Very interesting and very unusual creatures are reptiles. The general characteristics of these creatures are very detailed. Which is not surprising, because this class of chordate land animals includes snakes, lizards, amphisbene, beak-headed, crocodiles and turtles. All of them have many distinctive features. Of course, I won’t be able to briefly talk about everything, but about the most interesting one - completely.
A bit of history
Where do reptiles come from? A general description always starts with information about it. It is logical, because it does not hurt anyone to know that terrestrial animals belonging to this class are distant descendants of dinosaurs that dominated the Mesozoic era for more than 160 million years. As you know, they became extinct about 66 million years ago. Modern reptiles can only be compared with the scattered remnants of that beautiful, mysterious ancient world.
It is also important to know that ancient reptiles are the ancestors of birds. It was they who gave rise to this group of animals, which is now actively flourishing. Scientists have long discovered that the adaptations that caused the evolution of birds were observed in their ancestors - representatives of special forms of reptiles. They were characterized by warm-bloodedness, a developed brain and an insulating cover of the body (feathers).
Cover
Now - a little more details about the anatomical specificity inherent in such creatures as reptiles. The general characteristic states that they have traits of both amphibians and higher vertebrates. What about the outer cover? Due to thickening and subsequent keratinization, it forms shields and scales. Such a cover protects the tissues and organs of the animal from the effects of external stimuli and from moisture loss.
And footless lizards and snakes scales helps to move. Due to the presence of plates, animals repel from uneven ground and move in one direction or another.
The reptiles are different. In some creatures, the flakes fit snugly together. For others, they go “overlapping”. Some even transform into crests or spikes, due to which creatures are protected from predators.
But one of the most interesting integuments can be observed in the moloch lizard (lat. Moloch horridus). She is also called the "prickly devil." Looking at the photo above, you can understand why. This small lizard that lives in the deserts of Australia has a wide and flattened body, covered with countless short curved horn spikes of various sizes. Above the eyes and on the cushioned outgrowth on the neck, they form something resembling horns. This golden brown lizard is able to change its color depending on lighting, temperature and its physiological state.
But it is worth returning to the topic of cover. Does it interfere with the growth of reptiles? No, because they periodically shed old skin. And in the process of molting, their growth occurs. And the new cover is flexible and soft. It takes time to keratinize him, and during this period these creatures hide because they are vulnerable without protection.
Skeleton structure
It is also important to mention it, if we talk about what anatomical features reptiles have. The general characteristic is very interesting, because the total number of vertebrae can reach several hundred! In an adult giant anaconda (lat. Eunectes murinus), for example, there are about 435 of them! This is impressive. But excluding snakes, the total number of vertebrae of other reptiles varies from 50 to 80.
But the structure of the axial skeleton is identical for everyone. And by the way, the division into departments is much more pronounced than in the case of amphibians. Five vertebral divisions are distinctly distinguished: cervical, trunk, lumbar, sacral and caudal. In the last of these, the maximum number of notorious vertebrae is concentrated. They have a very interesting structure: the closer to the tail, the smaller their size. The last vertebrae are quite similar in structure to tiny stick-shaped bones.
However, in some reptile groups, the skeleton has a different structure. In snakes, for example, only the trunk and tail sections are clearly visible. There is no sternum. And the vertebrae of the trunk of the turtles even merge with the shield of the shell, which is why they lose their mobility.
Skull
Also, the general characteristic of reptiles can tell a lot about the structure of the skull of these creatures. Especially about snake. Its structure evolved depending on the methods of obtaining food and the nature of nutrition.
In amphibians, for example, a short and wide skull has elongated jaws that form a very long snout. The structure of the mouth allows these creatures to capture small prey during its attack.
