Lizards, being a suborder of the reptile class, are its largest group. These reptiles have more than 3,500 species and live on all continents except Antarctica. In this article we will consider the internal structure, skeleton, physiological characteristics of the lizard, the types and names of their families.
Interesting facts about lizards
Lizards are amazing creatures that are distinguished from the rest of the fauna by several interesting facts. The first fact is the sizes of representatives of different populations of lizards. So, for example, the smallest lizard Brukesia Mikra is only 28 mm long, while the largest representative of this group of reptiles is the Indonesian monitor lizard, aka Komodo dragon, has a body length of more than 3 meters, with a weight of about one and a half centners.
The second fact that makes these reptiles popular not only among biologists, but also ordinary people, is why and how the lizard throws off its tail. This ability is called autotomy and is a method of self-preservation. When a lizard runs away from a predator, it can grab it by the tail, which actually poses a threat to the life of a reptile. In order to save their lives, some types of medium-sized lizards are able to drop their tail, which after a while grows again. To avoid large blood loss during autotomy, the tail of the lizard is equipped with a special group of muscles that contract blood vessels.
In addition to all of the above, lizards in nature have the quality of skillful disguise, adapting to the color scheme of the environment. And some of them, especially a chameleon, can take the color of an adjacent object in a matter of moments. How does this happen? The fact is that the cells of the skin of a chameleon, which consists of several almost transparent layers, have special processes and pigment, which can be compressed or expanded under the influence of nerve impulses. At the time of the process’s contraction, the pigment collects in the center of the cell and becomes barely noticeable, and when the process is expanded, the pigment spreads throughout the cell, staining the skin in a certain color.
The skeleton and internal structure of the lizard
The body of a lizard consists of parts such as the head, neck, trunk, tail and limbs. The body is covered on the outside with a scale consisting of smaller and softer horn formations compared to fish scales, sweat glands on the skin are absent. A characteristic feature is also a long muscular organ - the language involved in the palpation of objects. The eyes of the lizard, unlike other reptiles, are equipped with a moving eyelid. Muscles are more developed than reptiles.
The lizard skeleton also has some features. It consists of the cervical, humeral, lumbar and pelvic parts that connect the spine. The lizard’s skeleton is constructed in such a way that, growing together, the ribs (the first five) form a closed sternum from below, which is a characteristic feature of this group of reptiles compared to other reptiles. The chest performs a protective function, reducing the risk of mechanical damage to internal organs, and it can also increase in volume during breathing. The limbs of the lizard, like other terrestrial vertebrates, are five-fingered, but unlike amphibians they are located in a more vertical position, which provides some elevation of the body above the ground and, as a result, faster movement. Substantial assistance in the movement is also provided by long claws, which are equipped with reptile paws. In some species, they are especially tenacious and help their master to cleverly climb trees and rocky reliefs.
The lizard skeleton differs from other groups of terrestrial representatives of the fauna by the presence in the sacral spine of only 2 vertebrae. Also a distinctive feature is the unique structure of the caudal vertebrae, namely, in the non-ossifying layer between them, due to which painless tearing off of the lizard’s tail occurs.
What are the similarities between the lizard and the newt?
Some people confuse lizards with newts - representatives of the infraorder of tailed amphibians. What are the similarities between the lizard and the newt? Representatives of these two superclasses are only similar in appearance, the internal structure of the newts corresponds to the anatomy of amphibians. Nevertheless, from the point of view of physiology, both the lizard and the newts visually look the same: a snake-like head, movable eyelids in the eyes, a long body with five-fingered limbs on the sides and sometimes with a crest on the back, a tail capable of regeneration.
Lizard feeding
The lizard belongs to cold-blooded animals, that is, its body temperature changes depending on the ambient temperature, therefore these reptiles are most active during the day when the air warms up most. Most of them are carnivorous lizards, the species and names of which include more than one thousand individuals. The production of predator lizards directly depends on the size of the reptile itself. So, small and medium-sized individuals feed on all kinds of invertebrate animals, such as insects, spiders, worms, mollusks. The victims of large lizards are small vertebrates (frogs, snakes, small birds or lizards). An exception is the Komodo lizard, which, due to its large size, can afford to hunt for larger game (deer, pigs, and even small buffalo).
