Anatomy: This small genus of meat-eating dinosaurs was about 6.5 feet (2 m) long. The skull alone was about 12 inches (30 cm) long and contained many sharp teeth. Unlike other dinosaurs (who walked on their toes) this new reptile was flat-footed (like thecodonts). The backbone and skull were more like those of dinosaurs.

When it Lived: This as-yet-unnamed dinosaur/thecodont lived from about 235 to 240 million years ago, during the Triassic period.

Fossils: The fossils, two skulls and some other bones, were found in southern Brazil, in the state of Rio Grande do Sul, about 155 miles (250 km) west of the city of Porto Alegre.

Other Old Dinosaurs: Previously, the oldest-known dinosaurs were prosauropods from Madagascar (230 million years old) and 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.