Lizards, being a suborder of the class of reptiles, are its most numerous group. These reptiles number 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, species and names of their families.
Interesting facts about lizards
Lizards are amazing creatures, which are distinguished from the rest of the fauna by several interesting facts. The first fact is the size of representatives of different populations of lizards. So, for example, the smallest lizard, Brookesia Micra, is only 28 mm long, while the largest representative of this group of reptiles, the Indonesian monitor lizard, also known as the Komodo dragon, has a body length exceeding 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 among ordinary people, is why and how the lizard drops its tail. This ability is called autotomy and isself-preservation method. When a lizard runs away from a predator, he can grab her by the tail, which actually poses a threat to the life of the reptile. In order to save their lives, some species of medium-sized lizards are able to shed their tail, which grows again after a while. To avoid large blood loss during autotomy, the tail of the lizard is equipped with a special muscle group that reduces blood vessels.
In addition to all the above, lizards in nature have the quality of skillful disguise, adapting to the color scheme of the environment. And some of them, especially the chameleon, can take on the color of an adjacent object in a matter of moments. How does this happen? The fact is that the skin cells of a chameleon, consisting of several almost transparent layers, have special processes and pigment, which, under the influence of nerve impulses, can shrink or expand. At the moment of contraction of the process, the pigment gathers in the center of the cell and becomes barely noticeable, and when the process is unclenched, the pigment spreads throughout the cell, staining the skin in a certain color.
The skeleton and internal structure of a lizard
The body of a lizard consists of such parts as the head, neck, torso, tail and limbs. The body is covered with scales on the outside, consisting of smaller and softer horn formations compared to fish scales, there are no sweat glands on the skin. A characteristic feature is also a long muscular organ - the tongue, which is involved in feeling objects. The eyes of a lizard, unlikeother reptiles are equipped with a movable eyelid. Musculature has a greater degree of development than that of reptiles.
The lizard skeleton also has some features. It consists of the cervical, shoulder, lumbar and pelvic regions, which are connected by the spine. The skeleton of the lizard is built in such a way that, when fused, 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 those of 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. Significant assistance in movement is also provided by the long claws with which the paws of the reptile are equipped. In some species, they are especially tenacious and help their master to deftly climb trees and rocky terrain.
The skeleton of a lizard differs from other groups of terrestrial representatives of the fauna by the presence of only 2 vertebrae in the sacral spine. Also, a distinctive feature is the unique structure of the tail vertebrae, namely in the non-ossifying layer between them, due to which the lizard's tail is painlessly torn off.
What are the similarities between a lizard and a newt?
Some people confuse lizards with newts - representatives of the infraordertailed amphibians. What are the similarities between a lizard and a newt? Representatives of these two superclasses are similar to each other only externally, the internal structure of newts corresponds to the anatomy of amphibians. Nevertheless, from the point of view of physiology, both lizards and newts visually look the same: a snake-like head, movable eyelids on 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 food
The lizard belongs to cold-blooded animals, that is, its body temperature changes depending on the ambient temperature, so these reptiles are most active during the day, when the air warms up the most. Most of them are carnivorous lizards, the species and names of which include more than one thousand individuals. The prey of predatory 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 medium-sized vertebrates (frogs, snakes, small birds or lizards). The exception is the Komodo monitor lizard, which, due to its large size, can afford to hunt larger game (deer, pigs, and even medium-sized buffaloes).
Another part of the lizards is herbivorous, eating leaves, shoots and other vegetation. However, there are also omnivorous species, such as Madagascar geckos, which eat plant foods (fruits, nectar) along with insects.
Classification of lizards
The variety of lizards is quite impressive and includes 6 superfamilies, in totalsubdivided into 37 families:
- Iguanas.
- Geckos.
- Skinks.
- Spindle-shaped.
- Varana.
- Wormoid.
Each of these infraorders has initializing features, determined by the habitat conditions and the intended role in the food chain.
Iguanas
Iguanas are an infraorder with many varieties of life forms, which differ not only in the external, but often in the internal structure of the lizard. Iguana likes include such well-known families of lizards as the iguana, agamo and 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 strongly elongated lower jaw due to pleurodont teeth. Also, a distinctive feature of iguanas is the presence of a spiny crest on the back and tail, the size of which is usually larger in males. The paw of the iguana lizard is equipped with 5 fingers, which are crowned with claws (in arboreal species, the claws are much longer than those of terrestrial representatives). In addition, iguanas have helmet-like growths on their heads and throat pouches that serve as a threat signaling tool and also play a large role in mating.
The body shape of iguanas is predominantly of two types:
- Tall body withcompressed sides, which smoothly turns into a thickened tail. This body shape is mainly found in tree-dwelling individuals, such as the genus Polychrus in the South American range.
- A flattened disc-shaped body - found in representatives of iguanas living on the ground.
Geckos
The gecko-like infraorder includes the families Cepkopale, Scale-footed and Eublepharidae. 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 (grasped-toed) lizards has been living on Earth for more than 50 million years. The lizard's skeleton and physiological features are adapted for living all over 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 Scalefoot family is one of the legless lizards, outwardly very reminiscent of 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 for autotomy. The head of the lizard is covered with symmetrical shields. The population of Cheshuenogs includes 7 genera and 41 species. Habitat - Australia, Guinea and nearby land areas.
