Ornithischia is an extinct clade of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name Ornithischia, or "bird-hipped", reflects this similarity and is derived from the Greek stem ornith- (ὀρνιθ-), meaning "bird", and ischion (ἴσχιον), meaning "hip". However, birds are only distantly related to this group as birds are theropod dinosaurs. Ornithischians with well known anatomical adaptations include the ceratopsians or "horn-faced" dinosaurs, the pachycephalosaurs or "thick-headed" dinosaurs, the armored dinosaurs (Thyreophora) such as stegosaurs and ankylosaurs, and the ornithopods. There is strong evidence that certain groups of ornithischians lived in herds, often segregated by age group, with juveniles forming their own flocks separate from adults. Some were at least partially covered in filamentous pelts, and there is much debate over whether these filaments found in specimens of Tianyulong, Psittacosaurus, and Kulindadromeus may have been primitive feathers.
Eucoelophysis is a genus of silesaurid dinosauriform from the Late Triassic (Norian) period Chinle Formation of New Mexico. It was assumed to be a coelophysid upon description, but a study by Nesbitt et al. found that it was actually a close relative of Silesaurus, which was independently supported by Ezcurra (2006), who found it to be the sister group to Dinosauria, and Silesaurus as the next most basal taxon.
Guaibasaurus is an extinct genus of basal saurischian dinosaur known from the Late Triassic Caturrita Formation of Rio Grande do Sul, southern Brazil. Most analyses recover it as a sauropodomorph, although there are some suggestions that it was a theropod instead. In 2016 Gregory S. Paul estimated it at 2 meters and 10 kg, whereas in 2020 Molina-Pérez and Larramendi listed it at 3 meters and 35 kg.
Technosaurus is an extinct genus of Late Triassic silesaurid dinosauriform, from the Late Triassic Cooper Canyon Formation of Texas, United States.
Pisanosaurus is an extinct genus of early dinosauriform, likely an ornithischian or silesaurid, from the Late Triassic of Argentina. It was a small, lightly built, ground-dwelling herbivore, that could grow up to an estimated 1 m (3.3 ft) long. Only one species, the type, Pisanosaurus mertii, is known, based on a single partial skeleton discovered in the Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina. This part of the formation has been dated to the late Carnian, approximately 229 million years ago.
Lagerpeton is a genus of lagerpetid avemetatarsalian, comprising a single species, L. chanarensis. First described from the Chañares Formation of Argentina by A. S. Romer in 1971, Lagerpeton's anatomy is somewhat incompletely known, with fossil specimens accounting for the pelvic girdle, hindlimbs, posterior presacral, sacral and anterior caudal vertebrae. Skull and shoulder material has also been described.
Lewisuchus is a genus of archosaur that lived during the Late Triassic. As a silesaurid dinosauriform, it was a member of the group of reptiles most commonly considered to be the closest relatives of dinosaurs. Lewisuchus was about 1 metre (3.3 ft) long. Fossils have been found in the Chañares Formation of Argentina. It exhibited osteoderms along its back.
Nyasasaurus is an extinct genus of avemetatarsalian archosaur from the putatively Middle Triassic Manda Formation of Tanzania that may be the earliest known dinosaur. The type species Nyasasaurus parringtoni was first described in 1956 in the doctoral thesis of English paleontologist Alan J. Charig, but it was not formally described until 2013.
Silesaurus is a genus of silesaurid dinosauriform from the Late Triassic, of what is now Poland.
Dinosauromorpha is a clade of avemetatarsalians that includes the Dinosauria (dinosaurs) and some of their close relatives. It was originally defined to include dinosauriforms and lagerpetids, with later formulations specifically excluding pterosaurs from the group. Birds are the only dinosauromorphs which survive to the present day.
