They estimate that meat-munching "Wall Raptor" was young when it died, but the well-preserved remains of the dinosaur indicate that it still grew to at least 21 feet.
The new dinosaur was not just any raptor, but a megaraptor, a term used to describe large, carnivorous two-legged dinosaurs from the Cretaceous. Perhaps the most distinguishing feature of megaraptors was the 14-inch-long sickle-like claw on the thumb of each of their forelimbs. The dinosaur's other digits were clawed, too.
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Megaraptors also had a tail that was probably used for quick turns and to help with balance. The bones of these dinosaurs were air-filled and bird-like. Together, the features suggest that these dinos were extremely agile hunters.
Wall Raptor was related to Megaraptor, Orkoraptor, and Aerosteon -- a trio of formidable South American carnivorous dinosaurs. Similar meat-eating dinosaurs have also been unearthed in Australia and Japan.
There has been a long-standing debate concerning how megaraptors should be classified. Some paleontologists have argued that the ancestors of megaraptors descended from Allosaurus, a genus of big carnivorous dinosaurs that lived 155 to 150 million years ago during the Late Jurassic.
Others have argued that megaraptors are more closely related to Tyrannosaurus, another dinosaur genus that has T. rex as its star.
The authors of this new study take a neutral stance, but suggest an answer to the puzzle could come soon. They're hoping that more megaraptors will be found "in older rocks from both South America and Australia" to paint a clearer picture of the overall family tree for the toothy megaraptors.