THE SAUROPOD FAUNA OF THE BAJADA COLORADA FORMATION (BERRIASIAN?VALANGINIAN), NEUQUÉN PROVINCE, ARGENTINA

PABLO A. GALLINA; SEBASTIÁN APESTEGUÍA; ALEJANDRO HALUZA; JUAN IGNACIO CANALE; ALEJANDRO OTERO

Zapala y El Chocón

Jornada; XXVIII Jornadas Argentinas de Paleontologia de Vertebrados; 2014

museo juan olsacher , museo bachmann y fundacion Azara

The terrestrial tetrapod record of the lowermost Cretaceous (pre-Barremian) of South America is quite scarce, biased both by a reduced area of outcrops (restricted to southeastern Neuquén Basin) and a lack of systematic exploration on it. Successive fieldworks carried out since 2010 in Bajada Colorada locality, near Picún Leufú town, Neuquén, Argentina, allowed the recognition of a rich dinosaur fauna that includes sauropod and theropod representatives. The sauropods are well-represented by abundant skeletal remains of two specimens: a diplodocid and a dicraeosaurid, as well as several teeth. On one hand, the diplodocid remains (MMCH-Pv 63-1/8), which include three cervical, one dorsal and four caudal vertebrae, represent the first Diplodocidae in South America, and the youngest record of the clade anywhere. On the other hand, the dicraeosaurid specimen includes not only partially articulated vertebral elements but a slightly disarticulated skull. The latter is composed of the skull roof and braincase, left postorbital, left squamosal, left jugal, left quadratojugal, the edentulous part of the left maxilla and the nearly complete lower jaw with more than twenty teeth in position. All these new records will substantially contribute to a better understanding of the early evolution and diversification of the dinosaur faunas, providing for the first time a link between the Jurassic fauna of Chubut Province and the quite well-known post-Barremian faunal assemblages from southern continents. In addition, these new findings augment the list of sauropod clades in southern South America, thus turning this area into an extremely rich portrait of sauropod evolution.