As you know, while dinosaurs walked, their vertebral column moved in a parasagittal plane. List two modifications of the pelvis that appeared in the ancestral dinosaur. As you have seen, several modifications in the pattern of skull fenestrae have evolved during tetrapod history. Name the two kinds of animals that are included in the group Lepidosauria. Name one synapomorphy of that lineage that includes humans.
Pachycephalosaurs also have strange modifications of their skulls.
Name the modification and describe its probable function. At present, ceratopsian dinosaurs are only found in North America and Asia. Why or why not. By now you have learned the various skeletal synapomorphies that distinguish ornithischians from other dinosaurs.