New information on the cranial and vertebral anatomy of Buitreraptor gonzalezorum (Theropoda, Unenlagiinae) and preliminary comparisons with other South American unenlagiines

FEDERICO A. GIANECHINI; SEBASTIÁN APESTEGUÍA; PETER J. MAKOVICKY

San Luis

Jornada; XXV Jornadas Argentinas de Paleontología de Vertebrados; 2010

Within the framework of a doctoral thesis on the small theropods coming from the Cerro Policía area (Candeleros Formation, Río Negro Province), new information of Buitreraptor gonzalezorum Makovicky, Apesteguía and Agnolín 2005, is presented herein, including partial comparisons with other unenlagiines. Shared cranial characters between Buitreraptor and Austroraptor cabazai Novas, Pol, Canale, Porfiri and Calvo 2009, include: skull exceeding femoral length by 25%; low anterior process of maxilla; large maxillary fenestra not dorsally displaced; more than twenty maxillary and dentary teeth; fluted teeth without serrations and without basal constriction; groove on the dentary containing a row of nutrient foramina. Otherwise, Buitreraptor differs from Austroraptor in having a larger maxillary fenestra; elongated frontals with dorsal depressions; triangular postorbital; compressed teeth, with an 8-shaped basal section. Concerning vertebral features, Buitreraptor has a faint ventral keel on the axis (not comparable with other unenlagiines); elongated medial cervicals; epipophyses on all cervicals; carotid process on the latest cervicals; ventro-lateral ridges on the last cervical culminating posteriorly as small tubers; neural spines of the dorsals without distal spine tables (this latter feature invalidates a proposed synapomorphy for Unenlagiinae). Additionally, while pleurocoels are restricted to anterior dorsals in Buitreraptor (and probably in Austroraptor), in Unenlagia comahuensis Novas and Puerta 1997, they are in anteriorand posterior dorsals; and the foramina that pierces the base of the neural spines in the latter are absent in the two former. This analysis increases the knowledge of the anatomy of Buitreraptor and shows a high internal variability among unenlagiines.