Eoraptor is a genus of small, lightly built, basal sauropodomorph dinosaur. One of the earliest-known dinosaurs and one of the earliest sauropodomorphs, it lived approximately 231 to 228 million years ago, during the Late Triassic in Western Gondwana, in the region that is now northwestern Argentina. The type and only species, Eoraptor lunensis, was first described in 1993, and is known from an almost complete and well-preserved skeleton and several fragmentary ones. Eoraptor had multiple tooth shapes, which suggests that it was omnivorous.
Sauropodomorpha is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had long necks and tails, were quadrupedal, and became the largest animals to ever walk the Earth. The prosauropods, which preceded the sauropods, were smaller and were often able to walk on two legs. The sauropodomorphs were the dominant terrestrial herbivores throughout much of the Mesozoic Era, from their origins in the Late Triassic until their decline and extinction at the end of the Cretaceous.
Rhynchocephalia is an order of lizard-like reptiles that includes only one living species, the tuatara of New Zealand. Despite its current lack of diversity, during the Mesozoic rhynchocephalians were a speciose group with high morphological and ecological diversity. The oldest record of the group is dated to the Middle Triassic around 238 to 240 million years ago, and they had achieved global distribution by the Early Jurassic. Most rhynchocephalians belong to the group Sphenodontia ('wedge-teeth'). Their closest living relatives are lizards and snakes in the order Squamata, with the two orders being grouped together in the superorder Lepidosauria.
Sphenodontidae is a family within the reptile group Rhynchocephalia, comprising taxa most closely related to the living tuatara. Historically the taxa included within Sphenodontidae have varied greatly between analyses, and the group has lacked a formal definition. Cynosphenodon from the Jurassic of Mexico has consistently been recovered as a close relative of the tuatara in most analyses, with the clade containing the two and other very close relatives of the tuatara often called Sphenodontinae. The herbivorous Eilenodontinae, otherwise considered part of Opisthodontia, is considered to be part of this family in many recent studies as the sister group to Sphenodontinae. The earliest Sphenodontines are known from the Early Jurassic of North America, with other remains known from the Late Jurassic of Europe, the Late Cretaceous and possibly Paleocene of South America and the Miocene-recent of New Zealand. Sphenodontines are characterised by a complete lower temporal bar caused by the fusion of a forward directed process (extension) of the quadrate/quadratojugal and the jugal, which was an adaptation for reducing stress in the skull during hard biting. Other synapomorphies of Sphenodontinae include the presence of nasal foramina, a posterodorsal process of the coronoid of the lower jaw, the present of caniniform successional teeth at the front of the jaws, the presence of flanges on the posterior parts of teeth at back of the lower jaw, and an expanded radial condyle on the humerus. Like modern tuatara, members of Sphenodontinae were likely generalists with a carnivorous/insectivorous diet.
Planocephalosaurus is an extinct genus of basal rhynchocephalian. Fossils of the genus are primarily known from fissure fill deposits from the Late Triassic of southwest Britain, with fragmentary remains possibly belonging to the genus also known from the Late Triassic of Texas.
Clevosaurus is an extinct genus of rhynchocephalian reptile from the Late Triassic and the Early Jurassic periods. Species of Clevosaurus were widespread across Pangaea, and have been found on all continents except Australia and Antarctica. Five species of Clevosaurus have been found in ancient fissure fill deposits in south-west England and Wales, alongside other sphenodontians, early mammals and dinosaurs. In regards to its Pangaean distribution, C. hadroprodon is the oldest record of a sphenodontian from Gondwana, though its affinity to Clevosaurus has been questioned.
The Quebrada del Barro Formation is a geological formation of the Marayes-El Carrizal Basin in San Juan Province, Argentina. This formation is the most fossiliferous portion of the Triassic Marayes Group, and is also the youngest unit of the group, overlying the El Carrizal Formation. An unconformity at the top of the Quebrada del Barro Formation separates it from the Cretaceous-age Los Riscos Formation of the El Gigante Group. Part of the formation may be made into a provincial park following the discovery of the fossils of Ingentia, a giant sauropodomorph dinosaur which helped elucidate the early evolution of sauropods.
Diphydontosaurus is an extinct genus of small rhynchocephalian reptile from the Late Triassic of Europe. It is the most primitive known member of Sphenodontia.
Atopodentatus is an extinct genus of basal sauropterygian known from the early Middle Triassic (Anisian) of Guanling Formation in Luoping County, Yunnan Province, southwestern China. It contains a single species, Atopodentatus unicus. It is thought to have lived between 247 and 240 million years ago, during the Middle Triassic period, about six million years after the Permian extinction. Atopodentatus was an herbivorous marine reptile, although marine reptiles are usually omnivores or carnivores.
