Coelacanths are an ancient group of lobe-finned fish (Sarcopterygii) in the class Actinistia. As sarcopterygians, they are more closely related to lungfish and tetrapods than to ray-finned fish.
The Amiiformes order of fish has only two extant species, the bowfins: Amia calva and Amia ocellicauda, the latter recognized as a separate species in 2022. These Amiiformes are found in the freshwater systems of North America, in the United States and parts of southern Canada. They live in freshwater streams, rivers, and swamps. The order first appeared in the Triassic, and the extinct members include both marine and freshwater species, many of which are morphologically disparate from bowfins, such as the caturids.
Hybodus is an extinct genus of hybodont, a group of shark-like euselachians that lived from the Late Devonian to the end of the Cretaceous. 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.
Lepidotes is an extinct genus of Mesozoic ray-finned fish. It has long been considered a wastebasket taxon, characterised by "general features, such as thick rhomboid scales and, for most of the species, by semi-tritorial or strongly tritorial dentition". with dozens of species assigned to it. Fossils attributed to Lepidotes have been found in Jurassic and Cretaceous rocks worldwide. It has been argued that Lepidotes should be restricted to species closely related to the type species L. gigas, which are only known from the Early Jurassic of Western and Central Europe, with most other species being not closely related, with other species transferred to new genera such as Scheenstia.Lepidotes belongs to Ginglymodi, a clade of fish whose only living representatives are the gars (Lepisosteidae). The type species L. gigas and close relatives are thought to be members of the family Lepidotidae, part of the order Lepisosteiformes within Ginglymodi, with other species occupying various other positions within Ginglymodi.
Chinlea is an extinct genus of late Triassic Mawsoniid coelacanth fish found in and named after the Chinle Formation that crops out in the southwestern states of Arizona and New Mexico. The word “Chinle” comes from the Navajo word meaning "flowing out", referencing the location where water flows out of the Canyon de Chelly. They were also possibly found in the Dockum Group.
Latimeriidae is the only extant family of coelacanths, an ancient lineage of lobe-finned fish. It contains two extant species in the genus Latimeria, found in deep waters off the coasts of southern Africa and east-central Indonesia. In addition, several fossil genera are known from the Mesozoic of Europe, the Middle East, and the southeastern United States, dating back to the Triassic.
Lycoptera is an extinct genus of fish that lived from Lower Cretaceous, Barremian to Aptian in present-day China, North Korea, Mongolia and Siberia. Although there is record from Jurassic Formation in Siberia, its age remains questionable. It is known from abundant fossils representing sixteen species, which serve as important index fossil used to date geologic formations in China. Along with the genus Peipiaosteus, Lycoptera has been considered a defining member of the Jehol Biota, a prehistoric ecosystem famous for its feathered dinosaurs, which flourished for 20 million years during the Early Cretaceous, where it occurs abundantly in often monospecific beds, where they are thought to have died in seasonal mass death events. Lycoptera is a crown group teleost belonging to an early diverging lineage of the Osteoglossomorpha, which contains living mooneyes, arapaima, arowana, elephantfish and knifefish/featherbacks.
Axelrodichthys is an extinct genus of mawsoniid coelacanth from the Cretaceous of Africa, North and South America, and Europe. Several species are known, the remains of which were discovered in the Lower Cretaceous (Aptian-Albian) of Brazil, North Africa, and possibly Mexico, as well as in the Upper Cretaceous of Morocco (Cenomanian), Madagascar and France. The Axelrodichthys of the Lower Cretaceous frequented both brackish and coastal marine waters while the most recent species lived exclusively in fresh waters. The French specimens are the last known fresh water coelacanths. Most of the species of this genus reached 1 metre to 2 metres in length. Axelrodichthys was named in 1986 by John G. Maisey in honor of the American ichthyologist Herbert R. Axelrod.
Undina is a genus of prehistoric coelacanth, lobe-finned fish, which lived from the Triassic period to the Cretaceous period.
Ticinepomis is an extinct genus of coelacanth lobe-finned fish which lived during the Middle Triassic period in what is now Switzerland. It contains two species, T. peyeri and T. ducanensis.
