New dinosaur species may be a missing link

Fossils of the lumbering Aardonyx celestae found in South Africa may explain why dinosaurs evolved from bipeds to quadrupeds.

Reporting from Johannesburg, South Africa - Before the dig started, it looked like any other patch of dinosaur dirt: gray soil, a few brownish fossilized bones exposed by erosion. Paleontologist Adam Yates thought his diggers would find a few bones from the massospondylus -- South Africa's most common dinosaur.

So the Australian paleontologist at the University of the Witwatersrand in Johannesburg initially assigned a master's student in 2006 to excavate the site and research the story of how the dinosaurs died.

But within days, it was clear that they were on to something big. In about 11 weeks spread over the years since, Yates' team members excavated about 300 bones from a site just over 20 feet long and 9 feet wide.

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