Another part of the lizards belongs to herbivores that eat leaves, shoots and other vegetation. However, there are omnivorous species, such as Madagascar geckos, which eat plant foods (fruits, nectar) along with insects.
Lizard Classification
The variety of lizards is quite impressive and includes 6 superfamilies, totally subdivided into 37 families:
- Iguanas.
- Geckos.
- Skinks.
- Spindle-shaped.
- Monitor lizards
- Worm-shaped.
Each of these infra-detachments has initializing features caused by the conditions of the habitat and the intended role in the trophic chain.
Iguanoid
Iguanas are an infraorder with many varieties of life forms, in which not only the external, but often internal structure of the lizard is different. The iguaniformes include such well-known families of lizards as iguanas, agamas, and the chameleon family. Iguanas prefer a warm and humid climate, so their habitat is the southern part of North America, South America, as well as some tropical islands (Madagascar, Cuba, Hawaii, the British Virgin Islands , etc.).
Representatives of the infraorder iguanas can be recognized by the characteristic lower jaw, which is very elongated due to pleurodont teeth. A distinctive feature of iguanas is the presence on the back and tail of a prickly ridge, the size of which is usually larger in males. The iguana lizard paw is equipped with 5 fingers, which are crowned with claws (in woody species, the claws are much longer than in terrestrial representatives). In addition, iguanides have growths on their heads resembling a helmet, and throat sacs, which serve as a tool for signaling a threat, and also play a large role in mating.
The body shape of iguanas is mainly of two types:
- A tall body with clenched sides, which smoothly passes into a thickened tail. This body shape can mainly be found in individuals living on trees, for example, in the genus Polychrus in the South American habitat.
- A flattened body of a disc-shaped form - found in representatives of iguanides, living on earth.
Gecko
The gecko-like infraorder includes the chains of the chain-toed, cheshuenog, and eublefar families. The main and common feature of all representatives of this infraorder is a special chromosome set and a special muscle near the ear. Most geckos do not have a zygomatic arch, and their tongue is thick and not forked.
- The family of gecko (chain-toed) lizards has been living on Earth for more than 50 million years. The lizard skeleton and physiological features are adapted for living around the world. They have the most extensive habitat both in hot climatic zones and in temperate latitudes. The number of species of the family is more than a thousand.
- The family of Cheshuenogi is one of the legless lizards; it looks very much like snakes. You can distinguish them from snakes by the characteristic clicking sound that they are able to make to communicate with each other. The body, like that of snakes, is long, smoothly turning into a tail, which is adapted to autotomy. The head of the lizard is covered with symmetrical shields. The Cheshuenog population has 7 genera and 41 species. Habitat - Australia, Guinea and nearby land areas.
- The Eublefar family are small lizards about 25 cm long with variegated coloring, leading a nocturnal lifestyle. Carnivores, feed on insects. They live on the American, Asian and African continents.
Skink-like
Representatives of skink-like lizards are common on all continents with a temperate, tropical and subtropical climate. These are mainly land inhabitants, although there are semi-aquatic individuals, those who spend a greater period of their life on trees. This infraorder includes the following families:
- The Skinkovye family is one of the largest in its classification structure, which includes about 130 genera and more than one and a half thousand species. Distributed almost all over the world, except Antarctica. They live mainly in the tropical zone, although they are also found far from the equator. The most densely populated by this family are the islands of the Pacific Ocean, southeast Asia and Africa. Skink lizards come in different sizes, different species vary between 8-70 cm.
- The Lacertida family or Real Lizards has 42 genera and 307 species. They are adapted for living in various types of natural zones: steppes, forests, deserts, mountains and even in marshy areas. Distributed throughout Eurasia and Africa (with the exception of Madagascar). Lacertids are mostly small and medium sized lizards, but large species, such as the pearl lizard, are also found. Food - mainly carnivorous (insects, small invertebrates).
- The Theida family (11 genera, 129 species) lives in the South American continent and southern North America. The sizes of lizards range from 8 cm to 1.5 m. A characteristic feature is a bifurcated tongue like the lizards, for which they received the second name - American lizards. Curious is the fact that only females enter the population of some species, they lay unfertilized eggs, in which only females are born.
