Turtle
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Turtle, reptile with a bony or leathery shell. Any shelled reptile can be called a turtle, but in North America people commonly use the word tortoise to designate members of a family of turtles that live entirely on land, reserving the word turtle for species that live in or near water.
The upper shell of the turtle, under which the head, limbs, and tail can be more or less completely withdrawn, is called the carapace. The lower shell, which encases the belly, is called the plastron. The carapace and plastron are joined together on a turtle’s left and right sides by bony structures called bridges. The inner layer of a turtle’s shell is composed of about 60 bones, including portions of the backbone and the ribs. For this reason, a turtle cannot crawl out of its shell.
Most turtles and tortoises have conspicuous eyes placed well forward on the upper sides of their heads. Turtle species that live most of their lives on land usually focus their eyes downward toward objects in front of them. Some water-living turtles, like snapping turtles and soft-shelled turtles, have eyes nearer the top of the head. These turtles can hide from predators and prey in shallow bodies of water, where they lie nearly entirely submerged except for their eyes and nostrils. Sea turtles have glands near their eyes that produce salty tears, ridding the turtles’ bodies of the excess salt that they take in from drinking seawater. When a sea turtle is in the water, its tears are immediately washed away, but when these turtles arrive on land, they look as though they are crying.
Turtles use their jaws to cut and handle food. Instead of teeth, a turtle’s upper and lower jaws are covered by horny ridges, similar to a bird’s beak. Meat-eating turtles commonly have knife-sharp ridges for slicing through their prey. Plant-eating turtles often have ridges with serrated edges that help them cut through tough plants. Turtles use their tongues in swallowing food, but unlike many other reptiles, such as chameleons, they cannot stick out their tongues to capture food.
Scientific classification: Turtles make up the order Testudines in the class Reptilia. Hidden-necked turtles make up the suborder Cryptodira, and side-necked turtles comprise the suborder Pleurodira.
The upper shell of the turtle, under which the head, limbs, and tail can be more or less completely withdrawn, is called the carapace. The lower shell, which encases the belly, is called the plastron. The carapace and plastron are joined together on a turtle’s left and right sides by bony structures called bridges. The inner layer of a turtle’s shell is composed of about 60 bones, including portions of the backbone and the ribs. For this reason, a turtle cannot crawl out of its shell.
Most turtles and tortoises have conspicuous eyes placed well forward on the upper sides of their heads. Turtle species that live most of their lives on land usually focus their eyes downward toward objects in front of them. Some water-living turtles, like snapping turtles and soft-shelled turtles, have eyes nearer the top of the head. These turtles can hide from predators and prey in shallow bodies of water, where they lie nearly entirely submerged except for their eyes and nostrils. Sea turtles have glands near their eyes that produce salty tears, ridding the turtles’ bodies of the excess salt that they take in from drinking seawater. When a sea turtle is in the water, its tears are immediately washed away, but when these turtles arrive on land, they look as though they are crying.
Turtles use their jaws to cut and handle food. Instead of teeth, a turtle’s upper and lower jaws are covered by horny ridges, similar to a bird’s beak. Meat-eating turtles commonly have knife-sharp ridges for slicing through their prey. Plant-eating turtles often have ridges with serrated edges that help them cut through tough plants. Turtles use their tongues in swallowing food, but unlike many other reptiles, such as chameleons, they cannot stick out their tongues to capture food.
Scientific classification: Turtles make up the order Testudines in the class Reptilia. Hidden-necked turtles make up the suborder Cryptodira, and side-necked turtles comprise the suborder Pleurodira.
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