Categories
Animals

Ostracoderms – soft shelled fish

Many hot arguments have been held over the proper popular name for a given fish. It usually turns out that both sides were right; a fish having a certain popular name in one part of the country may be called by a different one somewhere else. What we call the zebra fish, for example, is also known as the lion fish, turkey fish, butterfly cod, devil fish, dragon fish, stingfish, firefish, and fireworks fish.

The better recognized a fish is, the more popular names it seems to have; for instance, no less than forty-four different names have been recorded for the well-known largemouth black bass. At one time or another this fish has been called green bass, white bass, gray bass, yellow bass, spotted bass, striped bass, straw bass, moss bass, mud bass, rock bass, river bass, lake bass, marsh bass, bayou bass, and cow bass.

It has also been called a green or white trout, a white salmon, a green or yellow pond perch, and a southern chub. Many of these names have been traditionally attached to entirely different species. Many are confusing in that a member of the fresh-water black bass and sunfish family cannot very well also be a member of the perch or the salmon and trout family.

An effort to straighten out this confusion has recently been made by the American Fisheries Society, the Outdoor Writers Association of America, and the Board of Conservation of Florida, working through the University of Miami. Each has published a valuable check list of fishes that includes a careful selection of popular names. Since it is clearly impossible for us to list even a part of the multitudinous synonyms belonging to most fish of the succeeding series of “biographies,” we have followed these authorities, especially the first, in our choice of popular names.

Fishes form the oldest group of vertebrates, that is to say, they were the first backboned animals to develop on the earth. The earliest fossil record of them dates back to the Ordovician period, some four hundred million years ago.

These fish, which we call “Ostracoderms” (meaning “shell-skinned”), were heavily armored and had no jaws. The head and front part of the body were encased in a shieldlike, bony, external cover. Most species were small, and all of them were certainly not “built for speed.” They apparently poked along the bottom, sucking in dead organic matter for food, and depending on their armor for protection. None of these ancient fishes is alive today; they have been extinct for the last 28o million years. Their nearest living relatives are the jawless fishes – the lampreys and hagfishes – of the class Cyclostomi (“circular mouthed”).

During succeeding millions of years other groups of armored fishes appeared and disappeared. Sharks first show up in geological deposits that are somewhat more than three hundred million years old. Their descendants constitute the class Chondrichthyes (“cartilage-fishes”), which have gristle instead of true bone in their skeletons.