Acheroraptor

What it was like

Acheroraptor was a dromaeosaurid, a feathered hunter from the same family as Velociraptor and Deinonychus. It is known mostly from jaw bones and teeth, so its full size and shape are not known, but like its relatives it probably had a large sickle claw on each foot and ran on two legs.

Its world

It lived about 72 to 66 million years ago, at the very end of the Cretaceous, in what is now Montana, South Dakota and Wyoming. Its fossils come from the Hell Creek and Lance formations, which makes it one of the last raptors before the extinction.

It shared its world with Tyrannosaurus, Triceratops, Ankylosaurus, Pachycephalosaurus and Edmontosaurus. As a much smaller hunter, it probably went after small animals rather than these giants.

How it was found

Evans and colleagues named Acheroraptor in 2013. For many years, raptor teeth from these rocks had no name to go with them; Acheroraptor finally gave one. Three finds are known.