Cartorhynchus is an extinct genus of early ichthyosauriform marine reptile that lived during the Early Triassic epoch, about 248 million years ago. The genus contains a single species, Cartorhynchus lenticarpus, named in 2014 by Ryosuke Motani and colleagues from a single nearly-complete skeleton found near Chaohu, Anhui Province, China. Along with its close relative Sclerocormus, Cartorhynchus was part of a diversification of marine reptiles that occurred suddenly during the Spathian substage, soon after the devastating Permian-Triassic extinction event, but they were subsequently driven to extinction by volcanism and sea level changes by the Middle Triassic.
Priosphenodon is an extinct, large herbiviorous eilenodontine rhynchocephalian known from the mid-Cretaceous (Albian-Turonian) of Argentina. It is one of the largest known sphenodontians.
Caelestiventus is a pterosaur genus from the Late Triassic found in western North America. The type species, Caelestiventus hanseni, honors Robin Hansen, the Bureau of Land Management geologist (BLM), who facilitated access to the excavation site.
Opisthodontia is a proposed clade of sphenodontian reptiles, uniting Opisthias from the Late Jurassic-earliest Cretaceous of Europe and North America with the Eilenodontinae, a group of herbivorous sphenodontians known from the Late Triassic to Late Cretaceous.
Clevosaurs are an extinct group of rhynchocephalian reptiles from the Triassic and Jurassic periods.
Sapheosaurs are an extinct group of rhynchocephalian reptiles from the Late Jurassic period. "Sapheosaurs" is an informal name for a group of rhynchocephalians closely related to the genus Sapheosaurus. It was first recognized as a group containing multiple genera by Hoffstetter in 1955. The group has sometimes been given a formal taxonomic name as the family Sapheosauridae, although in some analyses this group belongs to the family Sphenodontidae and thus cannot be assigned its own family. They were fairly advanced rhynchocephalians which may have had semiaquatic habits.
Fraxinisaura is an extinct genus of basal lepidosauromorph reptile known from the Middle Triassic of Germany. The only known species is Fraxinisaura rozynekae. It possessed an elongated snout, unique features of the teeth, and an ilium which was intermediate in orientation between sphenodontians and squamates. Based on characteristics of the maxilla, it is considered a close relative of Marmoretta from the Middle Jurassic of the United Kingdom, resolving a ghost lineage between that genus and other Triassic basal lepidosauromorphs.
Eilenodontinae are an extinct clade of reptiles belonging to Sphenodontia. They are either considered a subgroup of Opisthodontia, or Sphenodontidae. They had deep jaws with broad, closely packed teeth with thick enamel and noticeable wear facets. They were likely herbivorous, and probably chewed with a proal movement, with food shredded between the edges of opposing sharp-edged wear facets. Members of the group are known from South America, North America and Europe. The earliest known member of the group, Sphenotitan, is known from the Late Triassic of South America. while the youngest members are known from the Late Cretaceous of South America. The group contains some of the largest known sphenodontians, with Priosphenodon suggested to be the largest known non aquatic sphenodontian, with an estimated body length of over 1 metre (3.3 ft).
Bonacynodon is an extinct genus of cynodonts that lived in what is now southern Brazil during the Triassic period. The genus is monotypic, containing only the type species Bonacynodon schultzi. B. schultzi is known from two specimens, consisting of two partial skulls and some badly preserved parts of the postcranium. Both specimens were recovered from the Pinheiros-Chiniquá Sequence, part of the Santa Maria Supersequence of the Paraná Basin. This sequence preserves a faunal association known as the Dinodontosaurus Assemblage Zone, which contains numerous other species of cynodonts, dicynodonts and reptiles. Bonacynodon was a small, likely insectivorous cynodont, whose length has been estimated at around 30 centimetres (12 in). It can be distinguished from other cynodonts by its large, serrated (saw-like) canine teeth. Together with the genus Probainognathus of Argentina, it made up the family Probainognathidae, one of the earliest-diverging lineages of the clade Probainognathia. It was a fairly close relative of mammals, the only group of cynodonts alive today.
Pachagnathus is an extinct genus of non-pterodactyloid pterosaur from the late Norian–early Rhaetian-aged Quebrada del Barro Formation of Argentina. It lived in the Late Triassic period, and is one of the only known definitive Triassic pterosaurs from the southern hemisphere. It is also one of the few known continental Triassic pterosaurs, indicating that the absence of early pterosaurs in both the southern hemisphere and terrestrial environments is likely a sampling bias, and not a true absence.
Yelaphomte is an extinct genus of non-pterodactyloid pterosaur from the late Norian–early Rhaetian-aged Quebrada del Barro Formation of Argentina. It lived in the Late Triassic period, and is one of the only known definitive Triassic pterosaurs from the southern hemisphere. It was a small and crested pterosaur, although its small size may be due to immaturity. It is also one of the few known continental Triassic pterosaurs, indicating that the absence of early pterosaurs in both the southern hemisphere and terrestrial environments is likely a sampling bias, and not a true absence.