Avemetatarsalia is a clade of diapsid reptiles containing all archosaurs more closely related to birds than to crocodilians. The two most successful groups of avemetatarsalians were the dinosaurs and pterosaurs. Dinosaurs were the largest terrestrial animals for much of the Mesozoic Era, and one group of small feathered dinosaurs has survived up to the present day. Pterosaurs were the first flying vertebrates and persisted through the Mesozoic before dying out at the Cretaceous-Paleogene (K-Pg) extinction event. Both dinosaurs and pterosaurs appeared in the Triassic Period, shortly after avemetatarsalians as a whole. The name Avemetatarsalia was first established by British palaeontologist Michael Benton in 1999. An alternate name is Pan-Aves, or "all birds", in reference to its definition containing all animals, living or extinct, which are more closely related to birds than to crocodilians.
Saurischia is one of the two basic divisions of dinosaurs, classified by their hip structure. Saurischia and Ornithischia were originally called orders by Harry Seeley in 1888 though today most paleontologists classify Saurischia as an unranked clade rather than an order.
Sacisaurus is a silesaurid dinosauriform from the Late Triassic (Norian) Caturrita Formation of southern Brazil. The scientific name, Sacisaurus agudoensis, refers to the city where the species was found, Agudo in the Rio Grande do Sul state, whereas Sacisaurus refers to Saci, a famous one-legged creature from Brazilian mythology, because among the dozens of fossil material unearthed, 35 right femora were collected whereas only 1 left femur was found.
Dromomeron is a genus of lagerpetid avemetatarsalian which lived around 220 to 211.9 ± 0.7 million years ago. The genus contains species known from Late Triassic-age rocks of the Southwestern United States and northwestern Argentina. It is described as most closely related to the earlier Lagerpeton of Argentina, but was found among remains of true dinosaurs like Chindesaurus, indicating that the first dinosaurs did not immediately replace related groups.
Asilisaurus ; from Swahili, asili, and Greek, σαυρος is an extinct genus of silesaurid archosaur. The type species is Asilisaurus kongwe.Asilisaurus fossils were uncovered in the Manda Beds of Tanzania and date back to the early Carnian, making it one of the oldest known members of the Avemetatarsalia. It was the first non-dinosaurian dinosauriform recovered from Africa. The discovery of Asilisaurus has provided evidence for a rapid diversification of avemetatarsalians during the Middle Triassic, with the diversification of archosaurs during this time previously only documented in pseudosuchians.
Diodorus is a genus of silesaurid dinosauromorph that lived during the Late Triassic in what is now Morocco. Fossils were discovered in the Timezgadiouine Formation of the Argana Basin, and were used to name the new genus and species Diodorus scytobrachion. The genus name honors the mythological king Diodorus and the ancient historian Diodorus Siculus; the specific name is ancient Greek for 'leathery arm' and also honors the mythographer Dionysius Scytobrachion. The holotype specimen is a partial dentary bone (front of the lower jaw), and assigned specimens include isolated teeth, two humeri (upper arm bones), a metatarsal (foot bone), and femur (thigh bone).
Nhandumirim is a genus of basal sauropodomorph dinosaur from the Carnian age of Late Triassic Brazil. It is currently considered a saturnaliid sauropodomorph. The type and only species, Nhandumirim waldsangae, is known from a single immature specimen including vertebrae, a chevron, pelvic material, and a hindlimb found in the Santa Maria Formation in Rio Grande do Sul.
Sulcimentisauria is a clade of derived silesaurid dinosauriforms. Sulcimentisaurian fossils have been found in North and South America, Europe, and Africa. It was defined as "the most inclusive clade that includes Silesaurus opolensis but not Asilisaurus kongwe".
Kwanasaurus is an extinct genus of silesaurid dinosauromorph reptiles from the Late Triassic of Colorado. It is known from a single species, Kwanasaurus williamparkeri. Kwanasaurus had a deeper, stronger skull and greater specialization for herbivory compared to other silesaurids. It also possessed many unique characteristics of the snout, ilium, and lower part of the femur. It was described along with new specimens of Dromomeron from the Eagle Basin, the northernmost extent of the Chinle Formation.
