include snakes, lizards, , and many kinds extinct, such as the famous . The first reptiles appeared in excellent, during .
Many forms have arisen and developed throughout, age of reptiles. Since then, the vast majority came out. Among the modern forms of reptiles, there are about 2500 species of snakes, 2500 species of lizards, about 250 species of turtles and 21 species of .
Found throughout the temperate and tropical regions of the world, they are “cold-blooded” animals, or(them be close to the environment when the animal is sleeping or at rest). They have four limbs, with the exception of snakes and some lizards (such as slowworms). They have lung breathing. Their skin is covered with scales, which is the main sign of their belonging to this ancestral group.
Turtles: egg-laying reptiles
All reptiles, due to the presence of a copulatory organ in the male. Most reptiles are (they lay eggs) but many snakes and lizards (eggs hatch in the womb, which gives birth to already developed young), especially species from cool regions. Modern reptiles are characterized by the development of two embryonic membranes: defender and respiratory, vascular membrane. All reptiles have an amnion. and , prevents the eggs from drying out; early stages of the animal life cycle that do not depend on water, this characteristic allowed reptiles to completely free themselves from the aquatic environment for their reproduction (even in marine species such as which will lie on the ground).
Thus, turtles are recognizable as reptiles by the bony shell that covers their internal organs. Turtles are primitive reptiles whose oldest fossils date back to the Triassic period, about 200 million years ago. Therefore, their appearance preceded the appearance. However, turtles continue to adapt and evolve to the present day.
Turtles belong to the orderfrom the class of reptiles. This species is divided into two suborders: cryptodera, turtles, in which the head enters the shell by retracting the neck, and pleurodes, animals that retract the head by lateral flexion of the neck (species ).
This detachment has already separated from other reptiles in. Today it brings everything together and water. Some species have flat wide ribs on which a shell of horn or parchment scales rests.
In total, there are about two hundred and fifty species, grouped into nine families. Most species inhabit only temperate or tropical regions and are adapted to freshwater or terrestrial habitats.
The carapace is in two parts: the carapace and the plastron.
The size of turtles is extremely variable, from 15 cm to 2.5 meters. The dorsal part of the turtle, under which it can more or less completely fold its head, legs and tail, is called the shell. The abdominal flat part is called the plastron. Both parts are connected to the vertebrae and ribs. The structure and size of the carapace and plastron vary depending on the species, evolution of behavior and lifestyle of the animal.
The tortoise shell is made up of two layers: an inner bony layer made up of scales and an outer stratum corneum made up of ridges. Although in some species the shell is hard and rather thick, it is surprisingly sensitive due to the manywhat it contains. The scales of this shell and plastron are arranged in several rows and have specific names (vertebral, dorsal, cervical, costal, marginal, axillary, etc.).
Turtles are toothless but equipped with an efficient horny beak. They dont have. heart as in with the exception of crocodiles, has three cavities, but functions almost as if it had four.
Few turtle species live exclusivelyWhere ; however, turtles are essentially while aquatic species are mostly carnivorous. All turtles lay and bury their eggs in burrows. As a rule, they are long-lived, with some species can live for more than a hundred years (giant tortoises, in particular or Aldabra).