Turtles have been on the earth for more than 200 million years. They got here before birds, crocodiles, snakes, and lizards. The earliest turtles had teeth and could not pull their heads into their shells. But turtles these days are very similar. Turtles range in size from the 4-inch Bog Turtle to the 1,500-pound Leathery Turtle. The top part of the turtle’s shell is called the carapace and the bottom part is called the plastron. The shell of a turtle is made up of 60 different bones all connected together. Most land tortoises have high carapaces that give the turtle protection from predators. Aquatic turtles usually have flatter shaped shells. Turtles are one of the oldest groups of reptiles.