The coelacanths (/ˈsiːlə.kænθ/ SEE-lə-kanth) constitute a now rare order of fish that includes two extant species in the genus Latimeria: the West Indian Ocean coelacanth primarily found near the Comoro Islands off the east coast of Africa (Latimeria chalumnae) and the Indonesian coelacanth (Latimeria menadoensis). They follow the oldest known living lineage of Sarcopterygii (lobe-finned fish and tetrapods), which means they are more closely related to lungfish, reptiles and mammals than to the common ray-finned fishes. They are found along the coastlines of the Indian Ocean and Indonesia. Since there are only two species of coelacanth and both are threatened, it is the most endangered order of animals in the world. The West Indian Ocean coelacanth is a critically endangered species. Coelacanths belong to the subclass Actinistia, a group of lobed-finned fish related to lungfish and certain extinct Devonian fish such as osteolepiforms, porolepiforms, rhizodonts, and Panderichthys. Coelacanths were thought to have become extinct in the Late Cretaceous, around 66 million years ago, but were rediscovered in 1938 off the coast of South Africa. The coelacanth was long considered a “living fossil” because it was believed to be the sole remaining member of a taxon otherwise known only from fossils, with no close relations alive, and to have evolved into roughly its current form approximately 400 million years ago. However, several recent studies have shown that coelacanth body shapes are much more diverse than previously thought.

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