Definition: Crassileptodontium is a type of extinct dinosaurian known from the Late Cretaceous period, approximately 68 million years ago. It was a small theropod dinosaur with features characteristic of other dinosaurs such as a long neck and powerful jaws. The skull and jaw morphology were similar to those of modern crocodiles. Crassileptodontium lived in the Early Permian period and is believed to have been the first known dinosaur that resembled an extinct horse.