November 29, 2012 When I was first becoming acquainted with
dinosaurs in the mid 1980s, “theropod” was synonymous with
“carnivorous dinosaur.” Large or small, from Tyrannosaurus to
Compsognathus, every theropod I knew of sustained itself on the
flesh of other organisms. But it was just about that time that
new discoveries and analyses revealed that many theropod
dinosaurs were omnivores, or even herbivores. The ostrich-like
ornithomimosaurs, beaked oviraptorosaurs and utterly bizarre
therizinosaurs, in particular, embodied a switch from an
ancestral meat-filled diet to one more reliant of fruit and
foliage. Not only that, but these herbivorous theropods grew
almost as large as the biggest carnivores–the ornithomimosaur
Deinocheirus, the ovriraptorosaur Gigantoraptor and
Therizinosaurus were all enormous Cretaceous dinosaurs. But why
did these plant-chomping dinosaurs become giants? In the latest
of a spate of papers considering herbivorous theropods,
paleontologists Lindsay Zanno and Peter Makovicky paired ev