Scientists have used statistical analyses to determine that for 90 species of theropod dinosaurs, especially the most bird-like dinosaurs—known as coelurosaurs—plant eating was a common way of life.Unlike Tyrannosaurus rex with its bone-crunching teeth, many coelurosaurian dinosaurs have peg-like teeth at the front of the mouth or no teeth at all so determining their diet has been a challenge.
Fortunately a small percentage of these species also preserve clear-cut evidence of diet with their skeletal remains. Fossilized dinosaur dung, stomach contents, tooth marks, the presence of stones within the stomach that serve as a gastric mill for digesting vegetation, and even two dinosaur species preserved locked in the throes of combat all provide a direct window on diet. After collecting dietary data for almost 100 coelurosaur species, the researchers found that almost two dozen anatomical features could be linked to direct evidence of herbivory including a toothless beak.
Because plant eating was found to be so widespread in Coelurosauria, the hypercarnivorous habits of T. rex and other meat eating coelurosaurs like Velociraptor should be viewed more as the exception than the rule.
The resesrchers also found that a toothless beak only evolved in lineages known to have had a gastric mill for grinding plants. In lineages where a gastric mill is not yet known, such as the bizarre, sickle-clawed therizinosaurs, the species retain teeth at the back of the mouth for shredding plant material.
Because ceolurosaurian dinosaurs include the closest extinct relatives of birds, understanding their biology is also extremely important to understanding how, why, and under what conditions birds evolved and first took flight. link.
Dear Field Museum Press People: Surely the FM has put out a press release since last August. I'd suggest updating your press page, especially when you provide links to out of date sites.