The Triassic is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.9 million years ago (Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic Period is subdivided into three epochs: Early Triassic, Middle Triassic and Late Triassic.
Archosauriformes is a clade of diapsid reptiles that developed from archosauromorph ancestors some time in the Latest Permian. It was defined by Jacques Gauthier (1994) as the clade stemming from the last common ancestor of Proterosuchidae and Archosauria ; Phil Senter (2005) defined it as the most exclusive clade containing Proterosuchus and Archosauria.
Phytosaurs are an extinct group of large, mostly semiaquatic Late Triassic archosauriform reptiles. Phytosaurs belong to the order Phytosauria. and are sometimes referred to as parasuchians. Phytosauria, Parasuchia, Parasuchidae, and Phytosauridae have often been considered equivalent groupings containing the same species. Some recent studies have offered a more nuanced approach, defining Parasuchidae and Phytosauridae as nested clades within Phytosauria as a whole. Phytosaurs were long-snouted and heavily armoured, bearing a remarkable resemblance to modern crocodilians in size, appearance, and lifestyle, as an example of convergence or parallel evolution. The name "phytosaur" means "plant reptile", as the first fossils of phytosaurs were mistakenly thought to belong to plant eaters.
Aetosaurs are heavily armored reptiles belonging to the extinct order Aetosauria. They were medium- to large-sized omnivorous or herbivorous pseudosuchians, part of the branch of archosaurs more closely related to crocodilians than to birds and other dinosaurs. All known aetosaurs are restricted to the Late Triassic, and in some strata from this time they are among the most abundant fossil vertebrates. They have small heads, upturned snouts, erect limbs, and a body ornamented with four rows of plate-like osteoderms. Aetosaur fossil remains are known from Europe, North and South America, parts of Africa, and India. Since their armoured plates are often preserved and are abundant in certain localities, aetosaurs serve as important Late Triassic tetrapod index fossils. Many aetosaurs had wide geographic ranges, but their stratigraphic ranges were relatively short. Therefore, the presence of particular aetosaurs can accurately date a site in which they are found.
Arizonasaurus was a ctenosauriscid archosaur from the Middle Triassic. Arizonasaurus is found in the Middle Triassic Moenkopi Formation of northern Arizona. A fairly complete skeleton was found in 2002 by Sterling Nesbitt. The taxon has a large sailback formed by elongated neural spines of the vertebrae. The type species, Arizonasaurus babbitti, was named by Samuel Paul Welles in 1947.
Rhynchosaurs are a group of extinct herbivorous Triassic archosauromorph reptiles, belonging to the order Rhynchosauria. Members of the group are distinguished by their triangular skulls and elongated, beak like premaxillary bones. Rhynchosaurs first appeared in the Middle Triassic or possibly the Early Triassic, before becoming abundant and globally distributed during the Carnian stage of the Late Triassic.
Erythrosuchidae are a family of large basal archosauriform carnivores that lived from the later Early Triassic (Olenekian) to the early Middle Triassic (Anisian).
Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction.
Hindeodus is an extinct genus of conodonts in the family Anchignathodontidae. The generic name Hindeodus is a tribute to George Jennings Hinde, a British geologist and paleontologist from the 1800s and early 1900s. The suffix -odus typically describes the animal's teeth, essentially making Hindeodus mean Hinde-teeth.
Proterochampsidae is a family of proterochampsian archosauriforms. Proterochampsids may have filled an ecological niche similar to modern crocodiles, and had a general crocodile-like appearance. They lived in what is now South America in the Middle and Late Triassic.
Moschorhinus is an extinct genus of therocephalian in the family Akidnognathidae with only one species: M. kitchingi. It was a carnivorous synapsid which has been found in the Late Permian to Early Triassic of the South African Karoo Supergroup. It was a large carnivore, reaching 1.5 m (4.9 ft) in total body length with the largest skull comparable to that of a lion in size. It had a broad, blunt snout which bore long, straight canines. It appears to have replaced the gorgonopsids ecologically, and hunted much like a big cat. While most abundant in the Late Permian, it survived a little after the Permian Extinction, though these Triassic individuals had stunted growth.
Stereospondylomorpha is a clade of temnospondyls. It includes the superfamily Archegosauroidea and the more diverse group Stereospondyli. Stereospondylomorpha was first proposed by Yates and Warren (2000), who found Archegosauroidea and Stereospondyli to be sister taxa in their phylogenetic analysis. A similar clade is Archegosauriformes, named by Schoch and Milner (2000), which includes Stereospondyli and some Permian temnospondyls that are similar in appearance to stereospondyls, including the archegosauroids. However, according to Schoch and Milner's phylogeny, Archegosauroidea is a paraphyletic group of taxa that are successively basal to Stereospondyli, rather than a monophyletic sister taxon.
