The Coelacanth

Coelacanths are large fish that were once known only from fossils. The oldest coelacanth fossils are about 400 million years old, and the most recent ones are about 66 million years old. Because no younger fossils had ever been found, scientists assumed that coelacanths had died out at around the same time as the dinosaurs.

Then, in December 1938, a museum curator in South Africa, Marjorie Courtenay-Latimer, noticed a strange blue fish among a fisherman's catch. She could not identify it, so she sent a sketch of it to a fish expert, J. L. B. Smith, who recognized it as a coelacanth. The discovery caused a sensation around the world. Newspapers called the fish a living fossil, a species that had survived almost unchanged from ancient times.

Coelacanths interest scientists mainly because of their unusual fins. Unlike most fish, they have thick, fleshy fins supported by bones. When they swim, they move these fins in an alternating pattern, much as a four-legged animal moves its legs. Coelacanths are not the ancestors of land animals, but they are distant relatives, so studying them helps scientists understand how the first animals with legs may have evolved.