Camarasaurus
There is a fossil record of two adults and a 12.2 meter (40 ft) long juvenile that died together in the late Jurassic leriod, about 150 million years ago (northeast Wyoming). It is assumed that their bodies were washed to their final resting place, in river mud. This suggests that Camarasaurus traveled in herds or, at least, 'family' groups. Also, recovered camarasaur eggs have been found in lines, rather than in neatly arranged nests as with some other dinosaurs, which appears to suggest that, like most sauropods, Camarasaurus did not tend its young.