The unusual dentition of Buitreraptor gonzalezorum (Theropoda: Dromaeosauridae), from Patagonia, Argentina: new insights on the unenlagine teeth

F. A. GIANECHINI; S. APESTEGUÍA; P. J. MAKOVICKY

San Rafael, Mendoza

Jornada; XXIV Jornadas Argentinas de Paleontología de Vertebrados; 2009

Buitreraptor gonzalezorum Makovicky, Apesteguía and Agnolín is a dromaeosaurid included within the Gondwanan clade Unenlagiinae. Among the unenlagine, only Buitreraptor and Austroraptor cabazai Novas, Pol, Canale, Porfiri and Calvo preserve in situ teeth. They have a suite of characters that, considered as a whole, are unusual among dromaeosaurids and that could be included as new Unenlagiinae synapomorphies. These features are: 1) high number of dental pieces; 2) teeth reduced in size respect to the skull height; 3) total absence of carinae and denticles; 4) presence of ridges and grooves on the lateral sides of the crown. These associated features, also observed in Austroraptor, are very different from those commonly present in laurassic dromaeosaurids. On the other hand, the teeth of Buitreraptor have features not observed in the teeth of Austroraptor, which can be considered as autopomorphic of Buitreraptor. These unique characters are: high lateral compression of the crown, and an eightshaped basal section. Some characters present in the teeth of Buitreraptor and Austroraptor are observed in other dromaeosaurids, and also in others deinonychosaurians like troodontids or even in others theropods out of Deinonychosauria (e.g. Compsognathidae). However, the suite of features observed in the unenlagine teeth is synapomorphic for this clade. The dental morphology present in Unenlagiinae, completely different from that of laurasian lineages, supports the vicariant condition for the evolution of southern dromaeosaurids.