- The family Belt Tails (about 70 species) live in the arid regions of Africa. They can be recognized by a special large scale, under which there are bone plates. Large ribbed scales cover the entire back and pass to the tail region in the form of wide rings encircling the tail. Lizard cauliflowers reach a length of up to 40 cm.
- The Herrosaurus family inhabits the arid and semi-arid regions of Africa. They lead both terrestrial and semi-aquatic lifestyles. The tenacious paws allow the gerrosaurs to cleverly climb the rocks. They have a similar structure of scales with the lizards of the Skinkov family and general characteristics of the internal structure with ordinary lizards.
- The Gymnophthalmids family inhabit all of South America and the south of central America. They are among the small lizards whose adult individuals grow up to 6 cm. Hymnophthalmids live in forests and even high in the mountains, resemble the Theiids and have about fifty genera with two hundred species.
- The Night Lizards family got its name because of the way of life, during the day the lizards hide, at night they go hunting for insects and spiders. A small family (18 species) lives in arid regions in rocky terrain; the length of an adult rarely exceeds 15 cm.
Spindle-shaped lizards
The infraorder of the spindle-shaped lizards is characterized by small scales with bony plates that are not fused with each other from below. Among spindle-shaped lizards, both legless species and lizards with the usual body structure with five-fingered limbs are found. The infraorder includes three families:
- The Xenosaurus family is distinguished from other families by its developed limbs and heterogeneous scales. Emphasizes the presence of moving eyelids and auditory openings. The family includes only two genera with habitats in Central America and China.
- The spindle family has strong jaws equipped with blunt teeth. Basically, these are carnivorous lizards, born of live births. The family has about 10 genera and 80 species, living mainly on the American continent. The size of adults varies in the region of 50-60 cm.
- The legless family has only two species with habitats in Mexico and California. Differ in the absence of limbs, auditory openings and bone plates.
Ram Lizards
The Varanoid infraorder includes one genus - Varanas - and about 70 species. Lizards live in Africa, with the exception of Madagascar, Australia and New Guinea. The largest species of monitor lizards, Komodo Varan, is a record holder among all types of lizards in size, its length reaches 3 meters and its weight is more than 120 kg. His dinner could well be a whole pig. The smallest type of monitor lizard ( Short-tailed Varan ) does not exceed 28 cm in length.
Description of the monitor lizard: an elongated body, an elongated neck, limbs in a half-straightened position, the tongue is bifurcated. Lizards are the only genus of lizards in which the skull is completely ossified, open ear holes on the sides. The eyes are well developed, equipped with a round pupil and a moving eyelid. The scales on the back consists of small oval or round plates, on the belly the plates take a rectangular shape, on the head polygonal. A powerful body ends with a no less powerful tail, which lizards are able to defend themselves, inflicting strong blows to the enemy. In lizards, leading an aquatic lifestyle, the tail is used for balancing when swimming, in woody species it is quite flexible and tenacious, it helps to climb branches. Lizards differ from most other lizards in the structure of the heart (four-chamber), similar to mammals, while the heart of a lizard from other infraorders has three chambers.
Terrestrial species prevail among the monitor lizards, but there are also those that spend a lot of time in water and on trees. The body of the lizard is adapted to live in various biotopes, they can be found in the desert, and in moist forests, and on the sea coast. Most of them are predators, active in the daytime, only two species of monitor lizards are herbivorous. Various mollusks, insects, fish, snakes (even poisonous!), Birds, reptile eggs, other species of lizards become prey of carnivorous lizards, and large monitor lizards often become cannibals, eating their young and immature relatives. The entire genus of monitor lizards belongs to egg-laying lizards.
Lizards are important not only as a link in the trophic chain for their habitat, but also for anthropological activity. Thus, the skin of these lizards is used in the textile industry as a material for the manufacture of various haberdashery and even shoes. In some states, the local population eats the meat of these animals for food. In medicine, monitor blood is used to make antiseptics. And, of course, these lizards often become inhabitants of terrariums.
Vermiform lizards
The infraorder of vermiform lizards consists of one family, representatives of which are small, legless individuals that look like worms. They live on earth and lead a digging lifestyle. Distributed in the forest zone in Indonesia, the Philippines, India, China, New Guinea.