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Herrerasaurus (meaning "Herrera's lizard," after the name of the rancher who discovered the first fossil of the animal) was one of the earliest dinosaurs. All known specimens of this carnivore, about 28 in total, have been discovered in northwest of Argentina, in Late Triassic Period rocks (early Carnian stage, around 228 million years ago). The type species, Herrerasaurus ischigualastensis, was described by Osvaldo Reig in 1963 and is the only species assigned to the genus. For many years, the classification of Herrerasaurus was unclear, as the animal was initially known from very fragmentary remains; it has been hypothesized to be a basal theropod, a basal sauropodomorph, a basal saurischian, or not a dinosaur at all. However, with the discovery of a mostly-complete skeleton and skull in 1988, Herrerasaurus has been classified as either an early theropod or an early saurischian in at least five recent surveys of theropod evolution. This medium-sized bipedal reptile is a member of the Herrerasauridae, a group of similar animals which were among the earliest of the dinosaurian radiation. (Read more...)

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