Gorgosaurus

Gorgosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, between about 77 and 74 million years ago. Like most known tyrannosaurids, Gorgosaurus was a bipedal predator weighing more than a metric ton as an adult; dozens of large, sharp teeth lined its jaws, while its two-fingered forelimbs were comparatively small.

A gorgosaur attacked the herd of hadrosaurs that Paula Shaffer was observing. As Paula was in the midst of the herd with an infant hadrosaur, she was caught up in the stampede the gorgosaur touched off. As the herd (and Paula) ran, another gorgosaur arrived, much to the anger of the first, which had felled one hadrosaur.