Some dinosaur species apparently lived in groups, as revealed by fossil evidence, which includes:
- many fossils found together in bone beds (large deposits of bones of the same species in an area)
- fossilized track ways of many dinosaurs travelling together
- large groups of fossilized nests grouped together.
Some dinosaurs may have grouped together for protection like Hypsilophodon, and some may have cooperated for more effective hunting like Velociraptor. Some herds may have been temporary, however, with the dinosaurs simply congregating temporarily at rich feeding grounds.
Many plant-eating dinosaurs travelled in herds, feeding and perhaps nesting and migrating together. The advantage of congregating in herds was primarily in protection against predators (meat-eating animals).
Maiasaura fossils have been found in a huge group of about 10,000 animals. This strongly indicates herding behavior. These Maiasauras were buried in volcanic ash along with a field of nests and eggs.
Several hundred Coelophysis fossil skeletons have been found in Arizona, New Mexico, and perhaps Utah. Adults and juveniles of this meat-eating dinosaur have been found.
Other dinosaurs that may have travelled in groups were Ornithomimus and Dryosaurus.