“Herrera’s lizard” was discovered in 1958 in San Juan, Argentina, by Victorino Herrera, and was described by Osvaldo Reig in 1963. Herrerasaurus lived about 231 million years ago, during the Ladinian epoch of the Middle Triassic. The dinosaur measured 3-6 m (9.8-19.6 ft) in length, 1.1 m (3.6 ft) tall, and weighed from 210-350 kg (463-771.6 lbs). Herrerasaurus was found in the Ischigualasto Formation, from which its species name is derived. The animal was relatively unknown for years, until Paul Sereno made an expedition to South America and discovered its skull; even so, the exact taxonomic placement of Herrerasaurus is unclear. Many place it as a basal theropod in the roots of the saurischian tree.
Herrerasaurus existed on Isla Nublar; though it was never seen on the tour, it definitively existed in the park. Herrerasaurus was listed on the JP Brochure Map found in the Ford Explorer tour vehicles. A pack of herrerasaurs also threatened Gerry Harding, Jess Harding, and Nima Cruz as they attempted to descend a cliff via the Bone Shaker roller coaster, near where their paddock was, but were driven off by Billy Yoder and Oscar Morales. On their way back to the mercenaries’ helicopter, Dr. Harding told Yoder that the cloning of the herrerasaurs had allowed them to confirm that they were basal theropods; Yoder sarcastically claimed that he had always known that the “hairy-sauruses” were exactly that. Herrerasaurus may exist on Isla Sorna, as InGen originally cloned them there, though there is no evidence to suggest that they still do.