Fish for Life - 3867 Words
Fish cold-blooded, limbless, completely aquatic vertebrates, having gills, commonly fins, and typically elongated torpedo-shaped body mostly covered with scales. Fish are usually grouped into four classes, three living (Agnatha, Chondrichthyes, and Osteichthyes) and one extinct (Placodermi): 1. Agnatha, the primitive jawless fishes, including the cyclostomes (lampreys and hagfishes) and extinct armoured fishes known as ostracoderms, none of which has gill arches (bony frames for the...
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