Fish Skulls & Skeletons

The skeleton is an internal support structure composed of many individual, rigid organs called bones. Bones serve to provide movement of the body (in tandem with muscles and cartilage), as well as to protect internal organs and produce the hematocytes (blood cells) that deliver oxygen and fight infectious diseases. The earliest skeletons developed with the evolution of the first primitive fishes, having first evolved a spine from what was once a flexible notochord. From there, vertebrates (animals with a backbone) would evolve a number of different body styles, though always maintaining the same basic skeletal structure: 1 head, 1 body, 2 arms, 2 legs, and 1 tail. In time, some creatures would adapt in ways to reduce these body parts if the parts in question were no longer subject to necessary selection pressures that came with a changing environment. Examples would include the vestigial femurs of whales that remain in their bodies, or the curved coccyx bone of humans from which there was once a tail (though the coccyx has evolved to provide other functions as well). In rare occasions the bones of deceased animals can become fossils if the environmental conditions are right.