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.
Sarcopterygii — sometimes considered synonymous with Crossopterygii — is a taxon of the bony fish known as the lobe-finned fish or sarcopterygians, characterised by prominent muscular limb buds (lobes) within the fins, which are supported by articulated appendicular skeletons. This is in contrast to the other clade of bony fish, the Actinopterygii, which have only skin-covered bony spines (lepidotrichia) supporting the fins.
Macropoma is an extinct genus of coelacanth in the class Sarcopterygii. Fossils of Macropoma have been found in both England and Czech Republic, dating to the mid-Cretaceous (Albian-Turonian). Recorded fossils have bodies under two feet in length. A modern coelacanth measures five or more, but in other respects the two genera are remarkably similar, and share the same body plan with a three-lobed tail and stalked fins.
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.
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.
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.
Laugiidae is an extinct family of prehistoric lobe-finned fishes which lived during the Triassic and Jurassic periods. Their fossils has been found in Canada, China, Germany and Greenland.
Indocoelacanthus robustus is a fossil sarcopterygian. The holotype specimen was found in Lower Jurassic-aged riverine sediment of the Kota formation, in the Pranhita-Godavari valley at Boraigudem limestone ridge, about 30 kilometers southeast of Sironcha, India. The holotype is preserved in the museum of the Indian Statistical Institute.
Heptanema is an extinct genus of prehistoric coelacanth from the Middle Triassic (Ladinian) of northern Italy and southern Switzerland.
Mylacanthus is an extinct genus of prehistoric coelacanth lobe-finned fish that lived during the Smithian age of the Early Triassic epoch in what is now Svalbard.
Sassenia is an extinct genus of prehistoric coelacanth lobe-finned fish that lived during the Early Triassic epoch in what is now East Greenland and Svalbard.
Swenzia is an extinct genus of coelacanthid fish from the late Jurassic of France. It contains a single species, S. latimerae, which was originally described as Wenzia latimerae. Because the generic name Wenzia was already preoccupied by a snail, the generic name was amended to Swenzia. It is the fossil genus most closely related to the living coelacanth, Latimeria.
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.
Shoshonia is a Devonian-era extinct genus of prehistoric sarcopterygians, or lobe-finned fish. It contains one species, Shoshonia arctopteryx. The fish was named in reference to the Shoshoni people and the Shoshone National Forest in Wyoming, in the United States.
Qingmenodus is a genus of prehistoric lobe-finned fish. Fossils of Qingmenodus were found in China and date back to the Early Devonian period. Qingmenodus reveals the first well-ossified otoccipital braincase in onychodonts. Palaeontologists believe that Qingmenodus was one of the oldest onychodont fish.
The evolution of fish began about 530 million years ago during the Cambrian explosion. It was during this time that the early chordates developed the skull and the vertebral column, leading to the first craniates and vertebrates. The first fish lineages belong to the Agnatha, or jawless fish. Early examples include Haikouichthys. During the late Cambrian, eel-like jawless fish called the conodonts, and small mostly armoured fish known as ostracoderms, first appeared. Most jawless fish are now extinct; but the extant lampreys may approximate ancient pre-jawed fish. Lampreys belong to the Cyclostomata, which includes the extant hagfish, and this group may have split early on from other agnathans.
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.
Parnaibaia is a genus of coelacanth fish which lived during the Late Jurassic period. Fossils of Parnaibaia have been found in the Pastos Bons Formation in Maranhão, Brazil. Parnaibaia was described for the first time by palaeontologist Yoshitaka Yabumoto in 2008.
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.
