Once thought to be the largest raptor ever, Megaraptor is now known to be more closely related to the allosaurids. It was certainly large, 26 feet long and about 1 ton. The sickle claw on it's hand was the first fossil of this dinosaur discovered. This is what caused the theory that it was a raptor to come about. Megaraptor lived in South America about 90 million years ago.