Buitreraptor was described in 2005. The type species is Buitreraptor gonzalezorum. It was rooster-sized and had a very elongated head with many small teeth.
Buiteraptor was a rather small species. In 2010 Gregory S. Paul estimated the length at 1.5 metres, the weight at three kilograms.
Buitreraptor has some different physical features than typical northern dromaeosaurs, such as Velociraptor.
Buitreraptor has a slender, flat, extremely elongated snout with many small teeth that lack meat-tearing serrations or cutting edges and are grooved, strongly recurved and flattened. From this, the scientists who initially described it concluded that this dinosaur was not a hunter of relatively large animals like some other dromaeosaurs, but rather a hunter of small animals such as lizards and mammals. The forelimbs of Buitreraptor were long and ending in hands with three fingers. The fingers were proportionarly shorter than in other dromaeosaurids, and of essentially the same length, contrary to most of its relatives, which had fingers of different length, with the second finger being considerably longer.
The body as a whole was also very elongated, with a shallow ribcage. The sickle claw at the second toe of the foot was relatively short and broad.
No fossil discoveries have been made of any feathers of Buitreraptor. However, there are relatives like Microraptor and Sinornithosaurus, of which fossils with preserved feathers are known. Since its close relatives had feathers, it is likely that Buitreraptor also was feathered. According to Apesteguia, this is comparable to reconstructing an extinct monkey with fur because all modern monkeys have fur.
Other than Buitreraptor, the only other known dromaeosaurs from the southern continents are Neuquenraptor, Austroraptor, and Unenlagia from South America (discovered earlier in 2005), Rahonavis (once thought to be a true avian bird) from Madagascar, and unidentified dromaeosaur-like teeth from Australia. This discovery in the Southern Hemisphere helped scientists to clarify that the dromaeosaur family was more widely dispersed around the world than previously thought. Evidence indicates that dromaeosaurs first appeared during the Jurassic Period, when all the continents were much closer together than they are today. With the discovery of Buitreraptor, the scientists proposed that dromaeosaurids originated somewhere around 180 million years ago, before Pangaea broke up. However, other paleontologists have in later studies placed the time of origin for dromaeosauridae to about 160 million years ago.
The scientists see it as an alternative possibility that dromaeosaurids originated on the ancient continent Laurasia in the north and during the Cretaceous Period migrated to southern Gondwana, since the species known from the Southern Hemisphere bear distinctive characteristics not shared by their northern relatives. La Buitrera also yielded remains of terrestrial crocodiles, pterosaurs, the largest known rhynchocephalians, limbed snakes, iguanian lizards, chelid turtles, mammals, and dipnoan fishes.