The leatherback turtle (Dermochelys coriacea) is the largest of all living sea turtles The superfamily Chelonioidea has a worldwide distribution; sea turtles can be found in all oceans except for the polar regions.[citation needed] Some species travel between oceans. The Flatback turtle is found solely on the northern coast of Australia and the fourth largest modern reptile Reptiles, or members of the class Reptilia, are air-breathing, generally "cold-blooded" amniotes whose skin is usually covered in scales or scutes. They are tetrapods (either having four limbs or being descended from four-limbed ancestors) and lay amniotic eggs, in which the embryo is surrounded by a membrane called the amnion. Modern behind three crocodilians Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period (Campanian stage). They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria. Members of the crocodilian stem group, the clade Crurotarsi, appeared about 220 million years ago in.[2][3] It is the only living species There are many definitions of what kind of unit a species is . A common definition is that of a group of organisms capable of interbreeding and producing fertile offspring of both genders, and separated from other such groups with which interbreeding does not (normally) happen. Other definitions may focus on similarity of DNA or morphology. Some in the genus Dermochelys. It can easily be differentiated from other modern sea turtles by its lack of a bony Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue. Because bones come in a variety of shapes and have a complex internal and external structure shell An exoskeleton is an external skeleton that supports and protects an animal's body, in contrast to the internal endoskeleton of, for example, a human. Some animals, such as the tortoise, have both an endoskeleton and an exoskeleton. In popular usage, many of the larger kinds of exoskeletons are known as "shells". Instead, its carapace A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron is covered by skin and oily flesh. Dermochelys coriacea is the only extant Extant is a term commonly used in biology to refer to taxa that are still in existence (living). The term extant contrasts with extinct. For example, Brandt's Cormorant is an extant species, while the Spectacled Cormorant is an extinct species. Likewise, of the group of molluscs known as the cephalopods, there are approximately 600 extant species member of the family What does and does not belong to each family is determined by a taxonomist. Similarly for the question if a particular family should be recognized at all. Often there is no exact agreement, with different taxonomists each taking a different position. There are no hard rules that a taxonomist needs to follow in describing or recognizing a family Dermochelyidae. Instead of teeth, the leatherback turtle has points on the tomium of its upper lip, with backwards spines in its throat to help it swallow food. Leatherback turtles can dive to depths as great as 4,200 feet (1,280 metres).[4]
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