Cladoselache is an extinct genus of shark-like chondrichthyan from the Late Devonian (Famennian) of North America. It was similar in body shape to modern lamnid sharks, but was not closely related to lamnids or to any other modern (selachian) shark. As an early chondrichthyan, it had yet to evolve traits of modern sharks such as accelerated tooth replacement, a loose jaw suspension, enameloid teeth, and possibly claspers.
Orthacanthus is an extinct genus of fresh-water xenacanthiform cartilaginous fish, named by Louis Agassiz in 1843, ranging from the Upper Carboniferous into the Lower Permian. Orthacanthus had a nektobenthic life habitat, with a carnivorous diet. Multiple authors have also discovered evidence of cannibalism in the diet of Orthacanthus and of "filial cannibalism" where adult Orthacanthus preyed upon juvenile Orthacanthus. Synonyms of the genus Orthacanthus are Dittodus Owen, 1867, Didymodus Cope, 1883, Diplodus Agassiz, 1843, Chilodus Giebel, 1848.
Helicoprion is an extinct genus of shark-like eugeneodont fish. Almost all fossil specimens are of spirally arranged clusters of the individuals' teeth, called "tooth whorls", which in life were embedded in the lower jaw. As with most extinct cartilaginous fish, the skeleton is mostly unknown. Fossils of Helicoprion are known from a 20 million year timespan during the Permian period from the Artinskian stage of the Cisuralian to the Roadian stage of the Guadalupian. The closest living relatives of Helicoprion are the chimaeras, though their relationship is very distant. The unusual tooth arrangement is thought to have been an adaption for feeding on soft bodied prey, and may have functioned as a deshelling mechanism for hard bodied cephalopods such as nautiloids and ammonoids. In 2013, systematic revision of Helicoprion via morphometric analysis of the tooth whorls found only H. davisii, H. bessonowi and H. ergassaminon to be valid, with some of the larger tooth whorls being outliers.
Xenacanthida is an order or superorder of extinct shark-like chondrichthyans known from the Carboniferous to Triassic. They were native to freshwater, marginal marine and shallow marine habitats. Some xenacanths may have grown to lengths of 5 m (16 ft). Most xenacanths died out at the end of the Permian in the End-Permian Mass Extinction, with only a few forms surviving into the Triassic.
Hybodus is an extinct genus of hybodont that lived from the Middle Triassic to the Late Cretaceous periods. Species closely related to the type species Hybodus reticulatus lived during the Early Jurassic epoch. Numerous species have been assigned to Hybodus spanning a large period of time, and it is currently considered a wastebasket taxon that is 'broadly polyphyletic' and requires reexamination.
Angelosaurus is an extinct genus of herbivorous caseid synapsids that lived during the late Lower Permian (Kungurian) and early Middle Permian (Roadian) in what is now Texas and Oklahoma. Like other herbivorous caseids, it had a small head, large barrel-shaped body, long tail, and massive limbs. Angelosaurus differs from other caseids by the extreme massiveness of its bones, particularly those of the limbs, which show a strong development of ridges, processes, and rugosities for the attachment of muscles and tendons. Relative to its body size, the limbs of Angelosaurus were shorter and wider than those of other caseids. The ungual phalanges looked more like hooves than claws. The few known cranial elements show that the skull was short and more robust than that of the other representatives of the group. Angelosaurus is also distinguished by its bulbous teeth with shorter and wider crowns than those of other caseids. Their morphology and the high rate of wear they exhibit suggests a diet quite different from that of other large herbivorous caseids, and must have been based on particularly tough plants. A study published in 2022 suggests that the genus may be paraphyletic, with Angelosaurus possibly only represented by its type species A. dolani.
Fadenia is an extinct genus of eugeneodontid holocephalian chondrichthyan from the Carboniferous Period of Missouri, the Permian period of Greenland, and the Early Triassic epoch of British Columbia, Canada.
Hybodontiformes, commonly called hybodonts, are an extinct group of shark-like cartilaginous fish (chondrichthyans) which existed from the late Devonian to the Late Cretaceous. Hybodonts share a close common ancestry with modern sharks and rays (Neoselachii) as part of the clade Euselachii. They are distinguished from other chondrichthyans by their distinctive fin spines and cephalic spines present on the heads of males. An ecologically diverse group, they were abundant in marine and freshwater environments during the late Paleozoic and early Mesozoic, but were rare in open marine environments by the end of the Jurassic, having been largely replaced by modern sharks, though they were still common in freshwater and marginal marine habitats. They survived until the end of the Cretaceous, before going extinct.
