Coelacanths: The Extinct Fish Found Alive in 1938

A coelacanth is a deep-sea, lobe-finned fish that scientists knew only from fossils until a living one was pulled from a fishing net in 1938. The group is ancient: its fossils run from about 409 million to 66 million years ago, and then stop.

The feature that sets it apart is the fins. A coelacanth has eight fins, and several of them grow from fleshy, lobed stalks rather than spreading straight from the body on thin rays the way a trout's or a bass's do. That makes it a lobe-finned fish, a lineage that is now tiny: Wikipedia's fish article counts only eight living lobe-finned species, the two coelacanths plus the lungfishes, against more than 32,000 ray-finned bony fish.

The two living species are:

• West Indian Ocean coelacanth (Latimeria chalumnae), known from South Africa and the Comoro Islands; the one caught in 1938
• Indonesian coelacanth (Latimeria menadoensis), identified from a fish market on Sulawesi in 1997 and confirmed as a separate species by DNA

On 22 December 1938 a fishing boat landed an unusual fish near East London, South Africa. Marjorie Courtenay-Latimer, curator of the East London Museum, recognised that it was unusual and contacted the fish expert JLB Smith of Rhodes University. The specimen was about 1.5 m long. Smith named it Latimeria chalumnae, the genus honouring her, and the Natural History Museum in London notes that newspapers in April 1939 called it the sensation that had outdone the Loch Ness monster.

Finding a second one took 14 years. In 1952 a fisherman, Ahmadi Abdulla, caught one in the Comoro Islands, roughly 2,000 km from the first site.

The third chapter came in 1997, when Arnaz Mehta Erdmann and her husband Mark, an ichthyologist, saw a coelacanth at an outdoor market on Sulawesi, Indonesia. Local fishermen called it raja laut, king of the sea. A second Indonesian specimen followed in 1998, and DNA work showed it was a different species, named Latimeria menadoensis.

The coelacanth never actually went extinct. It only looked that way because the fossil record stops about 66 million years ago. Biologists call a group like this a Lazarus taxon: something that vanishes from the fossils and later turns up alive.

The Natural History Museum gives two reasons it went unnoticed. The living species have small, restricted ranges, and they live in deep water along steep volcanic slopes, a setting where fossils rarely form. So the gap in the record reflects where fossils happen to be preserved, not a real disappearance.

Beyond the lobed fins, the living coelacanth keeps several features that are rare or unique among living fish (Wikipedia):

• Rostral organ: a sensory organ in the snout used for electroreception, detecting the weak electric fields of prey
• Intracranial joint: a hinge inside the skull that lets the front of the head lift when the mouth opens
• Oil-filled notochord: instead of a fully bony backbone, an adult keeps a flexible, oil-filled tube, a feature most vertebrates have only as embryos
• Vestigial lung: a reduced lung, a leftover of the lineage's past
• Live birth: eggs hatch inside the mother, who gives birth to 5 to 25 pups; the NHM says pups are about 30 cm long at birth

It is a slow life. Wikipedia reports sexual maturity after about 20 years, and the NHM cites research suggesting a lifespan of around 100 years.

One popular idea is wrong: the coelacanth is not the missing link between fish and land animals. Lobe-finned fish are closer to four-legged animals than ray-finned fish are, but the NHM points out that lungfishes are more closely related to land vertebrates than coelacanths are.

When people search for a fish that is pregnant for five years, the answer is the coelacanth. Wikipedia gives a gestation period of up to five years.

Sources do not agree on the figure. The Natural History Museum page describes gestation as over a year, while Wikipedia gives up to five years. Both describe a very slow life: the NHM cites research suggesting a lifespan of about 100 years, and Wikipedia puts sexual maturity at around 20 years. Treat the five-year figure as the upper estimate.

Nobody knows the total, because the fish live deep and are rarely seen. The best-known figure is from a 2011 study cited by the Natural History Museum, which estimated 300 to 400 individuals around Grande Comore.

The West Indian Ocean coelacanth is listed as Critically Endangered and the Indonesian species as Vulnerable, and both are protected from international trade under CITES. Wikipedia names accidental capture in deep-sea trawling as the main current threat.

Fame made things worse for a while. The NHM describes how reward schemes in the Comoros led to targeted fishing, how London Zoo was prepared to spend £1,000 on one in 1952, how Japan's Toba Aquarium put £1.3 million into a 1989 project, and how black-market prices reached about £100,000 a fish by 1992.

Coelacanths are not a food fish, and nobody should try one. Wikipedia reports that the flesh holds large amounts of oil, urea and wax esters, which make it hard to digest and cause stomach and intestinal upset. The NHM says the fish had little value as food before scientists took an interest.

Both species are also protected, so there is no legal trade. If a fisherman in the Comoros or Indonesia brings one up, the right step is to report it to local fisheries or scientific authorities.

The coelacanth is the most famous fish that seemed extinct and came back, but many fish really are gone. Two examples show the range:

• Dunkleosteus: an armoured placoderm that lived about 382 to 358 million years ago in the Late Devonian. Older books gave lengths of 6 to 10 m, but recent studies put typical adults at about 3.4 m, with the largest perhaps 4.1 m (Wikipedia).
• Harelip sucker: a North American freshwater fish from the Ohio basin, the Ozarks and the Lake Erie drainage. It has not been seen alive since 1893 and was considered extinct by 1970. Wikipedia attributes the loss to silt from 19th-century deforestation and farming, which clouded the water this sight-feeding fish depended on.

The contrast is useful. Dunkleosteus left no living relatives; the coelacanth's lineage simply went unrecorded for 66 million years.

Research and drafting for this page were assisted by AI and checked line by line against the sources listed below. Every number names the organisation it comes from; where sources disagree we say so rather than pick one silently. Rules and advisories change, so treat the dates given here as the date we checked. If you find an error, tell us and we will correct it.