Herrerasauridae is a family of carnivorous dinosaurs, possibly basal to either theropods or even all of saurischians, or even their own branching from Dracohors, separate from Dinosauria altogether. They are among the oldest known dinosaurs, first appearing in the fossil record around 233.23 million years ago, before becoming extinct by the end of the Carnian stage. Herrerasaurids were relatively small-sized dinosaurs, normally no more than 4 metres (13 ft) long, although the holotype specimen of "Frenguellisaurus ischigualastensis" is thought to have reached around 6 meters long. The best known representatives of this group are from South America, where they were first discovered in the 1930s in relation to Staurikosaurus and 1960s in relation to Herrerasaurus. A nearly complete skeleton of Herrerasaurus ischigualastensis was discovered in the Ischigualasto Formation in San Juan, Argentina, in 1988. Less complete possible herrerasaurids have been found in North America and Africa, and they may have inhabited other continents as well.
Crurotarsi is a clade of archosauriform reptiles that includes crocodilians and stem-crocodilians and possibly bird-line archosaurs too if the extinct, crocodile-like phytosaurs are more distantly related to crocodiles than traditionally thought. Prior to 2011, the group had invariably included only archosaurs closer to crocodilians than to birds and other dinosaurs. An equivalent term for the crocodilian side of the archosaur family tree is Pseudosuchia. This traditional definition of Crurotarsi assumed that phytosaurs were crown-group archosaurs and more closely related to crocodilians than to birds. However, a 2011 study argued that the phytosaur lineage evolved prior to the split between birds and crocodilians. This would mean that phytosaurs were not true archosaurs, and therefore could not be considered representatives of croc-line archosaurs.
"Rauisuchia" is a paraphyletic group of mostly large and carnivorous Triassic archosaurs. Rauisuchians are a category of archosaurs within a larger group called Pseudosuchia, which encompasses all archosaurs more closely related to crocodilians than to birds and other dinosaurs. First named in the 1940s, Rauisuchia was a name exclusive to Triassic archosaurs which were generally large, carnivorous, and quadrupedal with a pillar-erect hip posture, though exceptions exist for all of these traits. Rauisuchians, as a traditional taxonomic group, were considered distinct from other Triassic archosaur groups such as early dinosaurs, phytosaurs, aetosaurs, and crocodylomorphs.
Effigia was an extinct genus of shuvosaurid known from the Late Triassic of New Mexico, south-western USA. With a bipedal stance, long neck, and a toothless beaked skull, Effigia and other shuvosaurids bore a resemblance to the ornithomimid dinosaurs of the Cretaceous Period. However, shuvosaurids were not dinosaurs, but were instead a specialized family of poposauroid pseudosuchians, meaning that their closest living relatives are crocodilians.
Shuvosaurus is a genus of beaked reptile from the Late Triassic of western Texas. Despite looking superficially similar to a theropod dinosaur, it is actually more closely related to crocodilians.
Spinosuchus is an extinct genus of trilophosaurid allokotosaur from the Late Triassic of Texas, southern United States. It has been assigned to a variety of groups over its history, from coelophysid dinosaur to pseudosuchian to uncertain theropod dinosaur and to Proterosuchidae. This uncertainty is not unusual, given that it was only known from a poorly preserved, wall-mounted, partial vertebral column of an animal that lived in a time of diverse, poorly known reptile groups. However, newly collected material and recent phylogenetic studies of early archosauromorphs suggest that it represents an advanced trilophosaurid very closely related to Trilophosaurus.
Prestosuchidae is a polyphyletic grouping of carnivorous archosaurs that lived during the Triassic. They were large active terrestrial apex predators, ranging from around 2.5 to 7 metres in length. They succeeded the Erythrosuchidae as the largest archosaurs of their time. While resembling erythrosuchids in size and some features of the skull and skeleton, they were more advanced in their erect posture and crocodile-like ankle, indicating more efficient gait. "Prestosuchids" flourished throughout the whole of the middle, and the early part of the late Triassic, and fossils are so far known from Europe, India, Africa (Tanzania), Argentina, and Paleorrota in Brazil. However, for a long time experts disagree regarding the phylogenetic relationships of the group, what genera should be included, and whether indeed the "Prestosuchidae" constitute a distinct family.
Dinosauromorpha is a clade of avemetatarsalian archosaurs 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.
