripe and the lacustrine environments of the Lagarcito Formation at Sierra de las Quijadas, San Luis, Argentina. However, Upper Cretaceous pterosaurs of South America are very poorly known and any piece of information is relevant to contribute to its understanding. A recent exploration to rocks of the Upper Cretaceous of the Bajo de la Carpa Formation (Late Santonian-Early Campanian) at La Bonita locality, Río Negro Province, Argentina, allowed recognizing the presence of a phalanx I of the manual digit IV of a large-sized pterosaur (MPCN-PV 103). The extreme slenderness of the bone and a maximum length of about 40 cm (estimated total wing span about 4 metres), make its assignation undoubtable to a group of large pterosaurs, coherent with the already noticed presence of Azhdarchidae for the Portezuelo Formation. On the other side, the Candeleros Formation has recently provided pterosaurian bones at “La Buitrera” locality. The material consists of two specimens, a distal portion of a right ulna (MPCN-PV 101) considered as belonging to the Tapejaroidea, and a partially preserved right wing. The latter is 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). The syncarpal shape, a high ulna/IV metacarpal and WF1/Mc IV ratios exhibited by the specimen, as well as the adult stage evidenced by the complete fusion of radius-ulna, proximal and distal carpals and the extensor tendon process, is evident a very basal phylogenetic position within Pterosauria, completely unexpected for a Late Cretaceous material. The presence of both tapejaroids and basal pterosaurs in the Limayan assemblage of the Neuquén Group extends the knowledge of pterosaur representation; up to know formed by the reported azdharchids from the Portezuelo Formation (Neuquenian assemblage). This contributes to create a panorama of the poorly known pterosaur faunas and suggests important pterosaur diversity for the Upper Cretaceous completely continental assemblages of South America.