DICRAEOSAURID SAUROPOD REMAINS FROM THE MULICHINCO FORMATION (VALANGINIAN, LOWER CRETACEOUS), NEUQUÉN BASIN, ARGENTINA

WINDHOLZ, GUILLERMO; CORIA, RODOLFO; PINO, DIEGO; BELLARDINI, FLAVIO

San Luis

Otro; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2017

Asociación Paleontológica Argentina- Universidad Nacional de San Luis

Field works on terrestrial sediments of the Mulichinco Formation at Pilmatué locality, 9 km north from Las Lajas, Neuquén,permitted the collection of dinosaur remains from different taxa, of which the dicraeosaurid sauropods seem to be the mostabundantly represented form. The materials correspond to postcranial elements, representing different sections of the vertebralcolumn. A mid-cervical vertebra (MLL-4) bears a significantly reduced neural spine and, although broken at their bases,seems to have had a pair of dorsally projected hemi-spines. The specimen MLL-2 corresponds to a posterior cervical vertebra(communicated in previous meetings) and it shows the typical well-developed dicraeosaurid hemi-spines and a completelyabsent neural spine. The specimen MLL-5 is a posterior dorsal vertebra with extremely long, slightly twisted and robusthemi-spines. Up to now, the caudal section is represented by isolated distal vertebrae with amphycoelic centra (MLL-10).Dicraeosauridae includes the Jurassic Dicraeosaurus, Suuwassea, Brachytrachelopan and possibly Dyslocosaurus, and the CretaceousAmargasaurus, Amargatitanis and indeterminate remains from the partially synchronic Bajada Colorada Formation.Unlike Dicraeosaurus and Brachytrachelopan, the development of the presacral hemi-spines of the new material resemblesthe condition of Amargasaurus. Also, like Suuwassea, the lateral sides of the centum of MLL-2 bear large pleurocoels, unlikefrom the condition of absence of pleurocoel in Amargasaurus and Brachytrachelopan. The new material yields additional evidenceof a possible local radiation of South American Cretaceous dicraeosaurids. Although available material prevents specifictaxonomic identification, additional more diagnostic specimens currently under lab-preparation will allow supporting therecognition of a likely new form.