Presumed gone since the dinosaurs, then netted off South Africa
Coelacanths are lobe-finned actinistians closer to lungfish and tetrapods than to tuna. Fossils suggested Cretaceous extinction until Marjorie Courtenay-Latimer spotted Latimeria chalumnae in a 22 December 1938 trawler haul off the Chalumna River. A Comoran fish followed in 1952; by 1975 some eighty-four specimens were logged.
Louis Agassiz coined the name in 1839 for a Permian fossil whose tail fin rays were hollow, from Greek words for hollow and spine. Over 100 fossil species are now known, the oldest roughly 420 to 410 million years old from the early Devonian of Australia and China. The group was never especially diverse, peaking in the Early Triassic, yet its remains occur on every continent except Antarctica. Some Jurassic and Cretaceous mawsoniids probably topped 5 metres, among the largest bony fishes ever.
When Courtenay-Latimer found the 1938 fish, she mailed sketches to the Rhodes University ichthyologist J. L. B. Smith, who cabled back urging her to keep the skeleton and gills. Surfacing more than 60 million years after its supposed disappearance made it the textbook Lazarus taxon, and the genus Latimeria honours her. Later catches came from Kenya, Tanzania, Mozambique, Madagascar and KwaZulu-Natal. In September 1997 Mark Erdmann and Arnaz Mehta photographed a different coelacanth in a Manado fish market before it was sold; a fisherman handed him a second specimen in July 1998, and the Indonesian species was described in 1999.
Coelacanths have eight fins, including lobed, elongated pectorals, and a three-lobed tail with a small extra tuft at its tip. A rostral organ in the snout senses electric fields, and a joint across the skull may boost bite force. Instead of a backbone, adults keep an oil-filled, pressurised notochord. Fossil forms carried a large calcified lung that probably allowed air breathing, while in Latimeria it has shrunk to a vestige.
Researchers now caution that the living fossil label overstates things: ancient coelacanths varied widely in shape and way of life, and many looked quite unlike Latimeria.
Source: Coelacanth
