12" Hadrosaur (Brachylophosaurus?) Partial Ulna Bone - Montana

Brachylophosaurus was a Saurolophine Hadrosaur from the Late Cretaceous of western North America. As a Saurolophine, Brachylophosaurus was a quadrupedal herbivore with a duck-like snout and a battery of hundreds of chewing teeth for extensively grinding plant material. Brachylophosaurus is known for having a smaller and wider head than most other hadrosaurs of the time, and for having a small, flat crest over the back of its skull. The purpose of this crest is not quite known, but skull ornamentation is not uncommon in hadrosaurs. Like other hadrosaurs, Brachylophosaurus's forelimbs would have been enclosed in a fleshy "mitten", filling the role of hooves. As an inhabitant of the Judith River Formation, Brachylophosaurus would have formed groups to better defend themselves against predators, like the several species of Tyrannosaurid they shared their habitats with.

The Judith River Formation is one of the world's most prolific sources of Late Cretaceous vertebrate fossils. At least sixteen Orders containing more than forty Genera are known from the formation. These include fish, amphibians, mammals, and insects in addition to reptiles and avian (birds) and non-avian dinosaurs. Among the more interesting specimens is Leonardo, a mummified and fossilized Brachylophosaurus. This is a hadrosaur, a duck-billed dinosaur found with amazing soft-tissue preservation: skin impressions can be found on 90 percent of its body! The pattern in the skin on its feet is even preserved. In addition to Leonardo, the Judith River Formation contains the remains of the theropod Hesperornis, the only known freshwater Hespernorthid, a penguin-like bird.