The Osteichthyes, or bony fish, make up about half of vertebrate species diversity. Their success is due to a combination of adaptations that include:

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The mobile jaws in bony fish allow for specialized feeding, while their kidneys allow for fine regulation of water balance. While some bony fish do have modified swim bladders that function as lungs, and some undergo metamorphosis, not all species have these adaptations. The presence of paired, fleshy pectoral and pelvic fins are common in most fish, but not unique to bony fish.

The Osteichthyes, or Bony Fish, Make Up About Half of Vertebrate