Chondrichthyes is a class of jawed fish that contains the cartilaginous fish or chondrichthyians, which all have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or bony fish, which have skeletons primarily composed of bone tissue. Chondrichthyes are aquatic vertebrates with paired fins, paired nares, placoid scales, conus arteriosus in the heart, and a lack of opecula and swim bladders. Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates.
Chimaeras are cartilaginous fish in the order Chimaeriformes, known informally as ghost sharks, rat fish, spookfish, or rabbit fish; the last three names are not to be confused with rattails, Opisthoproctidae, or Siganidae, respectively.
Cow sharks are a shark family, the Hexanchidae, characterized by an additional pair or pairs of gill slits. Its 37 species are placed within the 10 genera: Gladioserratus, Heptranchias, Hexanchus, Notidanodon, Notorynchus, Pachyhexanchus, Paraheptranchias, Pseudonotidanus, Welcommia, and Weltonia.
Holocephali, sometimes given the term Euchondrocephali, is a subclass of cartilaginous fish in the class Chondrichthyes. The earliest fossils are of teeth and come from the Devonian period. Little is known about these primitive forms, and the only surviving group in the subclass is the order Chimaeriformes.
Stethacanthus is an extinct genus of shark-like holocephalians which lived from the Late Devonian to Late Carboniferous epoch, dying out around 298.9 million years ago. Fossils have been found in Australia, Asia, Europe and North America.
Ischyodus is an extinct genus of chimaera. It is the most diverse and long-lived chimaera genus, with over 39 species found worldwide spanning over 140 million years from the Middle Jurassic to the Miocene. Complete specimens of I. quenstedti from the Late Jurassic of Germany most closely resemble the genus Callorhinchus amongst living chimaera genera. It is sometimes placed in the "Edaphodontidae" a unclearly defined group of chimaera with an uncertain position within the clade. While other authors place it into Callorhinchidae along with Callorhinchus.
Edaphodon kawai was a prehistoric chimaeriform fish species belonging to the genus Edaphodon, of which all the species are now extinct. Edaphodon kawai was a type of rabbitfish, a cartilaginous fish related to sharks and rays, and indeed, some rabbitfishes are still alive today. E. kawai is one of numerous Edaphodon species, but is the only one which has been discovered in the Southern Hemisphere, near New Zealand. Indeed, only a handful of other Chimaeroformes have been discovered in the Southern Hemisphere. They first appeared during the Devonian period around 415 to 360 million years ago, but the only known specimen of E. kawai has been dated to the Late Cretaceous at the height of the rabbitfish's reign. Its scientific name, kawai, means "fish" in the language of the Moriori, a Pacific tribe who inhabited the islands.
Symmoriiformes is an extinct order of stem-group holocephalians. Originally named Symmoriida by Zangerl (1981), it has subsequently been known by several other names. Lund (1986) synonymized the group with Cladodontida, while Maisey (2008) corrected the name to Symmoriiformes in order to prevent it from being mistaken for a family. The symmoriiform fossils record begins during the late Devonian. Most of them died out at the start of the Permian, but Dwykaselachus is known from the Artinskian-Kungurian of South Africa. Teeth described from the Valanginian of France and Austria indicate that members of the family Falcatidae might have survived until the Early Cretaceous; however, these teeth were also argued to be more likely neoselachian teeth.
Falcatus is an extinct genus of falcatid chondrichthyan which lived during the early Carboniferous Period in Bear Gulch bay in what is now Montana.
Hydrolagus is a genus of fish in the family Chimaeridae found in the Atlantic, Indian and Pacific Oceans.
Ptychodus is a genus of extinct durophagous (shell-crushing) sharks from the Late Cretaceous. Fossils of Ptychodus teeth are found in many Late Cretaceous marine sediments. There are many species among the Ptychodus that have been uncovered on all the continents around the globe. Such species are Ptychodus mortoni, P. decurrens, P. marginalis, P. mammillaris, P. rugosus and P. latissimus to name a few. They died out approximately 85 million years ago. A large number of remains have been found in the former Western Interior Seaway. A 2016 publication found that Ptychodus are likely true sharks belonging to Selachimorpha, rather than hybodonts or batoids as previously thought. Their life history coincides with the typical life of many other large sharks: they lived relatively long lives and were slow growing and produced large offspring and small litters.
