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 clade including both a group of bony fish commonly referred to as lobe-finned fish, and tetrapods. They are characterised by prominent muscular limb buds (lobes) within their 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 supporting the fins.
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.
Coelacanthus is a genus of extinct marine coelacanths known from the late Permian period. It was the first genus of coelacanths described, about a century before the discovery of the extant coelacanth Latimeria. The order Coelacanthiformes is named after it.
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.
Coccoderma is an extinct genus of prehistoric marine coelacanth which lived during the Late Jurassic period. Fossils have been found in Germany and France. It was small in size, about 27.5 cm. They had very long and sharp teeth.
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.
Whiteia is an extinct genus of prehistoric coelacanth fish which lived during the Triassic period. It is named after Errol White.
Laugiidae is an extinct family of prehistoric marine coelacanths which lived during the Triassic and Jurassic periods. Their fossils have been found in Canada, Germany and Greenland.
Coelacanthopsis is an extinct genus of marine coelacanth which lived during the early Carboniferous (Mississippian). It is known from one species, C. curta from the Viséan of Ardross, Scotland.
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.
Moenkopia is an extinct genus of prehistoric sarcopterygians from the Coelacanthidae found in the Middle Triassic Moenkopi Formation of Arizona. The type, and only species, M. wellesi, was named in 1961 in honour of Samuel Paul Welles. It is only known from the holotype, UMCP 36193, a partial skull consisting only of the basisphenoid that was collected in 1939 or 1940 by Samuel Welles and briefly noted on by him in 1947, and other assorted specimens found before 2005 in the Radar Mesa by S. J. Nesbitt, W. G. Parker and R. B. Irmis.
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.
Youngichthys is an extinct genus of prehistoric sarcopterygians or lobe-finned fish from the upper Permian (Changhsingian) comprising a single species, Youngichthys xinghuansis. The single specimen of the fish was discovered in Zhejiang Province, China in 1981.
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.
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.
Serenichthys kowiensis is a fossil species of coelacanth described in 2015 from near Grahamstown in South Africa.
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.
