The coelacanth is a crossopterygian (lobe-finned) fish, Latimeria chalumnae, who’s fossil record dates back more than 350 million years to the Devonian Period, (preceding the dinosaurs by more than 100 million years). Paleontologists once assumed that it had become extinct at the end of Cretaceous time (about 65 million years ago).

There were two main lines in the Crossopterygii, named Coelacanths and Rhipidistia. Fossil remains indicate how closely they are related. Because somewhat earlier fossils of the Rhipidistia than those of Coelacanths are known, most scientists today hold the view that the Rhipidistia came first and the Coelacanths developed from them.

Rhipidistia Eusthenopteron

The coelacanth has a deep and stocky body, and its paired dorsal fins are rounded and lobelike as in fossilized members of the order Crossopterygii. The dorsal and anal fins are fan-shaped. The first spine of the dorsal fin is hollow; the fish’s name means “hollow spine” in Greek. The skeletal structure of the pectoral and pelvic fins indicates a close evolutionary relationship between the coelacanth and four-limbed land vertebrates . Underwater pictures show the fish moving like four-legged animals. Coelacanths also have symmetrical three-lobed tails, distinguished by a small central lobe that projects beyond the larger upper and lower lobes. The head is short and deep, and the bones of the skull are considerably reduced. The coelacanth is carnivorous.