L.S. Filippi1, R.D. Juarez Valieri2 y C.A. Garrido3

We report a new abelisaurid theropod specimen, which represent the most complete abelisaurid theropod skeleton yet reported from the Bajo de La Carpa Formation. It comes from the La Invernada area, located 50 kilometers south from Rincón de los Sauces, Neuquén Province. The partially excavated material is well preserved and display scarce signs of deformation. The pieces recovered comprises a partial skull with complete basicranium, both frontals, postorbitals and squamosals, four cervical vertebrae including atlas, eight dorsals and eigth caudals, cervical and dorsal ribs, an haemal arch, and indeterminate pieces. The frontals are flat, opposite to the condition present in Abelisaurus, Aucasaurus and Carnotaurus. The postorbitals present slightly convex and ornamented dorsal margins, in contrast to Ekrixinatosaurus and Skorpiovenator. The jugal process of the postorbitals is anteriorly recurved thus enclosing the orbit, a character proposed as autapomorphic of Brachyrostra. The cervical vertebrae show anterior processes on the epipophysis and reduced neural spines as in Carnotaurus. The anterior and middle caudal vertebrae are tipical of derived abelisaurids, with strong centrodiapophyseal laminae and with laterodorsally projected and distally expanded transverse processes. Is evident the presence of hyposphene-hypantrum in the anterior caudals as in Aucasaurus and Carnotaurus, but it appear absent in the preserved middle caudals, similar to Ilokelesia. This new specimen is relevant both anatomically and phylogenetically, contributing to the knowledge of the abelisaurid theropods, and increasing the diversity of the Cretaceous vertebrates from the Bajo de la Carpa Formation.

1 Museo Municipal Argentino Urquiza. Jujuy y Chaco s/n, 8319, Rincón de los Sauces, Neuquén, Argentina.

2 Secretaría de Cultura de la Provincia de Río Negro, 8332 General Roca, Río Negro, Argentina.

3  Museo Provincial de Ciencias Naturales Prof. Dr. Juan Olsacher, Dirección Provincial de Minería. Etcheluz y Ejército Argentino, 8340, Zapala, Neuquén, Argentina.
 
Resumenes XXVIII Jornadas Argentinas de Paleontología de Vertebrados, Zapala-Chocón, Neuquén, Argentina. 21 al 23 de Mayo del 2014.