A view of Split Mountain in Dinosaur National Monument during a summer storm as sunset approaches. Split Mountain is a sharp meander, carved out of the surrounding desert landscape by the Green River, a tributary of the mighty Colorado River. The Green River originates in the Wind River Mountain Range in southeastern Wyoming to the north. Dinosaur National Monument as the name suggests is a world renowned locality for dinosaur fossils, with nearly 800 paleontological sites located in the park. It is known for the Allosaurus, Deinonychus, and Abydosaurus dinosaurs. Dinosaur National Monument is located on the Utah/Colorado border.