Coelacanth

Coelacanths (ˈsiːləkænθ ) (order Coelacanthiformes) are an ancient group of lobe-finned fish (Sarcopterygii) in the class Actinistia. As sarcopterygians, they are more closely related to lungfish and tetrapods (which includes amphibians, reptiles, birds and mammals) than to ray-finned fish. Well-represented in both freshwater and marine fossils since the Devonian, they are now represented by only two extant marine species in the genus Latimeria: the West Indian Ocean coelacanth (Latimeria chalumnae), primarily found near the Comoro Islands off the east coast of Africa, and the Indonesian coelacanth (Latimeria menadoensis). The name "coelacanth" originates from the Permian genus Coelacanthus, which was the first scientifically named coelacanth. The oldest known coelacanth fossils are over 410 million years old. Coelacanths were thought to have become extinct in the Late Cretaceous, around 66 million years ago, but were discovered living off the coast of South Africa in 1938. The coelacanth was long considered a "living fossil" because scientists thought it was the sole remaining member of a taxon otherwise known only from fossils, with no close relations alive, and that it evolved into roughly its current form approximately 400 million years ago. However, several more recent studies have shown that coelacanth body shapes are much more diverse than previously thought. The word Coelacanth is an adaptation of the Modern Latin Cœlacanthus ("hollow spine"), from the Greek κοῖλ-ος (, "hollow") and ἄκανθ-α (, "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, which are related to lungfishes and tetrapods, were believed to have become extinct at the end of the Cretaceous period.