Reptiles, or members of the (Linnaean The same applies to "Linnaean name": depending on context this may either be a formal name given by Linnaeus , such as Giraffa camelopardalis Linnaeus, 1758, or a formal name in the accepted nomenclature (as opposed to a modernistic clade name)) class Reptilia, are air-breathing, generally "cold-blooded" (poikilothermic A poikilotherm is an animal whose internal temperature varies along with that of the ambient environmental temperature. Most, but not all, ectotherms are poikilothermic. The opposite of poikilothermy is homeothermy, referring to animals that maintain a constant body temperature. The term is used as a more exact description of the vernacular ") amniotes The amniotes are a group of tetrapod vertebrates that have a terrestrially adapted egg. They currently include mammals , and sauropsids (reptiles and birds), as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes. In eutherian mammals (such as humans) whose skin is usually covered in scales In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran (butterfly and moth) species, scales are plates on the surface of the insect wing, and provide coloration. Scales are quite common and have evolved multiple times with varying structure and function or scutes A scute or scutum is a bony external plate or scale, as on the shell of a turtle, the skin of crocodilians, or the feet of some birds. They are tetrapods Tetrapods are vertebrate animals having four feet, legs or leglike appendages. Amphibians, reptiles, dinosaurs/birds, and mammals are all tetrapods, and even the limbless snakes are tetrapods by descent. The earliest tetrapods radiated from the Sarcopterygii, or lobe-finned fish (either having four limbs or being descended from four-limbed ancestors) and lay amniotic eggs, in which the embryo An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination. In humans, it is called an embryo until about eight weeks after fertilization (i.e. ten weeks LMP), and from then it is instead called a fetus is surrounded by a membrane A biological membrane or biomembrane is an enclosing or separating amphipathic layer that acts as a barrier within or around a cell. It is almost invariably a lipid bilayer, composed of a double layer of lipid molecules and proteins that may constitute close to 50% of membrane content called the amnion The amnion is a membrane building the amniotic sac that surrounds and protects an embryo. It is developed in reptiles, birds, and mammals, which are hence called “Amniota”; but not in amphibians and fish , which are consequently termed “Anamniota”. The primary function of this is the protection of the embryo for its development. It stems. Modern reptiles inhabit every continent A continent is one of several large landmasses on Earth. In geography, they are identified by convention rather than any strict criterion, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia with the exception of Antarctica Antarctica (pronounced /ænˈtɑrktɪkə/ , is Earth's southernmost continent, underlying the South Pole. It is situated in the Antarctic region of the southern hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Ocean. At 14.0 million km² (5.4 million sq mi), it is the fifth-largest continent in area, and four living orders The Latin suffix -formes meaning "having the form of" is used for the scientific name of orders of birds and fishes, but not for those of mammals and invertebrates are currently recognized:

