LYCOS RETRIEVER 
Turtles: Shells
built 290 days ago
Turtles are divided into three suborders, one of which, the Paracryptodira, is extinct. The two extant suborders are the Cryptodira and the Pleurodira. The Cryptodira is the larger of the two groups and includes all the marine turtles, the terrestrial tortoises, and many of the freshwater turtles. The Pleurodira are sometimes known as the side-necked turtles, a reference to the way they withdraw their heads into their shells. This smaller group consists primarily of various freshwater turtles.
Source:
Australian flatbacks are medium size turtles that inhabits coastal coral reef and grassy shallows and is only found in the northern coastal area of Australia and the Gulf of Papua, New Guinea. The shell is very smooth and waxy, and can be easily damaged.
Source:
Most aquatic turtles have flat, streamlined shells which aid in swimming and diving. American snapping turtles and musk turtles have small, cross-shaped plastrons that give them more efficient leg movement for walking along the bottom of ponds and streams.
Source:
MORE ABOUT
Shells