Fish: Chondrichthyes vs. OsteichthyesWhat makes Chondrichthyes different from Osteichthyes is that they have skeletons made of cartilage, they don't have swim bladders, and they have gill slits.This means they must keep swimming so they do not sink. Osteichthyes have swim bladders (which keep them afloat), they have operculums which cover their gill slits, and they also have skeletons made of bone.
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