But in reptiles, the seizure of prey is directly related to the pursuit of the victim. And the elongated snout here has significant advantages. In addition, it is this form of jaws that allows you to tear a piece from a large prey. In crocodiles and turtles, by the way, the palatine processes form a secondary bone palate, which divides their oral cavity into the lower and upper sections. Therefore, they can breathe only by pushing the end of their heads with nostrils out of the water, because the choans (internal nasal openings) are moved back, closer to the larynx.
Muscular system
Its description also includes a general description of reptiles. The muscular system of these creatures is differentiated, represented by segmental muscles. A distinctive feature of these creatures is the intercostal muscles, which perform the most important functions during breathing.
Of particular interest is the subcutaneous musculature. In some representatives, it is so highly developed that it allows creatures to change the position of the scales. By the way, this was already mentioned in the section on cover.
The role of energy "nutrition" for the muscles of these creatures is played by anaerobic decomposition of glucose. Interestingly, most of the muscles (50-75%) can work even without oxygen saturation. Due to this, reptiles can travel small distances as quickly as warm-blooded animals. The muscles contract quickly. But if the creature “overdoes it,” then lactic acid in the muscles will begin to actively accumulate, the excess of which leads to fatigue. Therefore, representatives of this class, having made several dashes, hide for rest. In a few hours, lactic acid breaks down and the animal's strength is restored.
Muscular snakes
About her it is necessary to tell separately. The general characteristics of a reptile detachment cannot convey all its specificity. The fact is that the muscles of the snake are used to move the food swallowed by it inward, and not just for movement.
It is also important to know that there are four main types of their movement. The most famous is called serpentine, side or sliding. It is characterized by a wavy form of movement. It is this method that allows snakes to swim and reach high speeds. The record holder, by the way, is the poisonous black mamba living in Africa (Latin: Dendroaspis polylepis). Its average speed is 11 km / h.
There is also a straightforward way of movement (the technique of "caterpillars"). Snakes move forward on the skin of the abdomen, and then pull the entire back of the body. In the third method, called parallel, the animal as if casts itself to the side (side cycle of movement). To see this is a rarity. This method is characteristic of snakes living on loose sand in deserts.
The fourth method is no less rare. It is called "concertina. Or, in other words, the accordion technique. It is used when moving a snake in a tree. It looks unusual, because the body is supposedly going to form horizontal loops, after which the head rushes forward, due to which the "accordion" is straightened.
All this is very unusual, but it explains the external structure and skeleton of reptiles. The general characteristic, of course, helps to approximately understand what it is “from the inside”, but after observing the movements described above, one can visualize everything.
Nervous system
It is also important to mention it when talking about the Reptiles class. The general characteristics of the nervous system are detailed. But before discussing it, it is worth noting that the central nervous system of these creatures is represented by the spinal cord and the brain, which consists of five departments.
The first is the front. It is from his hemispheres that the olfactory lobes depart.
The second is intermediate. In its lower part is the pituitary gland, and in the upper part - the pineal gland. It is next to it, by the way, that the hatteria (the only modern representative of the order of beakheads) and lizards develop an unpaired photosensitive organ called the parietal eye. And crocodiles, by the way, have neither a pituitary gland, nor an pineal gland.
The third division is called the middle. It is represented by visual lobes. In this regard, the Reptiles class also distinguished itself. The general characteristic allows us to understand that their middle section and the visual cortex are much more developed than amphibians. The last component of the brain is the cerebellum. And another oblong section.
However, this is not all that is worth knowing about the Reptiles class. General description, in short, makes it clear that representatives of this category of animals are distinguished by a developed physiological and anatomical structure. But it is also important to know that in their spinal cord the separation into gray and white matter is much more clearly noticeable, in contrast to the same amphibians. And they also have a pronounced parasympathetic and sympathetic autonomic nervous system. It is represented by a chain of paired nerve clusters (ganglia).
Sight and sense of smell
This is perhaps the most interesting topic. And the general characteristic of reptiles (or reptiles) will be incomplete without mentioning it.
