Coelacanth

Coelacanths (/ˈsiːləkænθ/ ^ⓘ SEE-lə-kanth) are an ancient group of lobe-finned fish (Sarcopterygii) in the class Actinistia. As sarcopterygians, they are more closely related to lungfish and tetrapods (the terrestrial vertebrates including living amphibians, reptiles, birds and mammals) than to ray-finned fish.

The name coelacanth originates from the Permian genus Coelacanthus, which was the first scientifically named genus of coelacanths (in 1839), becoming the type genus of Coelacanthiformes as other species were discovered and named. Well-represented in freshwater and marine deposits from as early as the Devonian period (more than 410 million years ago), they were thought to have become extinct in the Late Cretaceous, around 66 million years ago.

The first living species, Latimeria chalumnae, the West Indian Ocean coelacanth, was described from specimens fished off the coast of South Africa from 1938 onward; they are now also known to inhabit the seas around the Comoro Islands off the east coast of Africa. The second species, Latimeria menadoensis, the Indonesian coelacanth, was discovered in the late 1990s, which inhabits the seas of Eastern Indonesia, from Manado to Papua.

The coelacanth (more accurately, the extant genus Latimeria) is often considered an example of a "living fossil" in popular science because it was considered the sole remaining member of a taxon otherwise known only from fossils (a biological relict), evolving a bodyplan similar to its current form approximately 400 million years ago. However, studies of fossil coelacanths have shown that coelacanth body shapes (and their niches) were much more diverse than what was previously thought, and often differed significantly from Latimeria.

The word Coelacanth is an adaptation of the Modern Latin Cœlacanthus ('hollow spine'), from the Ancient Greek κοῖλ-ος (koilos, 'hollow') and ἄκανθ-α (akantha, 'spine'), referring to the hollow caudal fin rays of the first fossil specimen described and named by Louis Agassiz in 1839, belonging to the genus Coelacanthus. The genus name Latimeria commemorates Marjorie Courtenay-Latimer, who discovered the first specimen.

The earliest fossils of coelacanths were discovered in the 19th century. Coelacanths were believed to have become extinct at the end of the Cretaceous period. More closely related to tetrapods than to the ray-finned fish, coelacanths were considered a transitional form between fish and tetrapods.

On 22 December 1938, the first Latimeria specimen was found off the east coast of South Africa, off the Chalumna River (now Tyolomnqa). Museum curator Marjorie Courtenay-Latimer discovered the fish among the catch of a local fisherman. Courtenay-Latimer contacted a Rhodes University ichthyologist, J. L. B. Smith, sending him drawings of the fish, and he confirmed the fish's importance with a famous cable: "Most Important Preserve Skeleton and Gills = Fish Described." Its discovery over 60 million years after its supposed extinction makes the coelacanth the best-known example of a Lazarus taxon, a taxon or an evolutionary line that seems to have disappeared from the fossil record only to reappear much later. Since 1938, West Indian Ocean coelacanth have been found in the Comoros, Kenya, Tanzania, Mozambique, Madagascar, in iSimangaliso Wetland Park, and off the South Coast of Kwazulu-Natal in South Africa.

The Comoro Islands specimen was discovered in December 1952. Between 1938 and 1975, 84 specimens were caught and recorded.