The coelacanth (Latimeria chalumnae) is an enigmatic and important species of "fish."
It is the only living member (along with a recently discovered second species of Latimeria) of the lobe-finned fishes, a group believed by some to be the sister-group of the terrestrial vertebrates. Together, these fishes along with lungfish (see Chirodipterus sp.), amphibians, and amniotes are known as the Sarcopterygii. The first specimen of the coelacanth was not discovered until 1938 off the coast of South Africa. The largest populations are known from the Comoros Islands, which lie between the mainland of Africa and Madagascar.
In these images from the scan you can see the characteristic notochord and intracranial joint.
The fossil record of the coelacanths, or Actinistia, comprises some 125 species grouped into approximately 50 genera and four to ten families. Fossils are known from the Middle Devonian (380 million years ago) through the end of the Cretaceous (70 million years ago), when the coelacanths (and non-avian dinosaurs) were thought to have become extinct.
Latimeria can reach a length of almost six feet (nearly 2 meters) and weigh up to 95 kg, but they are usually somewhat smaller, particularly the males, which average under 165 centimeters in length. They are opportunistic feeders, eating small fishes and invertebrates found in their deep reef and volcanic slope habitats. Coloration is dark blue with distinctive white flecks that can even be used by researchers to designate individuals. (Indonesian coelacanths may be more brown than blue). Scientists believe individual coelacanths may live as long as 60 years.
One of the more fascinating aspects of their biology is that they are ovoviparous, giving birth to as many as 26 live pups which develop from eggs in the oviduct. The young feed off a large yolk sac until birth. Gestation is lengthy, probably 13 months. Combined with late maturation, reproduction rates are very slow and the species is undoubtably at risk of extirpation. Although the Comoran government has outlawed the capture of coelacanths, there is an incidental bycatch and black market trade in specimens due to the perceived value of the fluid in their notochord as a life lengthening supplement for humans.
The discovery of the coelacanth is an important addition to our understanding of vertebrate evolution. The early phylogenetic history of tetrapods has been (in fact, still is) quite controversial. The “players” in this drama are all of the vertebrates comprising the sister group to bony fishes: lungfish, amphibians, the coelacanth, early amniotes and a variety of extinct taxa known only from fossils. The two hypotheses below represent the most common of several possible historical relationships of these taxa.
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The coelacanth on The Australian Museum fish site
Latimeria chalumnae on the Animal Diversity Web (The University of Michigan Museum of Zoology)