What are Reptiles?

They are cold-blooded vertebrate animals, covered in scales and with lung breathing (breathing air). The word Reptil comes from Reptar which means that they crawl along the ground, but as we will see later, not all of them crawl. Let’s explain all this a little more.

Characteristics of reptiles

They are cold-blooded , because they can not regulate their own body temperature and their temperature depends on the environment and their bodies react to the temperature of their environment. When they get too hot, they can get into the water or get in the shade to cool off. When it’s too cold they can hang out in the sun to warm up.

The scales  or plates that cover its surface form a kind of armor that helps prevent the loss of water through your skin and protects your body. They can be hard or soft. The skin of the Reptiles is completely dry, it appears with scales in the lizards and snakes, with plates or horny shells in the turtles and with skeleton gouges in the crocodiles and alligators.

They breathe in almost the same way as humans, inhale and exhale through their lungs. Some reptile Species may be able to help themselves breathe through different means, such as permeable skin for gaseous exchange like water turtles, but all reptiles have to breathe through their lungs to survive.

Not all reptiles crawl, most reptiles have legs (4 legs) and can move from one place to another without crawling. What is certain is that all reptiles have their limbs (legs) very short and sometimes give the feeling of crawling.

In addition, most reptiles are oviparous , that is, they are born from eggs.

The main categories are snakes, turtles and crocodiles, alligators and gharials. There are some 8,240 different species that can be found on all continents except Antarctica.

Reptiles use a variety of methods to defend themselves from dangerous situations, such as avoidance, camouflage, sibilant and biting.

Types of reptileS

There are 4 types of reptiles

1. Rhynchocephalia : Tuatara.
2. Squamata: Snakes and Lizards
3. Chelonia: Turtles and Tortoises
4. Crocodilia : Crocodiles and Caiman

1. The order Rhynchocephalia

:has a single living member, the tuatara, a reptile lizard from New Zealand. 

Characteristics

It is an order of reptile type lizard that includes a single living species of tuatara, which in turn has two subspecies (Sphenodon punctatus punctatus and Sphenodon punctatus guntheri), which only inhabit parts of New Zealand . Despite its current lack of diversity, the Rhynchocephalia at one time included a wide range of genera in several families and represents a lineage that dates back to the Mesozoic Era. Many of the niches occupied today by lizards were occupied by spherodontians. There were even several successful aquatic spheroid groups such as the pleurosaurs and the stranger.

Sphenodonts, and its sister group Squamata (which includes lizards, snakes and amphisbaenians), belong to the supercomputer Lepidosauria, the only surviving taxon within Lepidosauromorpha. Squamates and sphenodontia show a caudal autotomy (loss of the tip of the tail when threatened) and have transverse cloacal clefts. The origin of the fenodontes is probably found near the division between the Lepidosauromorpha and the Archosauromorpha. Although they resemble lizards, the similarity is superficial, because the group has several unique characteristics among reptiles. The typical form of lizard is very common for the first amniotes; The oldest known fossil of a reptile, the Hylonomus, resembles a modern lizard.

The Tuatara resembles the form of modern lizards with a robust body, which we could call iguanas, this resemblance is further intensified by a row of thorns on the back, dark olive-colored, the sides dotted with pale spots. the pupil, the large specimens are two and a half feet long, although the superficial resemblance could group this reptile with lizards, its skeleton and anatomy show that it belongs to a different part of a technical classification. “A unique characteristic of Tuatara is a “third eye” on the top of the head. The “eye” has a retina, lens and nerve endings, but it is not used to see. The single eye is sensitive to light and is believed to help the tuatara judge the time of day or the season. Further, It has two parallel rows of teeth in its upper jaw, and the space between these rows is where the teeth of the lower jaw are adjusted to perform a special grinding / crushing movement to crush the prey. In addition, the tuatara has a diapsid skull but lacks a complete lower temporal bar that separates it from other species, as well as its acrodont teeth and a pair of protruding incisor teeth. The tooth shape was originally designed for a strictly insectivorous diet with penetrating teeth. Later, the teeth were diversified to several ancestors of the tuatara that included herbivores, carnivores and omnivores. The teeth were complex enough to crush crab shells while others maintained continuous growth in the lower jaw for the decomposition of plant material. Its current dental structure is specialized in crushing prey after its capture. The fossil record shows that the tuatara lineage separated from the squamatos 250 million years ago

2. The order Squamata

:includes lizards (Suborder Sauria) and snakes (Suborder Serpentes). Almost all the members of this class are terrestrial. 

Characteristics

The order of the scaly reptiles (scientifically known as Squamata) is composed of six sub orders:

• Blind snakes (Amphisbaenia)
• Autarchoglossa (Suborder composed of 13 families with a total of 405 species and subspecies of lizards, lizards, varanids)
• Gekkota (Suborder composed of 7 families with a total of 1550 species and subspecies of lizards)
• Iguania (Suborder composed of 14 families with a total of 2642 species and subspecies of lizards)
• Snakes (Serpentes or Ophidians)

The reality is that all reptiles of the scaly order share an evolutionary history although they have very different sizes, colors, shapes or characteristics and according to the taxonomic institute to date there are 9,974 species and subspecies included within the scaly reptiles.

Squamous suborders containing lizards

It is really difficult to understand the taxonomic classification of these reptiles, but we will continue to clarify concepts. Of the six scaly subspecies only in three of them could be considered that there are lizards (the word lizard is a diminutive of lizard), the suborder of the Autarchoglossa, the Gekkotas and the Iguanas.

Autarchoglossa

Composed of 13 families that belong to the suborder of the Autarchoglossa some of them can not be considered lizards, for example the varanids that are about lizards of considerable size or the so-called glass lizards that despite being lizards, lack of limbs they make them look more like snakes.

