Pig-Nose Turtle: Carettochelyidae

This family has only one member: the pig-nose turtle. This is quite a large freshwater turtle, with an upper shell that can reach 22 inches (56 centimeters) in length and 14 inches (35.6 centimeters) in width. It may weigh up to 50 pounds (22.7 kilograms). It often swims with just its long snout sticking out of the water. That long snout is one of its most notable features. A fleshy, tube-shaped structure, it is similar in appearance to the snout of a pig. The shell of the pig-nose turtle is also different from that of most other turtles. The shells of most turtles are covered in bony plates, called "scutes" (SCOOTS). The pig-nose turtle, on the other hand, has a hard shell with a leathery covering.

This turtle also has long front legs that can stretch to a length almost half as long as the carapace (KARE-a-pays), or upper shell. The legs are flat and wide, like paddles or flippers. In fact, the limbs, or legs, more nearly look like the front legs of marine turtles, or turtles that live in the sea, than those of other freshwater turtles. Each front limb is tipped with two claws. In color, the turtle is mostly olive or gray on the tops of its limbs and high-domed upper shell and is whitish or yellowish on its bottom shell, or plastron (PLAS-trun), and on its chin, lower neck, and the undersides of its limbs. Males and females look very much alike, except for the male's larger tail. Besides their smaller size, juveniles (JOO-vuh-nuhls), or young turtles, differ from adults in the smoothness of the carapace. The juvenile carapace has a lumpy ridge, called a "keel," down the middle and is jagged along the edge, whereas the adult carapace does not have a keel anywhere except toward the back, and it is rounded at the edge.

At one time scientists believed that these turtles should be included with the side-necked turtles, a group known as the Pleurodira, rather than the hidden-necked turtles, or the Cryptodira. The better-known hidden-necked turtles pull their heads and necks straight back into their shells, whereas side-necked turtles fold their necks sideways. Scientists based their decision mostly on the location of the first turtle discovered back in the late 1800s. The original specimen (SPEH-suh-muhn), or example, was not whole; it was missing the part of its backbone that would have shown scientists whether it was a side-necked or a hidden-necked turtle. Because it was found in New Guinea and all of the other turtles known from New Guinea or from Australia at that time were of the side-necked variety, the scientific community assumed that the pig-nose turtle must be a side-necked turtle too. As more of these turtles turned up, however, scientists were able to take a closer look at the backbone, and they discovered that this species should be considered a hidden-necked turtle.