Herrerasaurus is a genus of dinosaur belonging to the group Herrerasauridae. It lived during the Late Triassic period, approximately 231 to 228 million years ago, making it one of the earliest dinosaurs to roam the Earth. The first fossils of Herrerasaurus were discovered in the Ischigualasto Formation of northwestern Argentina in the 1960s. Since then, additional findings have allowed scientists to reconstruct its remarkable story.

Herrerasaurus was a lightly built bipedal carnivore with a long tail and a relatively small head. It had long sickle shaped claws and opposable thumbs in its hands. This type of hand was efficent in attacking and grabbing prey. The hands also foreshadowed those of later theropods. But what was different from other theropods hands (except Eoraptor) was that it had five fingers. Herrerasaurus was a relatively small theropod dinosaur, measuring around 16 to 20 feet (4.8 to 6 meters) in length and standing approximately 7 feet (2.1 meters) tall at the hips. Its body was slender and agile, with a long tail that likely provided balance and stability during movement.

One of the defining features of Herrerasaurus was its powerful hind limbs, adapted for swift locomotion. Its forelimbs, though shorter, were armed with sharp claws that were likely used for grasping and seizing prey.

This dinosaur was named after a goat farmer named Victorino Herrera who found the skeleton that it belonged to in 1963, nort-western Argentina. It´s one of the oldest known dinosaurs and a very primitive theropod. Same as with other theropods, its bones were hollow, it had serrated teeth and both its upper jaw and lower jaw had a joint that allowed the mouth to open widely whilst the dinosaur was feeding.