About the size of a turkey vulture, a fossil found in the Grand Staircase-Escalante National Monument in Utah is not only one of the largest dinosaur-era birds ever found in North America, but it is also the continent’s most complete skeleton for a long-extinct group of birds called the enantiornithines.

The enantiornithines, or “opposite birds,” were a primitive lineage related to modern birds that thrived globally during the Cretaceous period but were killed off the by the same mass extinction event that wiped out the nonavian dinosaurs 66 million years ago.

While numerous beautiful specimens of enantiornithines have been found in early Cretaceous rocks in China and pieces of amber from Myanmar, most are no bigger than small- to medium-sized