![]() 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. Australian English uses turtle for both the marine and freshwater species, but tortoise for the terrestrial species.The name "terrapin" is not as commonly heard. "Tortoise" is used for most land-dwelling species, and oceanic species are usually referred to as sea turtles. American English tends to use the word turtle as a general term for all species.British English describes these reptiles as turtles if they live in the sea terrapins if they live in fresh water or tortoises if they live on land.How these names are used depends on the type of English. Turtle, tortoise, or terrapin Īlthough the word turtle is widely used to describe all members of the order Testudines, it is also common to see certain members described as terrapins, tortoises or sea turtles. A lot of the turtle species alive today are endangered. Turtles are almost everywhere in the world. Turtles come from ancient turtles, which had spiked shells. Turtles have been on earth for longer than lizards, snakes and crocodiles. ![]() Turtles are one of the oldest reptile groups that are not extinct. The fossil was from about 220 million years ago. The earliest fossil of a turtle was found in China from the early Upper Triassic age. The order Testudines (which includes turtles) includes both living and extinct species. There are about 356 species of turtles living on land in all continents except Antarctica and in both salt water and fresh water. Side-necked turtles have very easy to see necks, but hidden neck turtles have very small necks. There are two types of turtles: side-necked turtles and hidden neck turtles. Turtles are a type of reptile with hard shells on their back.
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