Camarasaurus is a genus of very large sauropod dinosaur in the family Camarasauridae. Its fossils are known from western North America. It originally lived during the late Jurassic period, specifically the Kimmeridgian to Tithonian ages, between 155 and 145 million years ago. There are at least three known species: the type and largest species Camarasaurus supremus, the smaller Camarasaurus lentus, and the geologically older Camarasaurus grandis. There may be a fourth species, Camarasaurus lewisi, the smallest of the bunch.