Nova does a show about this!
EDIT: Never mind the above...tho this was what I watched and it was fascinating.
Artistic rendering of a newly discovered species of parrot-beaked dinosaur, Psittacosaurus gobiensis. Scientists first discovered psittacosaurs in the Gobi Desert in 1922, calling them "parrot-beaked" for their resemblance to parrots. Psittacosaurs evolved their strong-jawed, nut-eating habits 60 million years before the earliest parrot. © Todd Marshall
Paul Sereno(www.sciencedaily.com) Plants or meat: That's about all that fossils ever tell paleontologists about a dinosaur's diet. But the skull characteristics of a new species of parrot-beaked dinosaur and its associated gizzard stones indicate that the animal fed on nuts and/or seeds. These characteristics present the first solid evidence of nut-eating in any dinosaur.
JUNE 17, 2009 — "The parallels in the skull to that in parrots, the descendants of dinosaurs most famous for their nut-cracking habits, is remarkable," said Paul Sereno, (...)