Herrerasaurus is one of the oldest known dinosaurs. It lived about 230 million years ago. It was a theropod dinosaur, meaning that it ate meat and ran on its back legs. It would also walk on all four legs when it was looking for food on the ground. Its bones were hollow and thin, which made it light for its size. It was probably a fast runner; we know this by studying its trackways, or footprints. Trackways that are far apart show us that it took big steps when it was running.
Herrerasaurus grew to be 13 feet long, which is about the size of a minivan. It was about four feet high and weighed about 460 pounds. This dinosaur was a carnivore, meaning that it ate meat. It would eat lizards and fish and other smaller dinosaurs such as Eoraptors. It was probably a deadly hunter. Its teeth were sharp and had jagged edges, like small saws. Herrerasaurus had an unusual joint in its jaw. This allowed it to open its mouth very wide.
Herrerasaurus had hands with five fingers and a thumb, like we have. But its fifth finger was probably too small to be seen. Its hands were very useful for grabbing things. It had short arms and sharp, curved claws on its fingers. We believe that it hunted alone, since its bones have not been found together with other Herrerasaurus skeletons. The fossilized bones of this dinosaur were found by a goat farmer named Don Victorino Herrera. Herrerasaurus means “Herrera’s lizard”, named for the farmer who discovered it. Herrerasaurus was first found in what is now the country of Argentina.