Buitreraptor gonzalezorum: A Look at Dromaeosaur Feeding Styles.
Size: 4.3 feet (1.3 meters).
Time Period: The Cenomanian-Turonian Stage of the Early Late Cretaceous.
Locale: The Candeleros Formation of Argentina.
Name: The generic name means “vulture-roost thief,” from the Spanish buitre, which means vulture. The area where its remains were found is named La Buitrera, which literally means “vulture roost.”
The dromaeosaurs are now some of the most iconic theropods, thanks to the frequent documentary and movie portrayals of creatures such as Velociraptor. In every portrayal, the dromaeosaurs are depicted as big-game hunters of some kind. In Walking With Dinosaurs, a duo of Utahraptor hunt Iguanodon (disregarding that this was set in Europe, where Utahraptor was never even found). Deinonychus are always shown jumping onto the flanks of Tenontosaurus that just happen to be hanging around. Velociraptor is always beating the tar out of Protoceratops, or (in extreme cases) hunting little kids. But as I’ve said before, groups are capable of having more than one main niche.
A case in point is the more poorly known subfamily of the Dromaeosauridae, Unenlagiine. They probably lived in South America even before the continents split, and didn’t end up becoming as major faunal components as their northern relatives. They evolved short arms, flattened, small and unserrated teeth, and a very elongated body. Buitreraptor, a rooster-sized unenlagiine, is the earliest known representative of its family. The unenlagiines were probably creatures that adapted to a different niche than Velociraptor, Utahraptor, or any other dromaeosaurids due to the isolation of South America at the time. It’s possible that the small-predator roles filled by small dromaeosaurids in the Northern Hemisphere were already filled by the noasaurid ceratosaurs, provoking this unusual evolutionary side-road.
The teeth of Buitreraptor are very telling in terms of what niche it probably occupied. While more famous theropods like Tyrannosaurus, Allosaurus, and even Velociraptor had teeth with steak-knife serrations for cutting meat and attacking larger prey, Buitreraptor’s teeth lacked such serrations, and consequently looked similar to the teeth of modern alligators and crocodiles, as well as another famous theropod, Spinosaurus. This is a hint that Buitreraptor, and even its almost 6-meter long relative Austroraptor, ate prey that was smaller than them. They may have eaten small lizards, baby dinosaurs, or even fish. The long snout of these animals, combined with the unserrated teeth, actually parallels the feeding style of the spinosaurs. I wouldn’t be surprised if unenlagiines were found with fossils of fish or small animals near them.
The unenlagiines weren’t limited to South America, either. Rahonavis of Madagascar is another representative of the family, and some features of its body suggest that it had a volant lifestyle. This shows that flight was presumably lost in the ancestors of Rahonavis, but then re-evolved flight, probably to exploit niches that were open in the island environment of Madagascar. Like I’ve mentioned before, the Unenlagiine also contained giants like Austroraptor, which seemed even more like the spinosaurids than Buitreraptor did. Unidentified dromaeosaurid-like teeth from Australia may be attributable to unenlagiines.
So, Buitreraptor is no big-game hunter. There should be no illustrations of it leaping on the flanks of some innocent dinosaur or running around the heels of its titanosaurian contemporary Andesaurus. Its possible fish-eating lifestyle shows that the dromaeosaurids diversified in unpredicted ways because of their isolation. These dinosaurs are fairly rare in the fossil record, and if we find more remains of the unenlagiines, you can be sure that I’ll be back on this blog talking about them, and I’ll mention this post while I do it.