Tyrannosaurus rex may have been a fearsome carnivore, but many of its closest relatives were vegetarians, according to a new study. Fossils don't typically include definitive evidence of diet such as stomach contents, so most close relatives of T. rex and their fearsomely toothy kin—all of which belong to a group of dinosaurs known as theropods—were believed to be meat-eaters, too. But many theropod species discovered in the last decade contained evidence of a predominantly plant diet, such as gastroliths, or stomach stones, used to grind vegetation after it had been swallowed. In the new study, published  online today in the Proceedings of the National Academy of Sciences, researchers analyzed the anatomical features of 90 species of coelurosaurs, a subgroup of theropods that includes T. rex. They found more than 20 traits that were statistically linked to vegetarianism, including having a long neck (which helped the creatures graze more efficiently), a toothless beak, and a mixture of tooth types that included ones suited to shredding vegetation rather than shearing flesh. Of the 90 coelurosaur species the researchers studied (some of which are seen in the picture above), 44 were found to be herbivores. So the Jurassic period just got a bit less dangerous for small, delicious prey.
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