However, in this group is included the family Lacertidae which is perhaps the best known family of all lizards.

Some species of lizards, such as the collared lizard or the rock lizard , are just a couple of examples of the reptiles that belong to this family.

Gekkotas

The vast majority of the 1,550 species cataloged today if you can consider lizards, both by size and by concepts, of the three suborders of the Gekkotas is undoubtedly the one that includes more species encompassed in this group there are well-known specimens like the dragon lizard , or the Tokay gecko .

Iguanas

In the suborder of the iguanas you can find the chameleons, iguanas and pogona, but there are some species of these families of reptiles that are really big and could not be classified as small lizards, however it is in this group that the reptile is found. small of the world, which is none other than the chameleon known as Brookesia micra, although the chameleons maybe could not be considered lizards instead the pogona vitticeps  if it is encompassed in this group

3. The members of the order Crocodilia 

:which includes crocodiles, alligators, and gavials, are large carnivorous reptiles, swamps and tropical and subtropical rivers. They constitute the only remaining class of the great subclass of reptile Archosauria, which includes the extinct dinosaurs. 

Characteristics

The Crocodilia or Crocodylia order groups together the larger animals that comprise the Reptilia class . Its origins date back to the Triassic period, although of the different families that have existed only three are conserved: gaviálidos (gaviales),  aligatóridos (alligator and alligators) and crocodilians (crocodile).

Morphologically crocodiles have a series of common characteristics, such as having a powerful and powerful tail that enables you to swim with agility; his body is covered with very hard scales, thanks to the keratin becomes a powerful frame, which provides the crocodile with excellent protection. They have a heart with four chambers, unlike most reptiles that comprise the Reptilia class, in which their heart is divided into three chambers, they also have very powerful jaws and their teeth move their lifelong, The best known They are the  crocodile or the alligator itself.

They are reptiles that prefer to inhabit areas of fresh water, however there are specimens that occasionally also move to brackish guts. They feed on vertebrate and invertebrate animals, hunt regularly and voraciously consume their prey.

The reproduction is oviparous, they put the eggs in cavities that the female builds, normally the brood is covered with weeds and vegetation, since its further decomposition favors the incubation process.

They spend most of their time submerged in the water, when they move to the land, their movements are slower and they walk dragging the ventral area.

The population has suffered a considerable decline, mainly due to the destruction of habitat and poaching for the commercialization of the skins, thanks to conservation programs and legal protection of the species, it has been possible to maintain and conserve the families that we know nowadays.

Morphological differences

The three existing crocodile families are mainly differentiated by a series of morphological features, so we have:

Gavialidae

The gavialidae are easily recognizable since it presents / displays a very pronounced snout.

Alligatoridae

Alligator and alligators,  the upper teeth remain more displaced than the lower ones, since these animals have a wide jaw, so that the teeth are not visible when they remain with the mouth closed.

Crocodiles

Crocodile , placement of the teeth in the form of a row, for that reason the fourth lower tooth is visible when the jaws are kept closed.

4. The turtles, order Chelonia

:have a shell of bony protection, usually covered with horny plates. They are mostly aquatic, although some are adapted to the land. They are the oldest reptiles, practically unchanged since the Triassic period.

to which the turtles belong, is divided into two suborders: the first, which includes species capable of retracting the head inside the shell with a Telescope movement of the neck , and a second comprising the species that hide the head bending the neck to the side. The order has a total of about 270 living species grouped into 12 or 13 families.

They live on all continents, except Antarctica, and can be found in a wide variety of habitats, from lagoons , rivers and seas to forests and meadows and even in deserts . Like the rest of the reptiles, the turtles are ectothermic animals, that is, their body temperature depends on the environment. This makes turtles more abundant in tropical and subtropical areas.

Characteristics

The characteristic feature of turtles is their carapace, which consists of an inner bony layer and, in many cases, an outer layer covered with large scales called shields. All the internal organs of the turtles have adapted to function within this unique armor.

The turtles have very variable sizes, from the box turtle of North America, of about 15 cm in length, to the gigantic leatherback turtle, a marine animal that can reach a length of about 2.4 m and can weigh up to 900 kg. The upper part of the carapace or shell of the turtles, under which the head and limbs can be collected to a greater or lesser extent, is called a carapace or back. The lower part of the carapace, flat, is called plastron. The two-part shell is attached to the vertebrae and ribs; the structure and size of the back and the plastron varies from one species to another. The different species also exhibit adaptive changes in their behavior and way of life.

The body of the turtles is wrapped in a shell formed by a series of bony plates covered by a horny shield. The vertebrae and ribs are fused inside the shell, reinforcing it. The aquatic turtles have a flatter shell than the land turtles that present it with a vaulted form.

The typical carapace of a turtle is formed by two layers: an inner bony, whose sections are called plates, and a corneal upper layer (of keratin), formed by the so-called shields. Although it is hard, and sometimes considerably thick, the shell of the turtles is a very sensitive structure due to the large number of nerve endings that it contains. The horny outer layer of some turtles, especially that of the hawksbill turtle, has been used in the manufacture of ornamental objects.
The bones of the turtle’s skull are immovable connected. The animal lacks teeth, although in the soft-shelled turtles traces of them have been detected during the embryonic phase, but the jaws hold horny plates that they use to chew the food. It also lacks sternum. The heart , like that of the other reptiles, with the exception of the crocodiles , has three chambers, but acts as if it had four due to the presence of an incomplete partition in the ventricle. Breathing is done with the help of the abdominal and pectoral muscles since, living inside a rigid shell, they can not expand the chest to help in breathing

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