As long as we're on the topic, not all of what we (the laymen) think of as dinosaurs were dinosaurs! Maybe you knew that already but I only recently discovered that fact and now I'm sharing it. From the wikipedia page:

"Other prehistoric animals, including mosasaurs, ichthyosaurs, pterosaurs, plesiosaurs, and Dimetrodon, while often popularly conceived of as dinosaurs, are not taxonomically classified as dinosaurs. Pterosaurs are distantly related to dinosaurs, being members of the clade Ornithodira. The other groups mentioned are, like dinosaurs, members of Sauropsida (the reptile and bird clade), with the exception of Dimetrodon (which is a synapsid)."