Kuehneosauridae is an extinct family of small, lizard-like gliding diapsids known from the Triassic period of Europe and North America. They are distinguished from other diapsids by their 'wings' formed by elongated ribs. These allowed the animal to glide and parachute similar to living gliding lizards. They were most likely insectivorous, judging from their pin-like teeth. They are often, but not always, placed in the group Lepidosauromorpha, though other studies have recovered them in other positions within Sauria, including Archosauromorpha. The oldest and most primitive known member is Pamelina from the Early Triassic of Poland, which already has vertebrae with characteristics consistent with gliding or parachuting. Icarosaurus is known from a single specimen from the Carnian-aged Lockatong Formation of New Jersey. The Late Triassic kuehneosaurids from England, Kuehneosaurus and Kuehneosuchus, are very similar and can be distinguished from one another primarily on the length of their "wing" ribs, relatively short and massive in Kuehneosaurus but longer and more gracile in Kuehneosuchus. Kuehneosaurus was likely only capable of parachuting, while Kuehneosuchus could probably glide. Rhabdopelix may have been a kuehneosaurid; however, the fossils were lost, and the characteristics described are not entirely consistent with the other family members.
Lumkuia is an extinct genus of cynodonts, fossils of which have been found in the Cynognathus Assemblage Zone of the Beaufort Group in the South African Karoo Basin that date back to the early Middle Triassic. It contains a single species, Lumkuia fuzzi, which was named in 2001 on the basis of the holotype specimen BP/1/2669, which can now be found at the Bernard Price Institute in Johannesburg, South Africa. The genus has been placed in its own family, Lumkuiidae. Lumkuia is not as common as other cynodonts from the same locality such as Diademodon and Trirachodon.
Leptosuchus is an extinct genus of leptosuchomorph phytosaur with a complex taxonomical history. Fossils have been found from the Dockum Group and lower Chinle Formation outcropping in Texas, New Mexico, and Arizona, USA, and date back to the Carnian stage of the Late Triassic.
Uatchitodon is an extinct genus of Late Triassic reptile known only from isolated teeth. Based on the structure of the teeth, Uatchitodon was probably a carnivorous archosauromorph. Folded grooves on the teeth indicate that the animal was likely venomous, with the grooves being channels for salivary venom. The teeth are similar to those of living venomous squamates such as Heloderma and venomous snakes. Uatchitodon is the earliest known venomous reptile.
Loricata is a clade of archosaur reptiles that includes crocodilians and some of their Triassic relatives, such as Postosuchus and Prestosuchus. More specifically, Loricata includes Crocodylomorpha and most "rauisuchians", a paraphyletic grade of large terrestrial pseudosuchians which were alive in the Triassic period and ancestral to crocodylomorphs.
Doswelliidae is an extinct family of carnivorous archosauriform reptiles that lived in North America and Europe during the Middle to Late Triassic period. Long represented solely by the heavily-armored reptile Doswellia, the family's composition has expanded since 2011, although two supposed South American doswelliids were later redescribed as erpetosuchids. Doswelliids were not true archosaurs, but they were close relatives and some studies have considered them among the most derived non-archosaurian archosauriforms. They may have also been related to the Proterochampsidae, a South American family of crocodile-like archosauriforms.
Callaionautilus is a genus of cephalopods included in the nautilid family Clydonautilidae that lived during the Late Triassic. Its fossils have been found on the island of Timor.
Azendohsauridae is a family of allokotosaurian archosauromorphs that lived during the Middle to Late Triassic period, around 242-216 million years ago. The family was originally named solely for the eponymous Azendohsaurus, marking out its distinctiveness from other allokotosaurs, but as of 2022 the family now includes four other genera: the basal genus Pamelaria, the large horned herbivore Shringasaurus, and two carnivorous genera grouped into the subfamily-level subclade Malerisaurinae, Malerisaurus and Puercosuchus, and potentially also the dubious genus Otischalkia. Most fossils of azendohsaurids have a Gondwanan distribution, with multiple species known across Morocco and Madagascar in Africa as well as India, although fossils of malerisaurine azendohsaurids have also been found in the southwestern United States of North America.
