Dinosaurs were the result of the evolutionary changes that took place in reptiles during the Paleozoic Era. This chapter discusses the taxonomy and evidence of dinosaur fossils in California. Dinosaurs arose from one branch of the diapsids, a group of reptiles characterized with two holes in the skull behind the eye socket. One of the most diagnostic traits separating dinosaurs not only from mammals but also from their reptilian relatives is the numerous and unique positioning of the openings and cavities found in the bones of the skull. Because all dinosaurs are diapsids, they have two pairs...

Dinosaurs were the result of the evolutionary changes that took place in reptiles during the Paleozoic Era. This chapter discusses the taxonomy and evidence of dinosaur fossils in California. Dinosaurs arose from one branch of the diapsids, a group of reptiles characterized with two holes in the skull behind the eye socket. One of the most diagnostic traits separating dinosaurs not only from mammals but also from their reptilian relatives is the numerous and unique positioning of the openings and cavities found in the bones of the skull. Because all dinosaurs are diapsids, they have two pairs of main openings behind the eye. The great majority of the dinosaur fossils found in California are from the Cretaceous Period. Dinosaurs from this period have been found from southern Oregon, throughout the length of California, and into northern Baja California. Hadrosaurs were perhaps the most common dinosaur to have inhabited the Pacific coastal region of California, and indeed, more fossil hadrosaurian remains have been found in California than those of any other dinosaur.