Most dinosaurs were veggie, new study shows

Published on Monday 20 December 2010 13:03

Historical inaccuracies aside, even if dinosaurs had roamed the earth around one million years BC, Raquel Welch would probably have not had to spend as much time running away from them as she did in the famous film.

Aside from the fact that humans arrived a good 65 million years after the big beasts had died out, scientists now believe many species of dinosaur previously believed to be meat eaters were actually vegetarian.

A new study of 90 species of theropod - two legged predatory dinosaurs - has discovered that 44 were vegetarian - and many others developed a taste for nuts seeds and fruit as well as eating meat.

Although the most well known of the theropods, Tyrannosaurus Rex and the velociraptor, were carnivores, researchers from the Chicago Field Museum believe dinosaurs evolved to lose their taste for meat.

Dr Lindsay Zanno of the Chicago Field Museum said: "Most theropods are clearly adapted to a predatory lifestyle, but somewhere on the line to birds, predatory dinosaurs went soft."

Among theropod dinosaurs, all modern birds and several groups of their closest extinct relatives belong to a subgroup known as Coelurosauria.

Most were feathered and the majority of the intelligent dinosaurs and those with the smallest body sizes also belong to this group.

In trying to establish the diet of dinosaurs scientists are left with just fossilized bones and teeth to work with and so had to deduce their diets.

By studying fossilized dinosaur dung, stomach contents, and tooth marks stones within the stomach, the US researchers were able to shed light on the mystery.

Dr Zanno said: "Once we linked certain adaptations with direct evidence of diet, we looked to see which other theropod species had the same traits. Then we could say who was likely a plant eater and who was not."

Many coelurosaurian dinosaurs have more ambiguous adaptations such as peg-like teeth at the front of the mouth, or no teeth at all, so determining their diet has been a challenge.

Dr Zanno said: "These oddball dinosaurs have been the subject of much speculation but until now, we have not had a reliable way to choose between competing theories as to what they ate."

Applying their data on diet, the researchers found that 44 theropod species distributed across six major lineages were eating plants and that the ancestor to most feathered dinosaurs and modern birds had probably already lost its appetite for flesh alone.Because plant eating was found to be so widespread the researchers say the carnivorous habits of T Rex and other meat eating coelurosaurs like velociraptor should be viewed "more as the exception than the rule."