Xiongguanlong is an extinct genus of tyrannosauroid theropod from the Early Cretaceous period of what is now China. The type and only species is X. baimoensis. The generic name comes from Jiayuguan City and the Mandarin word "long" which means dragon. The specific epithet, "baimoensis" is a latinization of the Mandarin word for "white ghost" in reference to one of the geological features of the type locality.
Cladistia is a clade of bony fishes whose only living members are the bichirs of tropical Africa. Their major synapomorphies are a heterocercal tail in which the dorsal fin has independent rays, and a posteriorly elongated parasphenoid.
Beishanichthys is an extinct genus of freshwater ray-finned fish which existed in Gansu Province, China during the Olenekian age of the early Triassic period. It contains a single species, B. brevicaudalis, first named by Guang-Hui Xu, Ke-Qin Gao in 2011 based on fossils from the Lower Triassic lake deposits exposed in northern Gansu, China. It is considered a scanilepiform, a group of early cladistians related to the modern bichirs, although Beishanichthys was not incorporated into the analyses that found this phylogenetic placement among the cladistians.
Plicatodus is a prehistoric cartilaginous fish in the family Xenacanthidae that lived in Europe during the late Carboniferous and Early Permian Periods. It was described by Oliver Hampe in 1995, and the type species is Plicatodus jordani. The type locality for this genus is the Saar-Nahe basin.
Antarctilamna is an extinct genus of Devonian cartilaginous fish originally exemplified by Antarctilamna prisca from South Eastern Australia and Antarctica. The latest occurring described species is Antarctilamna ultima from the Waterloo Farm lagerstätte in South Africa. Antarctilamna has robust ctenacanthid-like spines which lack a deep insertion area, and are borne in front of the first dorsal fin; in addition to distinctive diplodont teeth with small intermediate cusps. Antarctilamna-like spines, known from the Bunga Beds locality in Australia have been ascribed to A. prisca.
Cricodon is an extinct genus of trirachodontid cynodonts that lived during the Early Triassic and Middle Triassic periods of Africa. A. W. Crompton named Cricodon based on the ring-like arrangement of the cuspules on the crown of a typical postcanine tooth. The epithet of the type species, C. metabolus, indicates the change in structure of certain postcanines resulting from replacement.
Arisierpeton is an extinct genus of synapsids from the Early Permian Garber Formation of Richards Spur, Oklahoma. It contains a single species, Arisierpeton simplex.
Cretacladoides is a genus of chondrichthyan, possibly a falcatid, found in France and Austria. Known solely from teeth, mainly found in the Klausrieglerbach locality of Austria, it consists of two species, C. ogiveformis and C. noricum. Assuming a falcatid identity, it is the most recent member of the family, which otherwise became extinct at the end of the Carboniferous.
Dracopristis is an extinct genus of ctenacanth that lived during the Carboniferous period in North America, around 307 million years ago. The species was discovered in the Kinney Brick Quarry in New Mexico, US. Like many fossils from the site, the fossils of Dracopristis are very well-preserved. A single species is known, Dracopristis hoffmanorum, which is named in honor of Ralph and Jeanette Hoffman, the owners of the quarry. Prior to being scientific named, D. hoffmanorum was informally referred to as the "Godzilla shark".
Baiyinosaurus is an extinct genus of stegosaurian dinosaurs from the Middle Jurassic Wangjiashan Formation of China. The genus contains a single species, B. baojiensis, known from a partial skeleton including cranial bones. The skeletal anatomy of Baiyinosaurus demonstrates transitional features between basal thyreophorans and stegosaurs. While many stegosaurs are known from China, Baiyinosaurus is the only one currently named from Gansu Province.
Paredestus is a monotypic genus of extinct eugeneodont holocephalan from the Early Triassic of Canada. The type and only species, P. bricircum represents the last known member of the superfamily Edestoidea and among the last known eugeneodonts. It was named in 2008 based on tooth and jaw material, with the holotype representing the only known specimen.
Tanaocrossus is an extinct genus of primitive freshwater ray-finned fish that inhabited southwestern and eastern North America during the Late Triassic period. It contains a single known species, T. kalliokoskii, known from the United States, with indeterminate species also known.
