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Article: Fishes, Cartilaginous
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- Water:Science and Issues
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Fishes, Cartilaginous
Sharks, rays, and chimaeras or ratfishes make up the cartilaginous fishes (Chondrichthyes), one of the two major groups of fishes. The other major group is the ray-finned fishes (Actinopterygii). Unlike the more familiar rayfinned fishes, the cartilaginous fishes have skeletons composed entirely of cartilage. Moreover, cartilaginous fishes possess teeth that are replaced on a regular basis: a single shark may produce over ten thousand teeth in its lifetime. Cartilaginous fishes have four to seven pairs of gill slits that open separately to the outside (except chimaeras have a flap-like covering over the gill slits), lack a swim bladder, and practice internal ...