Turtles are vertebrate animals more commonly known as reptiles and are part of a family that has existed for 200 million years. There are two sea turtle families: Dermochelyidae and Cheloniidae. The first has one single species, the leatherback turtle, while the second has two subfamilies, Chelonini and Carettini, that each has two and three subspecies, respectively. Green turtles and hawksbill turtles belong to the Chelonini family, while loggerhead turtles, Olive Ridley turtles and Kemp's Ridley turtles belong to the Carettini family.
Sea turtles are covered in a thick, strong scaly skin. They are protected on the top and their sides by a shell. Under the shell is a large body cavity that contains the turtle's organs and, in the case of a female, a large area to store the turtle's eggs. Interestingly, female turtles can store male turtle's sperm for years, meaning the female turtle can fertilize new eggs without the need to mate. Sea turtles have lungs, but additionally have developed other methods to oxygenate their bodies. Some take in sea water and oxygen is extracted from the water using the pharynx. Others take in water via their anal passage and fill sacs with the water, then release it and collect oxygen from the induced current.
Land turtles also live in water part of the time, with the exception of the turtle family known as the tortoise. There are three species of land turtle in the U.S., namely the box turtle, the ornate box turtle and the wood turtle. The box species lives in open wooded area and prairies while the wood turtle, as the name suggests, lives in damp woods. Their diet is 50 percent plant food and 50 percent insects, although they are known to eat the remains of dead animals.
The anatomy of a land turtle is very similar to that of a sea turtle. The land turtle's vital organs are encased in an armored shell. It has skin that is thick and scaly. However, unlike sea turtles, they breathe only air, and instead of having flippers front and back, they have stumpy legs. Additionally, some land turtles, such as the box turtle, have a hinged shell. This enables the turtle to completely disappear inside its shell.