Thanks to plenty of good press from movies, documentaries, books and toys, over the past thirty years, Deinonychus and Velociraptor have become the quintessential dromaeosaurid ("raptor") dinosaurs. They even rival the "Prize Fighter of Antiquity"—Tyrannosaurus rex—in fame these days. But these two sickle-clawed dinosaurs represent only part of a diverse group of animals that were widespread over the globe during the Cretaceous.
Among the strangest cousins of Velociraptor were a group of dromaeosaurids from the Southern Hemisphere called the Unenlagiinae (try saying that ten times fast). Only of handful of species—Buitreraptor, Unenlagia and Austroraptor from South America, plus Rahonavis from Madagascar—are known, but these slender, long-snouted raptors were distinct from species found anywhere else. Among the features that really set them apart are their teeth, which have just been analyzed in study by Federico Gianechini, Peter Makovicky and Sebastian Apesteguia soon to be published in the journal Acta Palaeontologica Polonica.
After looking at the preserved jaws of Buitreraptor and Austroraptor, Gianechini and co-authors were able to ascertain several specializations. Both had comparatively high numbers of teeth, small teeth for their skull size, a lack of serrations on their teeth and long grooves running up and down the tooth crown. Individually these tooth traits are also seen among various other theropod dinosaurs, but when they are all taken together they distinguish dinosaurs like Austroraptor from its dromaeosaurid relatives. Looking ahead, the recognition of these features may help paleontologists better identify which groups of raptors were present at a particular place and time on the basis of teeth alone.
The teeth may also tell us something about the feeding habits of these dinosaurs. Grooved teeth lacking serrations have are also present in a variety of dinosaurs and other prehistoric reptiles that ate fish, and it is possible that Buitreraptor and Austroraptor regularly fished for dinner. This hypothesis is not studied in detail—it is merely mentioned as an aside in the conclusion—but it is an angle worth looking into through future research.
Federico A. Gianechini, Peter J. Makovicky, and Sebastián Apesteguía (2010). The teeth of the unenlagiine theropod Buitreraptor from the Cretaceous of Patagonia, Argentina, and the unusual dentition of the Gondwanan dromaeosaurids. Acta Palaeontologica Polonica, in press