Chimaera is the type genus of the cartilaginous fish family Chimaeridae.
Chondrenchelys is an extinct genus of cartilaginous fish and the earliest member of Holocephali known from complete skeletons. Chondrenchelys would have been quite a relatively medium-sized fish with an elongated body up to 18 cm (0.59 ft)in length, it had a dorsal fin which was indeed long and a body which tapered to a point. Chondrenchelys had one large pair, one middle-sized pair, and three small pair of tooth plates in each jaw.
Ptychoceratodus is an extinct genus of lungfish living from Early Triassic to Middle Jurassic. It was established by Otto Jaekel for one species, transferred from Ceratodus genus. Type species is P. serratus from the Middle Triassic of Switzerland and Germany. Ptychoceratodus had two pairs of massive dental plates, bearing 4-6 acute ridges. Its skull roof was composed from massive, plate-like bones. In the central part of skull roof was localized an unossified fenestra. Most of the Ptychoceratodus findings are isolated dental plates, some associated with jaws. Other parts of skull or postcranial skeleton are relatively rarely found as fossils. The anatomy of skull is the best recognized in P. serratus, whereas less complete cranial material is available also for P. concinuus, P. phillipsi, and P. rectangulus. Although Ptychoceratodus is known exclusively from the Triassic and Jurassic, there were also Cretaceous specimens referred to this genus. However, they are more often regarded as representants of Metaceratodus. Ptychoceratodus is the only member of the family Ptychoceratodontidae. The first named species is P. phillipsi by Louis Agassiz in 1837 as a species of Ceratodus and later moved to Ptychoceratodus genus. Occurrences of Ptychoceratodus come mainly from Europe. However, occurrences from other continents suggest it was dispersed globally during the Triassic. After 2010, the new fossil material behind the Europe was reported from South America, India, and Greenland
The Snow Hill Island Formation is an Early Maastrichtian geologic formation found on James Ross Island, James Ross Island group, Antarctica. Remains of a paravian theropod Imperobator antarcticus have been recovered from it, as well as the elasmarian ornithopods Trinisaura santamartaensis, Biscoveosaurus and Morrosaurus antarcticus, the ankylosaurian Antarctopelta oliveroi, and the shark Notidanodon sp. Alongside these described genera are also the remains of indeterminate elasmosaurids, lithostrotian titanosaurs and an indeterminate pterosaur.
The New Egypt Formation is a Late Cretaceous (Maastrichtian) geologic formation of the Monmouth Group in New Jersey, United States.
Ptyctodus is an extinct armour-plated fish of the late Devonian. Ptyctodus belongs to the family Ptyctodontidae and is of the class Placodermi. They share a close resemblance to modern day chimaeras (Holocephali). Fossils of this armour-plated fish have been found in locations such as in Russia, the Michigan Basis, and Arizona, United States.
Amylodon is an extinct genus of chimaera. It consists of four described species. A. karamysh is known from the latest early Campanian of Russia, the name being derived from the Karamysh River which runs near the type locality. In the Eocene, two species are known. A. venablesae and A. eocenica are both known from the Ypresian-aged London Clay of England. A mandibular plate originally ascribed to the latter was found in the Bartonian of the Barton Beds of England, though later found not to fit with any described species. A. delheidi is known from the Rupelian-aged Boom Clay of Belgium. All species are known mainly from isolated mandibles. They show a slow progressing towards increased shearing ability. Amylodon was considered to be a member of Chimaeridae in Nessov and Averianov, 1996 but other studies have either been assigned to the "Edaphodontidae", or to the Rhinochimaeridae.
Pachymylus is an extinct genus of chimaera belonging to the family Callorhynchidae. The type species. P. leedsi was described by A. S. Woodward in 1892, and is known from the Middle-Late Jurassic (Callovian-Oxfordian) Oxford Clay of Peterborough, England. The type material consisted of a large mandibular tooth and two palatine teeth. Indeterminate remains of the genus are also known from the Middle Jurassic (Bajocian) of France.
