| Herrerasauridae | |
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| Herrerasaurus ischigualastensis | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Sauropsida |
| clade: | Dinosauria |
| Order: | Saurischia |
| Family: | †Herrerasauridae Reig, 1963 |
| Genera | |
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| Synonyms | |
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Herrerasauridae is one of the oldest recorded dinosaur families in the history of the species. Herrerasaurids appeared in the fossil record as early as 228 million years ago, in the mid to late Triassic Period. The family went extinct around conclusion of the Triassic Period.
Description[]
Herrerasaurid physiology resembled the later-appearing theropods, who may in fact be the early dinosaurs' closest relatives. However, as opposed to the larger theropods, hererrasaurids were small to medium-sized carnivores. The best known representative of the group is the type genus Herrerasaurus, which had a nearly complete skeleton discovered in 1988 in San Juan, Argentina. The genus itself was first discovered in 1960s. Fossil remains have also been discovered in North America, indicating the creatures inhabited other continents as well prior to the continental shift.
Herrerasaurids have a unique physiology and anatomy compared to other genus of dinosaurs, and are not generally considered to be an ancestral species to any later dinosaur group. The herrerasaurid structure represents a mixture of primitive and derived traits, indicative of its place in the early history of the dinosaurs. The acetabulum is only partly open, and the creature only has two sacral vertebrae, which is the lowest among all discovered dinosaurs. The hand structure of the creature is also of primitive design, in that herrerasaurids have five metacarpals and a third finger longer than the second. However, like the later theropods, the herrerasaurids have only three long fingers, with curved claws. Herrerasaurids also have a hinged mandible like theropods, but this may have evolved independently.
Phylogeny[]
| Dinosauria |
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