Reptiles are a fairly large group of animals, including more than 10 species.
Individuals living on Earth are the fittest and most resilient representatives of the animals that dominated the Earth before the catastrophic asteroid impact 66 million years ago.
Reptiles come in a variety of forms, including shelled turtles, large predatory crocodiles, colorful lizards and snakes. They inhabit all continents except Antarctica, the conditions of which make the existence of these cold-blooded creatures impossible.
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Reptiles include six groups of animals (orders and suborders).
These are turtles, crocodiles, snakes, amphibians, lizards and sphenodontids.
2
The first ancestors of reptiles appeared on Earth about 312 million years ago.
This was the last Carboniferous period. Both the amount of oxygen and carbon dioxide in the Earth’s atmosphere was then twice as large. Most likely, they descended from animals from the Reptiliomorpha clade, which lived in slow-moving pools and swamps.
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The oldest representatives of living reptiles are sphenodonts.
Fossils of the first sphenodonts date back 250 million years, much earlier than the rest of the reptiles: lizards (220 million), crocodiles (201.3 million), turtles (170 million) and amphibians (80 million).
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The only living representatives of sphenodonts are the tuatara. Their range is very small, including several small islands in New Zealand.
However, today's representatives of sphenodonts differ significantly from their ancestors who lived millions of years ago. These are more primitive organisms than other reptiles; their brain structure and method of movement are more similar to amphibians, and their hearts are more primitive than those of other reptiles. They have no bronchi, single-chamber lungs.
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Reptiles are cold-blooded animals, so they need external factors to regulate their body temperature.
Due to the fact that the ability to maintain temperature is lower than that of mammals and birds, reptiles usually maintain a lower temperature, which, depending on the species, ranges from 24° to 35°C. However, there are species that live in more extreme conditions (for example, Pustyniogwan), for which the optimal body temperature is higher than that of mammals, ranging from 35° to 40°C.
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Reptiles are considered less intelligent than birds and mammals. The level of encephalization (the ratio of brain size to the rest of the body) of these animals is 10% of that of mammals.
Their brain size relative to body mass is much smaller than that of mammals. However, there are exceptions to this rule. Crocodiles' brains are large relative to their body mass and allow them to cooperate with others of their species when hunting.
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The skin of reptiles is dry and, unlike amphibians, is incapable of gas exchange.
Creates a protective barrier that limits the exit of water from the body. Reptile skin may be covered with scutes, scutes, or scales. Reptile skin is not as durable as mammalian skin due to the lack of thick dermis. On the other hand, the Komodo dragon is also capable of acting. In studies of navigating mazes, it was found that wood turtles cope with them better than rats.
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As reptiles grow, they must molt to increase in size.
Snakes shed their skin completely, lizards shed their skin in spots, and in crocodiles the epidermis peels off in places and a new one grows in this place. Young reptiles that grow quickly typically shed every 5-6 weeks, while older reptiles shed 3-4 times a year. When they reach their maximum size, the molting process slows down significantly.
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Most reptiles are diurnal.
This is due to their cold-blooded nature, which causes the animal to become active when the heat from the Sun reaches the ground.
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Their vision is very well developed.
Thanks to everyday activities, reptiles' eyes are able to see colors and perceive depth. Their eyes contain a large number of cones for color vision and a small number of rods for monochromatic night vision. For this reason, the night vision of reptiles is of little use to them.
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There are also reptiles whose vision is practically reduced to zero.
These are snakes belonging to the suborder Scolecophidia, whose eyes have been reduced during evolution and are located under the scales covering the head. Most representatives of these snakes lead an underground lifestyle, some reproduce as hermaphrodites.
12
Lepidosaurs, that is, sphenodonts, and squamates (snakes, amphibians and lizards) have a third eye.
This organ is scientifically called the parietal eye. It is located in the hole between the parietal bones. It is able to receive light associated with the pineal gland, which is responsible for the production of melatonin (sleep hormone) and is involved in the regulation of the circadian cycle and the production of hormones necessary to manage and optimize body temperature.
