What is the X in X-mas?
Any of various dinosaurs belonging to the group Saurischia, one of the two main divisions of dinosaurs. Saurischians had a pelvis similar to that of modern reptiles, in which the pubis pointed forward. Saurischians include all the carnivorous dinosaurs (theropods) as well as the herbivorous sauropods, and often grew to great size. Birds are descended from one group of saurischians. Compare ornithischian.