12" Fossil Juvenile Hadrosaur (Brachylophosaurus) Ulna - Montana

Hadrosaurs are frequently referred to as duck-billed dinosaurs and are members of the Ornithischian family Hadrosauridae. They were fairly common herbivores that roamed Asia, Europe, and North America during the Upper Cretaceous Period. Many species of Hadrosaurs had distinctive crests on their heads, some of which had air-filled chambers that may have produced a distinct sound. These crests may have been used for both audio and visual display purposes.

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.