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In all reptiles, the genitourinary tract and anus open into an organ called the cloaca.
Most reptiles excrete uric acid; only turtles, like mammals, excrete urea in their urine. Only turtles and most lizards have a bladder. Legless lizards such as the slowworm and monitor lizard do not have it.
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Most reptiles have an eyelid, a third eyelid that protects the eyeball.
However, some squamates (mainly geckos, platypuses, noctules and snakes) have transparent scales instead of scales, which provide even better protection from damage. Such scales arose during evolution from the fusion of the upper and lower eyelids, and therefore are found in organisms that do not have them.
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Turtles have two or more bladders.
They make up a significant part of the body; for example, the bladder of an elephant tortoise can make up up to 20% of the animal's weight.
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All reptiles use their lungs for breathing.
Even reptiles such as sea turtles, which can dive long distances, must come to the surface from time to time to get fresh air.
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Most snakes have only one functioning lung, the right one.
In some snakes the left one is reduced or absent altogether.
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Most reptiles also lack a palate.
This means they must hold their breath while swallowing prey. The exception is crocodiles and skinks, which have developed a secondary palate. In crocodiles, it has an additional protective function for the brain, which can be damaged by prey defending itself from being eaten.
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Most reptiles reproduce sexually and are oviparous.
There are also ovoviviparous species - mainly snakes. About 20% of snakes are ovoviviparous; some lizards, including the slow worm, also reproduce in this way. Virginity is most often found in night owls, chameleons, agamids and senetids.
20
Most reptiles lay eggs covered with a leathery or calcareous shell. All reptiles lay eggs on land, even those that live in aquatic environments, such as turtles.
This is due to the fact that both adults and embryos must breathe atmospheric air, which is not enough under water. Gas exchange between the inside of the egg and its environment occurs through the chorion, the outer serous membrane covering the egg.
21
The first representative of “true reptiles” was the lizard Hylonomus lyelli.
It lived about 312 million years ago, was 20-25 cm long and was similar to modern lizards. Due to the lack of adequate fossil material, there is still debate whether this animal should be classified as a reptile or an amphibian.
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The largest living reptile is the saltwater crocodile.
Males of these predatory giants reach a length of more than 6,3 m and a weight of more than 1300 kg. Females are half their size, but they still pose a threat to humans. They inhabit southern Asia and Australasia, where they live in coastal salt mangrove swamps and river deltas.
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The smallest living reptile is the chameleon Brookesia nana.
It is also called a nanochameleon and reaches 29 mm in length (in females) and 22 mm (in males). It is endemic and lives in the tropical forests of northern Madagascar. This species was discovered in 2012 by German herpetologist Frank Rainer Glo.
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Today's reptiles are tiny compared to reptiles of past eras. The largest sauropod dinosaur discovered to date, Patagotitan mayorum, was 37 meters long.
This giant could weigh from 55 to even 69 tons. The find was made in the Cerro Barcino rock formation in Argentina. So far, fossils have been found of 6 representatives of this species, which died in this place about 101,5 million years ago.
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The longest snake discovered by humans was a representative of Python sebae, which lives in southern and eastern Africa.
Although members of the species typically reach lengths of around 6 meters, the record holder shot at a school in Bingerville, Ivory Coast, West Africa, was 9,81 meters long.
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According to WHO, between 1.8 and 2.7 million people are bitten by snakes every year.
As a result, between 80 and 140 people die, and three times as many people have to have their limbs amputated after being bitten.
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Madagascar is a country of chameleons.
Currently, 202 species of these reptiles have been described and about half of them live on this island. The remaining species inhabit Africa, southern Europe, southern Asia up to Sri Lanka. Chameleons have also been introduced to Hawaii, California and Florida.
28
Only one lizard in the world leads a marine lifestyle. This is a marine iguana.
This is an endemic species found in the Galapagos Islands. He spends most of the day resting on coastal rocks and goes into the water in search of food. The marine iguana's diet consists of red and green algae.
