The Hell Creek Formation in what's now the Dakotas, Montana, and Wyoming was once home to some of the world's most beloved dinosaurs, like Triceratops and Tyrannosaurus rex (including SUE, one of the largest, most complete, and best-preserved T. rex specimens ever found).

Scientists describe two new species of birds that lived alongside these dinosaurs 68 million years ago. The researchers were able to name these new species from just one bone each: the powerful foot bone that suggests these birds could have captured and carried off prey.

While they might not be the first birds of prey to ever evolve, their fossils are the earliest known examples of predatory birds.

The math corroborated the researchers’ hypothesis that these feet would have been strong enough for these hawk-sized birds to pick up small mammals and even baby dinosaurs.

All of these birds are part of a group called the avisaurids. They belong to a larger group of birds called the enantiornithines, which went extinct with most of their fellow dinosaurs when the asteroid hit 66 million years ago.