- The Eublepharidae family are small lizards about 25 cm long with a variegated coloration, leading a nocturnal lifestyle. Carnivores, eatinsects. They live on the American, Asian and African continents.
Skinks
Representatives of skink lizards are distributed on all continents with a temperate, tropical and subtropical climate. These are mainly land dwellers, although there are also semi-aquatic individuals, those who spend a greater period of their lives on trees. This infraorder includes the following families:
- The Skink family is one of the most numerous in terms of classification structure, which includes about 130 genera and more than one and a half thousand species. They are distributed almost all over the world, except for Antarctica. They live mainly in the tropical zone, although they are also found far from the equator. The islands of the Pacific Ocean, Southeast Asia and Africa are most densely populated by this family. Skink lizards come in different sizes, different species vary between 8-70 cm.
- The family of Lacertida or Real Lizards has 42 genera and 307 species. They are adapted to living in various types of natural areas: steppes, forests, deserts, mountains, and even in swampy areas. Distributed throughout Eurasia and Africa (with the exception of Madagascar). Lacertids are mostly small to medium sized lizards, but there are also large species such as the pearl lizard. Food is predominantly carnivorous (insects, small invertebrates).
- The Teyida family (11 genera, 129 species) lives in the South American continent and the southern partNorth America. The sizes of lizards range from 8 cm to 1.5 m. A characteristic feature is a forked tongue like that of monitor lizards, for which they received a second name - American monitor lizards. It is curious that the population of some species includes only females, they lay unfertilized eggs in which only females are born.
- Girdletail family (about 70 species), live in arid regions of Africa. They can be recognized by their special large scales, 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 clasping the tail. Belt-tailed lizards reach up to 40 cm in length.
- Family Herrosaurs inhabit arid and semi-arid regions of Africa. They lead both terrestrial and semi-aquatic lifestyles. Tenacious paws allow herrosaurs to deftly climb rocks. They have a similar scale structure with Skink lizards and common internal structure characteristics with Common lizards.
- Family Gymnophthalmids inhabit all of South America and south of Central America. They are among the small lizards, whose adults grow up to 6 cm. Gymnophthalmids live in forests and even high in the mountains, have an outward resemblance to Teiids and number about fifty genera with two hundred species.
- The Night Lizard 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 15see
Spindle Lizards
The infraorder of fusiform lizards is characterized by small scales with bone plates not fused together from below. Among the spindle-shaped lizards, there are both legless species and lizards with the usual body structure with five-fingered limbs. The infraorder includes three families:
- The Xenosaur family differs from other families in its developed limbs and heterogeneous scales. Highlights the presence of movable 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 that reproduce by live birth. The family includes about 10 genera and 80 species, living mainly on the American continent. The size of adults ranges from 50-60 cm.
- The Legless family has only two species with a habitat in Mexico and California. They are distinguished by the absence of limbs, auditory openings and bone plates.
Monkey Lizards
The infraorder Varaniformes includes one genus - Monitor lizards - and about 70 species. Monitor lizards live in Africa, with the exception of Madagascar, Australia and New Guinea. The largest species of monitor lizards, the Komodo monitor lizard, is a real champion among all types of lizards in size, its length reaches 3 meters and its weight is more than 120 kg. His supper could very well be a whole pig. The smallest species of monitor lizards (Short-tailed Monitor) is notexceeds 28 cm.
Description of the monitor lizard: an elongated body, an elongated neck, limbs in a semi-straightened position, a forked tongue. Monitor lizards are the only genus of lizards in which the skull is completely ossified, there are open ear holes on the sides. The eyes are well developed, equipped with a round pupil and a movable eyelid. The scales on the back consist of small oval or round plates, on the belly the plates take a rectangular shape, on the head they are polygonal. A powerful body ends with a no less powerful tail, with which monitor lizards are able to defend themselves, inflicting strong blows on the enemy. In aquatic lizards, the tail is used to balance when swimming; in arboreal species, it is quite flexible and tenacious, helping to climb branches. Monitor lizards differ from most other lizards in the structure of the heart (four-chambered), similar to mammals, while the heart of a lizard from other infraorders has three chambers.
In terms of lifestyle among monitor lizards, terrestrial species predominate, but there are also those that spend a lot of time in the water and on trees. The body of the lizard is adapted to living in various biotopes, they can be found in the desert, and in humid forests, and on the sea coast. Most of them are predators, active during the daytime, only two species of monitor lizards are herbivores. Various mollusks, insects, fish, snakes (even poisonous!), birds, reptile eggs, other types of lizards become prey for carnivorous lizards, and large monitor lizards often become cannibals, eating their young and immature relatives. Wholethe genus of monitor lizards belongs to oviparous lizards.
Monitor lizards are important not only as a link in the food chain for their habitat, but also for anthropological activities. 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 lizard blood is used to make antiseptics. And, of course, these lizards often become inhabitants of terrariums.
Worm Lizards
The infraorder of worm-like lizards consists of one family, the representatives of which are small, legless individuals, outwardly similar to worms. They live on the ground and lead a burrowing lifestyle. Distributed in the forest zone in Indonesia, the Philippines, India, China, New Guinea.
