Monday, December 20, 2010

T. rex ancestors were Vegetarians, New study finds


Bird-like dinosaurs long assumed to be carnivorous predators were in fact plant lovers, with the notable exclusion of dedicated hunters such as T. rex, US paleontologists said Monday.

Peter Makovicky and Lindsay Zanno of the Field Museum in Chicago used statistical analysis to conclude that 90 species of Theropod dinosaurs ate a plant-based diet, especially among Coelurosaurs, the most bird-like dinosaurs.

The results were in sharp contrast to a widespread belief among paleontologists who say theropod dinosaurs hunted their prey, especially those closest to the ancestors of birds.

Zanno and Makovicky found nearly 2 dozen anatomical features were statistically linked to direct evidence of plant eating among Coelurosaurian dinosaurs, such as the loss of teeth or a long neck.

Through their analysis, the researchers found that 44 Theropod species distributed across 6 major lineages ate plants and that the ancestor to most feathered dinosaurs and modern birds had probably already stopped eating meat only during the Cretaceous Period, some 145-65 million years ago.

In light of the large number of plant eaters during that period, the carnivorous diet of T. rex, Velociraptor and other meat-eating coelurosaurs should be viewed "more as the exception than the rule," Zanno said.

The researchers also suggested that these big predators and their close relatives may have in fact evolved from omnivorous ancestors.

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