An international team of scientists led by John Flynn (of Chicago's Field Museum) found the fossils in a riverbed on Madagascar. The team included John Flynn, J. Michael Parrish (of the Northern Illinois University), Berthe Rakotosamimanana (of the Universite d'Antananarivo, Madagascar), William Simpson (of the Field Museum), and Robin Whatley and Andre Wyss (both from the University of California, Santa Barbara).

So far, only the jaw bones of these kangaroo-sized dinosaurs have been found. They were probably prosauropods, primitive, plant-eating dinosaurs that had a small head and a long neck. They walked on four legs, but could perhaps rear up on two legs to feed. The prosauropods may have led to the sauropods, familiar plant-eaters like Apatosaurus, Diplodocus, and Brachiosaurus.

Previously, the oldest-known dinosaur was Eoraptor, a meat-eater found in Argentina. Eoraptor dates from about 228 million years ago. The Eoraptor site was dated using radio-isotope analysis; the Madagascar site was dated using index fossils.

Reference: Nature (Sept. 2, 1999 ) and Science (Oct. 22, 1999). Press release.