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The bony fishes (Class Osteichthyes) contain more species than all other vertebrate groups combined. They show a fantastic adaptive radiation into almost every conceivable aquatic niche and come in a variety of sizes, shapes, colors, etc. Among the most primitive forms are those found in the Subclass Crossopterygii, which contains some of the lobe-finned fishes, a name that refers the fact that their fins are supported by fleshy lobes (rather than by the bony rays seen in modern fishes). Until 1938, this group (which is well represented in the fossil record) was thought to have been extinct for over 60 million years. At that time, a living specimen was dredged up by fisherman from the depths of the ocean off the coast of South Africa. Scientists had to wait until 1952 before another specimen was found, and even today, very little is known about the fish known as the coelacanth. More recently, a few specimens (of what is apparently a different species) have been discovered in the seas off the island nation of Indonesia. With sturdy skeletons of the basic tetrapod (four legged) type and fleshy lobe-fins that can be used like legs to crawl across the bottom, a lobe-finned fish (perhaps from the group containing the coelacanth or from another group) almost certainly gave rise to the limbed vertebrates that roam the land today! |
