Henry Fricke of Colorado College says huge herds of plant-eating Camarasaurus, one of the most common species of sauropod, lived in Wyoming and Utah in the late Jurassic on what was once a low-lying floodplain that would have periodically dried out. Fricke wondered if they migrated to nearby hills to find food and water during the dry season, and turned to fossilized dinosaur teeth to find out, NewScientist.com reported Wednesday.
Oxygen isotope ratios in the fossil teeth vary depending on the water the dinosaurs drank, Fricke said, and he found the ratio in many teeth was different from that in carbonate rock from the floodplain that carries the signature of the water it formed in.
This suggests that Camarasaurus sometimes left the area, he said.
Although paleontologists have long suspected some dinosaurs migrated seasonally, this is the first solid evidence of such events, Paul Barrett of the Natural History Museum in London said.
It's likely Camarasaurus had company on the long treks in the form of predators like Allosaurus, a cousin of T. Rex, he said.
"A mass migration is basically a huge walking supermarket," Barrett said.