Herrerasauria is a clade of basal saurischian dinosaurs, which includes the family Herrerasauridae. Their first fossil record was dated to the Carnian stage of the Late Triassic Period (233.23 million years ago), and the group probably gone extinct by the end of the Carnian stage. These were small-sized predatory dinosaurs with a maximum length of 4-6 meters. Their fossils were found primarily in South America, but possible herrerasaurid fossils were also found later in North America. Presumably, they occurred in other continents, too. Though their appearance resembles for later theropods, this similarity is only superficial; they are not considered to be the ancestors of any other later dinosaur groups. Their specialized and uniqe anatomy clearly distinct them from any dinosaur groups of the Jurassic and Cretaceous periods[1][2][3][4].

Scientific references

[1] Reig, O.A. (1963): La presencia de dinosaurios saurisquios en los "Estratos de Ischigualasto" (Mesotriásico Superior) de las provincias de San Juan y La Rioja (República Argentina). Ameghiniana (in Spanish). 3 (1): 3-20.

[2] Sereno, P.C.; Novas, F.E. (1992): The complete skull and skeleton of an early dinosaur. Science, 258 (5085): 1137-1140. a href="https://doi.org/10.1126/science.258.5085.1137" target="_blank"> doi: 10.1126/science.258.5085.1137.

[3] Steel, R. (1970): Part 14. Saurischia. Handbuch der Paläoherpetologie/Encyclopedia of Paleoherpetology. Gustav Fischer Verlag, Stuttgart: 1-87.

[4] Novas, F.E. (1992): Phylogenetic relationships of the basal dinosaurs, the Herrerasauridae. Palaeontology, 35 (1): 51-62.