![]() It includes parts of the spine and ribs, meaning the turtle cannot crawl out of its shell. The inner layer of a turtle's shell is made up of about 60 bones. ![]() The carapace and plastron are joined on the turtle's sides by bony structures called bridges. The lower shell that covers the belly is called the plastron. The upper shell of the turtle is called the carapace. Turtles use their tongues to swallow food, but unlike most reptiles, they cannot stick out their tongues to catch food. Herbivorous (plant-eating) turtles have serrated-edged ridges that help them cut through tough plants. Carnivorous (meat-eating) turtles tend to have knife-sharp ridges that help them cut through meat. These ridges are different from teeth, which turtles do not have. Turtles have hard edges called horny ridges that cover their upper and lower jaws. They use their jaws to cut and chew food. The important adaptation of hiding their heads evolved twice from turtles in the past which were not able to do this. The Pleurodira ( side-necked turtles), now found only in fresh water environments in the Southern hemisphere, fold their necks to the side, as it names states. The Cryptodira ( hidden neck turtles) pull their heads straight into their shells by folding their necks back under their spines. Turtles are parted into two groups from the way they hide their heads into their shells. This has inspired genetic researchers to begin studying turtle genetics for longevity (living a long time) genes. They found that the liver, lungs, and kidneys of a century-old turtle are almost the same as those of a younger turtle. Researchers discovered that a turtle's organs do not break down or become less efficient over time, unlike most other animals. When the turtles hatch, they squirm their way to the surface and head toward the water. They are then covered and left to incubate by themselves. Large numbers of eggs are deposited in holes dug into mud or sand. Temperature determines whether an egg develops into a male or a female: a higher temperature causes a female a lower temperature causes a male. In some species, there is temperature-dependent sex determination. Turtles can take many years to reach breeding age, and in many cases breed every few years rather than annually. Sea turtles lay their eggs on dry, sandy beaches. Other turtle species have eggs that are shaped more like chicken eggs. The eggs of the largest species are shaped like spheres (evenly round like a ball). ![]() Like other reptiles, turtles lay eggs which are slightly soft and leathery. Turtles usually lay their eggs on beaches Unfortunately, Chelonia is also the name of a particular genus of turtles, so this conflicts with its use for the entire order Testudines.Įcology and life history To avoid confusion, the word "chelonian" is popular among some who work with these animals, as a catch-all name.
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