On this date, a coelacanth (Latimeria chalumnae) was caught at the mouth of the Chalumna River on the east coast of South Africa. The fish was caught in a shark gill net by Captain Goosen and his crew, who had no idea of the significance of their find. They thought the fish was bizarre enough to alert the local museum in the small South African town of East London.
The director of the East London Museum at the time was Miss Marjorie Courtney-Latimer. She alerted the prominent south African ichthyologist Dr J.L.B. Smith to this amazing discovery. This modern coelacanth was eventually named in honor of Miss Courtney-Latimer.
This coelacanth specimen led to the discovery of the first documented population, off the Comoros Islands, between Africa and Madagascar. For sixty years this was presumed to be the only coelacanth population in existence. However, on July 30, 1998, a coelacanth was caught in a deep-water shark net by local fishers off the volcanic island of Manado Tua in northern Sulawesi, Indonesia, about 10,000 km east of the Western Indian Ocean coelacanth population. In 1999 the Sulawesi coelacanth was described as a new species, Latimeria menadoensis, by Pouyaud, Wirjoatmodjo, Rachmatika, Tjakrawidjaja, Hadiaty and Hadie.
In 1836, the eminent naturalist Louis Agassiz described the first fossil coelocanth. Since then, fossils of some 125 species have been discovered, dating back over 360 million years, with a peak in abundance about 240 million years ago. Before 1938, coelacanths were thought to have become extinct approximately 66 million years ago, when they disappeared from the fossil record, so the discovery of a living coelacanth was very significant.
But why are there no coelacanth fossils since the days of the dinosaurs? The explanation seems to be that the coelacanths from the fossil record lived in environments favoring fossilization, whereas modern coelacanths, both in the Comoros and Sulawesi, are found in environments that do not favor fossil formation. They inhabit caves and overhangs in nearly vertical marine reefs, at about 200 meters depth, off newly formed volcanic islands.
One of the most distinctive features of the coelacanth is that, along with all six living species of lungfishes but unlike all other fishes, it has paired “lobed fins”. The fins of such “lobe-finned fishes” project from the body on stalks rather than attaching directly to the body. The stalks that support the fins contain the same basic bones as the arms and legs of terrestrial four-limbed animals (tetrapods). Coelacanths even move their paired fins much like land animals move their limbs: The right pectoral fin moves in conjunction with the left pelvic fin, for example. And their movement is extremely dexterous; they scull the water like oars and can rotate through 180 degrees.
In fact, at the time of its discovery in 1938, the coelacanths were thought to be the ancestors of the tetrapods. Although it is now thought that the lungfishes are the closest living relative of tetrapods, the coelacanths may still provide answers to some very interesting evolutionary questions.
Other interesting features of the coelacanths include an intracranial joint and a rostral organ, not known in any other living fish.
- Samantha Weinberg. A Fish Caught in Time: The Search for the Coelacanth (Harper Perennial, 2001).