The turtle or tortoise body is encased in a shell made up of a series of bony plates covered with a horny shield. The vertebrae and ribs are fused to the inside of this shell, which gives it additional support and strength. It is impossible for turtles or tortoises to crawl out of their shells. Turtles have a relatively flattened shell and are aquatic, while tortoises have a dome-shaped shell and are terrestrial.