So these beings have six sense organs. The first is sight. Interestingly, many lizards distinguish colors perfectly. Shades are the most important means of their communication. They recognize poisonous insects by their color. And giant turtles are also capable of perceiving colors. Many of them respond well to red. There is even a hypothesis that turtles are able to perceive infrared light.
Snakes and crocodiles do not distinguish colors. But in reptiles, the eye has the same structure as in humans. And some of their representatives have eyelids. Moreover, the lower ones are more mobile than the upper ones. Pupils, by the way, differ in reptiles. Representatives leading a nocturnal or twilight lifestyle, it is vertical. And in geckos on narrowed pupils, you can even see point holes that focus on the retina as an independent image. This feature provides maximum sharpness displayed for the lizard reality.
As for the sense of smell. The general characteristics of reptiles can also tell about its specificity. In short, chemoreceptors play a major role in the sense of smell of these creatures. Due to them, these animals perceive smell very well. They are able to find food buried at a depth of up to 8 centimeters. Vipers, snakes and monitor lizards, due to their sense of smell, can determine the appearance of an approaching animal long before it appears in the field of view. And crocodiles, lizards and turtles do have special glands, the secret of which is intended to “signify” the occupied territory. By odorous substances, these creatures mark their sites.
Lifestyle
The general characteristic of reptiles can also tell about it. Grade 7 - approximately at this stage in high school this topic is being studied.
So, the vast majority of animals belonging to this class are carnivores. Reptiles mainly feed on carrion and insects. But real predation is characteristic only of some lizards, crocodiles and snakes. Iguanas and agamas can eat anything - from vegetables and fruits to animal meat. However, there are exclusively herbivorous creatures. These include land turtles.
Interestingly breeding occurs. It is important to mention it when talking about the Reptiles (or Reptiles) class. The general description briefly explains how everything happens.
So, fertilization is internal. The embryo develops when it is in an egg, which is covered with either calcareous or leathery shell. Egg production is also found. Very rarely, cubs are born, like viviparous animals. It is worth noting that the care of the offspring is characteristic of these creatures. Female crocodiles, for example, carefully transfer their babies in the oral cavity from masonry to ponds.
It’s also interesting to know that the vast majority of reptiles do not have a voice apparatus. They can publish nothing but a whistle or hiss. So no marital cries can be heard - these creatures are guided by the smell. Only eublefar lizards are able to squeak.
Interesting representatives
Well, the general characteristics and features of the external structure of reptiles were considered above. Finally, we can talk about some rare representatives.
The smallest creature of this class is the squeaky gecko living in deserts and semi-deserts. You can meet him in areas where the Volga flows. This is an amazing creature covered with granular scales. The length of his body reaches only 41 mm! He has about the same tail, which is easily discarded.
Gyurza, which is the largest representative of the genus of giant vipers, is also noteworthy. This is a poisonous creature weighing 3 kilograms, whose length reaches 2 meters.
But with the king cobra, of course, gyurza cannot be compared. After all, this is the largest poisonous snake. Some individuals reach a length of 5.6 m. By the way, they grow throughout life. And they live up to 30 years.
A snake such as the taipan McCoy is very attractive. That's just a beautiful creature with golden black scales is very dangerous. After all, this is the most poisonous land snake in the world. The poison of one individual (44 mg) is enough to kill a quarter of a million mice or 100 people.
This, of course, is far from all the amazing creatures that reptiles (or Reptiles) class replete with. The general characteristic allows us to understand how great their diversity is. But it is also worth noting the attention of the Far Eastern skink. This is a lizard that can be found in Japan or on the Kuril Islands. She, like all the previously listed species, is listed in the Red Book of Russia. And its highlight is an amazing color that can be appreciated by looking at the above photo.
Well, you can still talk about this topic for a long time. After all, the world knows 9,400 species of reptiles, and each of them is unique in its own way. But they can be found on an individual basis. Everything that was said above may well arouse interest in this.