Coelacanth
Channel: 宇宙のすべての知識 プリンシピア
Date: 02/04/2019

Coelacanth, by Wikipedia https://en.wikipedia.org/wiki?curid=45503 / CC BY SA 3.0

#Coelacanthiformes
#Latimeriidae
#Living_fossils
#Live-bearing_fish
#Ovoviviparous_fish
#Fish_of_the_Comoros
#Fish_of_Indonesia
#Fish_of_Kenya
#Fish_of_Mozambique
#Marine_fish_of_South_Africa
Coelacanth

The coelacanths ( ) constitute a now-rare order of fish that includes two extant 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"). They follow the oldest-known living lineage of Sarcopterygii (lobe-finned fish and tetrapods), which means they are more closely related to lungfish and tetrapods than to ray-finned fishes. They are found along the coastlines of the Indian Ocean and Indonesia. 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 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 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 ("koilos ""hollow" + ἄκανθ-α "akantha" "spine"). It is a common name for the oldest living line of Sarcopterygii, referring to the hollow caudal fin rays of the first fossil specimen described and named by Lou...