Mawsonia is an extinct genus of prehistoric coelacanth fish. It is amongst the largest of all coelacanths, with one quadrate specimen possibly belonging to an individual measuring 5.3 metres in length. It lived in freshwater and brackish environments from the late Jurassic to the mid-Cretaceous of South America, eastern North America, and Africa. Mawsonia was first described by British paleontologist Arthur Smith Woodward in 1907.
Mawsoniidae is an extinct family of prehistoric coelacanth fishes which lived during the Triassic to Cretaceous periods. Members of the family are distinguished from their sister group, the Latimeriidae by the presence of ossified ribs, a coarse rugose texture on the dermatocranium and cheek bones, the absence of the suboperculum and the spiracular, and reduction or loss of the descending process of the supratemporal. Mawsoniids are known from North America, Europe, South America, Africa, Madagascar and Asia. Unlike Latimeriidae, which are exclusively marine, Mawsoniidae were also native to freshwater and brackish environments. Mawsoniids represent among the youngest known coelacanths, with the youngest known remains of the freshwater genus Axelrodichthys from France and an indeterminate marine species from Morocco being from the final stage of the Cretaceous, the Maastrichtian, roughly equivalent in age to the youngest known fossils of latimeriids. Species of Mawsonia and Trachymetopon are known to have exceeded 5 metres in length, making them among the largest known bony fish to have ever existed.
Lualabaea is an extinct genus of prehistoric coelacanth, belonging to the family Mawsoniidae, containing the single species L. lerichei. It has been found in Late Jurassic or Berriasian aged deposits in the Democratic Republic of the Congo.
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
Trachymetopon is an extinct genus of prehistoric coelacanth from the Jurassic of Europe. Fossils have been found in the Early Jurassic Posidonia Shale of Germany the Middle Jurassic Marnes de Dives of France, and probably the Late Jurassic Kimmeridge Clay of England. Only one species has been named, Trachymetopon liassicum, described by Henning in 1951 from an almost complete specimen found in the Lower Toarcian of Ohmden in Baden-Württemberg. Another specimen is known from the same site, and two older specimens come from the Sinemurian of Holzmaden. The holotype of this species is 1.6 metres in length. A giant specimen of an undetermined species of Trachymetopon found at the Middle Jurassic Falaises des Vaches Noires of Normandy. This specimen, composed of a 53 cm long palatoquadrate, belongs to an individual 4 metres (13 ft) in length. A basisphenoid found in a museum in Switzerland that likely originates from the same locaity probably belonged to an individual around 5 m (16 ft) long, making Trachymetopon the largest of all coelacanths alongside Mawsonia. A study published in 2015 revealed that this coelacanth belongs to the Mawsoniidae. Trachymetopon is one of the few known mawsoniids to have been exclusively marine, while most of the other members of the group have lived in fresh and brackish waters.
Psilichthys is an extinct genus of prehistoric bony fish from Eumeralla Formation, the Lower Cretaceous epoch of what is now Victoria, Australia, known from single species P. selwyni. This is the first Mesozoic fossil vertebrate named from Victoria.
Scheenstia is an extinct genus of neopterygian ray-finned fish from the Late Jurassic–Early Cretaceous of Europe. Fossils have been found in both marine and freshwater environments.
Megalocoelacanthus dobiei is an extinct species of giant latimeriid coelacanth lobe-finned fish which lived during the Lower Campanian epoch until possibly the early Maastrichtian in the Late Cretaceous period in Appalachia, the Western Interior Seaway and Mississippi Embayment. Its disarticulated remains have been recovered from the Eutaw Formation, Mooreville Chalk Formation, and Blufftown Formation of Alabama, Mississippi, and Georgia, and also from the Niobrara Formation of Kansas. Although no complete skeleton is known, careful examination of skeletal elements demonstrate it is closely related to the Jurassic-aged coelacanthid Libys. The species is named for herpetologist James L. Dobie. It has been estimated to have been 3.5—4.5 meters in length.
Foreyia is an extinct genus of coelacanth lobe-finned fish which lived during the Middle Triassic period in what is now Canton of Graubünden, Switzerland. It contains a single species F. maxkuhni.
This list of fossil fish research presented in 2021 is a list of new taxa of jawless vertebrates, placoderms, acanthodians, fossil cartilaginous fishes, bony fishes, and other fishes that were described during the year, as well as other significant discoveries and events related to paleoichthyology that occurred in 2021.