Parasuchus is an extinct genus of basal phytosaur known from the Late Triassic of Andhra Pradesh and Madhya Pradesh, India. At its most restricted definition, Parasuchus contains a single species, Parasuchus hislopi. Parasuchus hislopi is one of several species belonging to a basal grade of phytosaurs, typified by the genus Paleorhinus. Historically, Paleorhinus has been known from better-described fossils, and many species have been lumped into that genus. Parasuchus hislopi, despite being described earlier than Paleorhinus, was considered an undiagnostic chimera until new neotype fossils were described in the late 1970s. Parasuchus hislopi and the two unambiguously valid species of Paleorhinus are all closely related; some authors have historically described them all under the species Paleorhinus, while others place the two Paleorhinus species into Parasuchus according to the principle of priority.
Lotosaurus is an extinct genus of sail-backed poposauroid known from Hunan Province of central China.
Ornithosuchidae is an extinct family of pseudosuchian archosaurs from the Triassic period. Ornithosuchids were quadrupedal and facultatively bipedal, meaning that they had the ability to walk on two legs for short periods of time. They had distinctive, downturned snouts, unique, "crocodile-reversed" ankle bones, and several other features that distinguish them from other archosaurs. Ornithosuchids were geographically widespread during the Carnian and Norian stages of the Late Triassic with members known from Argentina, Brazil, and the United Kingdom. Four genera, comprising Ornithosuchus, Venaticosuchus, Dynamosuchus, and Riojasuchus are presently known. The family was first erected by German paleontologist Friedrich von Huene in 1908.
Ctenosauriscidae is an extinct family of pseudosuchian archosaurs within the clade Poposauroidea. Ctenosauriscids existed in Africa, Asia, Europe and North America during the Early Triassic to the Middle Triassic period. All species had large "sails" on their backs. Ctenosauriscids are among some of the earliest archosaurs and represent the first global radiation of the group.
Malerisaurus is an extinct genus of archosauromorph known from Andhra Pradesh of India and Texas of the USA.
Sillosuchus is a genus of shuvosaurid poposauroid archosaur that lived in South America during the Late Triassic period. Shuvosaurids were an unusual family of reptiles belonging to the group Poposauroidea; although their closest modern relatives are crocodilians, they were bipedal and lightly armored, with dinosaur-like hip and skull structures. Based on skull remains from members of the family such as Effigia, they were also toothless and likely beaked herbivores.
Yarasuchus is an extinct genus of avemetatarsalian archosaur that lived during the Anisian stage of the Middle Triassic of India. The genus was named and described in 2005 from a collection of disarticulated but fairly complete fossil material found from the Middle Triassic Yerrapalli Formation. The material is thought to be from two individuals, possibly three, with one being much more complete and articulated than the other. The type and only species is Y. deccanensis. Yarasuchus was a quadruped roughly 2–2.5 metres (6.6–8.2 ft) long, with an elongated neck and tall spines on its vertebrae. Unlike other quadrupedal Triassic reptiles, the limbs and shoulders of Yarasuchus were slender, and more like those of ornithodirans.
Fasolasuchus is an extinct genus of loricatan. Fossils have been found in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina that date back to the Norian stage of the Late Triassic, making it one of the last "rauisuchians" to have existed before the order became extinct at the end of the Triassic.
Poposauroidea is a clade of advanced pseudosuchians. It includes poposaurids, shuvosaurids, ctenosauriscids, and other unusual pseudosuchians such as Qianosuchus and Lotosaurus. However, it excludes most large predatory quadrupedal "rauisuchians" such as rauisuchids and "prestosuchids". Those reptiles are now allied with crocodylomorphs in a clade known as Loricata, which is the sister taxon to the poposauroids in the clade Paracrocodylomorpha. Although it was first formally defined in 2007, the name "Poposauroidea" has been used for many years. The group has been referred to as Poposauridae by some authors, although this name is often used more narrowly to refer to the family that includes Poposaurus and its close relatives.
Epipophyses are bony projections of the cervical vertebrae found in archosauromorphs, particularly dinosaurs. These paired processes sit above the postzygapophyses on the rear of the vertebral neural arch. Their morphology is variable and ranges from small, simple, hill-like elevations to large, complex, winglike projections. Epipophyses provided large attachment areas for several neck muscles; large epipophyses are therefore indicative of a strong neck musculature.
The Colorado City Formation is a Late Triassic geologic formation in the Dockum Group of Texas, United States. It has previously been known as the Iatan Member, Colorado City Member or 'Pre-Tecovas Horizon'.
Vivaron is a genus of rauisuchid known from the Late Triassic Chinle Formation in New Mexico. It is the second rauisuchid known from the southwestern United States, and it highlights the wide biogeographic range similar rauisuchid taxa occupied during the Late Triassic across Pangaea, despite the varied faunal assemblages at different latitudes.