• Crocodilia 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 (crocodiles A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all members of the order Crocodilia: i.e. the true crocodiles, the alligators and caimans (family Alligatoridae) and the gharials (family Gavialidae), or even the Crocodylomorpha which includes prehistoric crocodile relatives and, gavials The gharial (Gavialis gangeticus), sometimes called the Indian gavial or gavial, is one of two surviving members of the family Gavialidae, a long-established group of crocodile-like reptiles with long, narrow jaws. It is a critically endangered species. The gharial is one of the longest of all living crocodilians, caimans, and alligators An Alligator is a crocodilian in the genus Alligator of the family Alligatoridae. The name alligator is an anglicized form of el lagarto the Spanish term for "lizard", the name by which early Spanish explorers and settlers in Florida called the alligator. There are two living alligator species: the American alligator and the Chinese): 23 species
• Sphenodontia Sphenodontia is an order of lizard-like reptiles that includes only one living genus, the tuatara . Despite its current lack of diversity, the Sphenodontia at one time included a wide array of genera in several families, and represents a lineage stretching back to the Mesozoic Era (tuataras The tuatara is a reptile endemic to New Zealand which, though it resembles most lizards, is actually part of a distinct lineage, order Sphenodontia. The two species of tuatara are the only surviving members of its order, which flourished around 200 million years ago. Their most recent common ancestor with any other extant group is with the from New Zealand New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses , and numerous smaller islands, most notably Stewart Island/Rakiura and the Chatham Islands. The indigenous Māori language name for New Zealand is Aotearoa, commonly translated as The Land of the Long White Cloud. The Realm of New Zealand also): 2 species
• Squamata Squamata, or the scaled reptiles, is the largest recent order of reptiles, including lizards and snakes. Members of the order are distinguished by their skins, which bear horny scales or shields. They also possess movable quadrate bones, making it possible to move the upper jaw relative to the braincase. This is particularly visible in snakes, (lizards Lizards are a very large and widespread group of squamate reptiles, with nearly 3,800 species, ranging across all continents except Antarctica as well as most oceanic island chains. The group, traditionally recognized as the suborder Lacertilia, is defined as all extant members of the Lepidosauria which are neither sphenodonts (i.e., Tuatara) nor, snakes Snakes are elongate legless carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with many more joints than their lizard ancestors,, and amphisbaenids The Amphisbaenia are a suborder of usually legless squamates closely related to lizards and snakes. As many species possess a pink body coloration and scales arranged in rings, they have a superficial resemblance to earthworms. They are very poorly understood, due to their burrowing lifestyle and general rarity. Most species are found in Africa ["worm-lizards"]): approximately 7,900 species
• Testudines Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield. "Turtle" may either refer to the Testudines as a whole, or to particular Testudines which make up a form taxon that is not monophyletic—see also sea turtle, terrapin, tortoise, and the (turtles Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield. "Turtle" may either refer to the Testudines as a whole, or to particular Testudines which make up a form taxon that is not monophyletic—see also sea turtle, terrapin, tortoise, and the and tortoises Tortoises or land turtles are land-dwelling reptiles of the family of Testudinidae, order Testudines. Like their marine cousins, the sea turtles, tortoises are shielded from predators by a shell. The top part of the shell is the carapace, the underside is the plastron, and the two are connected by the bridge. The tortoise has both an endoskeleton): approximately 300 species

The majority of reptile species are oviparous In most birds and reptiles, an egg is the zygote, resulting from fertilization of the ovum. To enable incubation the egg is usually kept within a favourable temperature range as it nourishes and protects the growing embryo. When the embryo is adequately developed it breaks out of the egg in the process of hatching. Some embryos have a temporary (egg-laying), although certain species of squamates are capable of giving live birth. This is achieved by either ovoviviparity Ovoviviparity , ovovivipary, or ovivipary, is a mode of reproduction in animals in which embryos develop inside eggs that are retained within the mother's body until they are ready to hatch. Ovoviviparous animals are similar to viviparous species in that there is internal fertilization and the young are born live, but differ in that there is no (egg retention) or viviparity A viviparous animal is an animal employing vivipary: the embryo develops inside the body of the mother, as opposed to outside in an egg . The mother then gives live birth. The less developed form of vivipary is called ovoviviparity, which, for instance, occurs in most vipers. The more developed form of vivipary is called placental viviparity; (birth of offspring without the development of calcified Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth most abundant element by mass in the Earth's crust. Calcium is also the fifth most abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, eggs). Many of the viviparous species feed their fetuses A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth. The plural is fetuses through various forms of placenta The placenta is an organ unique to mammals that connects the developing fetus to the uterine wall. The placenta supplies the fetus with oxygen and food, and allows fetal waste to be disposed via the maternal kidneys. The word placenta comes from the Latin for cake, from Greek plakóenta/plakoúnta, accusative of plakóeis/plakoús – πλακόε� analogous to those of mammals, with some providing initial care for their hatchlings. Extant reptiles range in size from a tiny gecko, Sphaerodactylus ariasae Sphaerodactylus ariasae, the Jaragua Sphaero or dwarf gecko, is a very small Gekkonidae species in the Sphaerodactylus genus. It is one of the world's two smallest known reptiles . The Jaragua Sphaero measures 16-18 mm from the snout to the base of the tail and can fit on a US 25-cent coin. Its range is believed to be limited to Jaragua National, that grows to only 1.6 cm (0.6 in) to the saltwater crocodile The saltwater or estuarine crocodile is the largest of all living reptiles. It is found in suitable habitats throughout Southeast Asia, Northern Australia, the Eastern coast of India and the surrounding waters. The Alligator Rivers of Northern Australia are misnamed due to the resemblance of the saltwater crocodile to alligators as compared to, Crocodylus porosus, that may reach 6 m in length and weigh over 1,000 kg. The science dealing with reptiles is called herpetology Herpetology is the branch of zoology concerned with the study of amphibians (including the frogs, toads, salamanders, newts, and gymnophionae) and of reptiles (including snakes, lizards, amphisbaenids, turtles, terrapins, tortoises, crocodilians, and the tuataras).

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