Dicraeosaurid Sauropod remains from the Mulichinco Formation (Valanginian, Lower Cretaceous), Neuquén Basin, Argentina.

WINDHOLZ, G.J.; CORIA, R.A.; BAIANO, M.A.; BELLARDINI, F.; PINO, D.

San Luis

Congreso; Reunión de comunicaciones de la Asociación Paleontológica Argentina (RCAPA, 2017).; 2018

Asociación Paleontológica Argentina

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 most abundantly represented form. The materials correspond to postcranial elements, representing different sections of the vertebral column. 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 completely absent neural spine. The specimen MLL-5 is a posterior dorsal vertebra with extremely long, slightly twisted and robust hemi-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 Cretaceous Amargasaurus, 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 resembles the condition of Amargasaurus. Also, like Suuwassea, the lateral sides of the centum of MLL-2 bear large pleurocoels, unlike from the condition of absence of pleurocoel in Amargasaurus and Brachytrachelopan. The new material yields additional evidence of a possible local radiation of South American Cretaceous dicraeosaurids. Although available material prevents specific taxonomic identification, additional more diagnostic specimens currently under lab-preparation will allow supporting the recognition of a likely new form