Vertebrate Zoology: A Study Guide - T. A. Dauda 2014

Metazoans
Class Reptilia, or Reptiles
Order Squamata

There are over 5,500 known species of squamate reptiles, which include lizards, chameleons, and snakes. Their Morphology and appearance vary significantly. However, all members of the order share common features: their bodies are covered with horny scales of various Sizes and Shapes, their Teeth are fused to the jawbones, and their cloaca appears as a transverse slit. The order is divided into three suborders: Lizards (Sauria), Chameleons (Chamaeleontes), and Snakes (Serpentes).

Suborder Lizards (Sauria). The total number of lizard species reaches up to 2,500. Most of them have a moderately elongated body with a clearly defined neck and a long, flexible tail. In a significant number of species, the limbs are well developed, though their shape varies. In a few representatives, the legs are entirely absent or underdeveloped (e.g., slowworms, Glass lizards). In appearance, such lizards resemble snakes, yet most of them retain limb girdles. The BONES OF THE upper jaw in lizards are rigidly attached to the Skull, and the left and right halves of the lower jaw are fused together. Movable eyelids and an externally visible tympanic membrane are usually present. Many species possess The ability to detach a part of their tail (autotomy). After detachment, the tail regenerates, but its Skeleton does not ossify. Lizards are very widely distributed. Most inhabit the tropics, but some range as far as the Arctic Circle. In mountainous regions, certain species ascend to altitudes of up to 4,000 m. Some lead a semi-arboreal lifestyle. Aquatic forms are few, such as marine iguanas.

True lizards are slender, small- to medium-sized animals. Their pentadactyl limbs are well developed, and their tails are fragile. The greatest number of species inhabits steppes, deserts, and foothills. In the forest belt, they prefer areas with dry, well-warmed soil. The only exception is the viviparous lizard, which is widespread in our country in shaded forests, often on damp, moss-covered soil. This is the only lizard species that crosses the Arctic Circle.

In the temperate zone of our country, the sand lizard (or nimble lizard) is widespread. It inhabits forests, gardens, groves, and woodlands, preferring dry, sun-warmed locations. It lives in burrows, rarely venturing farther than 15–20 m from them. It hibernates during the winter and can tolerate cooling down to -5...-7°C. As the air and soil warm up, the lizard returns to active life. In spring, it lays eggs in dry, sun-warmed places (in sand, moss, or under fallen leaves). From late July through almost the entire August, tiny lizards hatch, capable of independent survival. The diet of the sand lizard consists primarily of various insects and slugs. Within a day, a single individual can destroy up to 70 invertebrates, many of which are agricultural pests. Therefore, lizards are beneficial animals and must be protected. In Ukraine and the Caucasus, the green lizard—closely related to the sand lizard but larger—can be found.

Slowworms form numerous transitional forms ranging from those with well-developed limbs to legless ones that externally resemble snakes. Most species are distributed in North America, while a few inhabit South America, Europe, and Southeast Asia. Two legless species are found in our country: the common slowworm (or blindworm), up to 26 cm long, and the sheltopusik. The slowworm has a coppery coloration and is widespread in the forests of the European part of Russia, excluding the North. It reproduces via viviparity. The sheltopusik is olive-yellow and reaches up to 1 m in length; it is found in Crimea, the Caucasus, and Central Asia, inhabiting dry steppes, often along ravine slopes. It reproduces by laying eggs. Both the slowworm and the sheltopusik are beneficial to humans, as they destroy numerous agricultural and forestry pests.

Monitor lizards are large, slender lizards up to 3.5 m long, featuring a very long, flexible tail and well-developed legs. They run swiftly, holding their bodies high above the ground. They are distributed in Africa, South Asia, and Australia. In Turkmenistan and Uzbekistan, the desert monitor can be found, reaching up to 60 cm in length with a yellowish-gray coloration and brown transverse stripes. It inhabits sandy deserts, feeding on Arthropods, rodents, and the eggs of turtles and birds. The largest specimen, measuring up to 365 cm, was discovered in 1914. It lives on the islands of Komodo and Flores (Indonesia), feeding on small mammals and birds, and frequently consuming wild boars killed by hunters.

The flying dragon is notable for its adaptation to gliding flight. It is distributed in the forests of South Asia. Jumping from tree to tree, it can cover distances of up to 20 m.

Iguanas are large lizards up to 1.5 m long, distributed almost exclusively in the Western Hemisphere. They inhabit mountains, forests, and deserts, while some species live in Water—occasionally even in the sea. They reproduce by laying eggs and ovoviviparity. The local population uses iguana eggs and meat for food.

Suborder Chameleons (Chamaeleontes). Chameleons are reptiles closely related to lizards but highly specialized, adapted primarily to an arboreal lifestyle. Most have a body length of 25–35 cm, the largest reach up to 50 cm (rarely 60 cm), and the smallest do not exceed 5 cm. The chameleon's trunk is laterally compressed, with a sharp dorsal keel. The legs are long and adapted for climbing. The toes are fused into two opposing groups resembling pincers, which can tightly grip tree branches. The tail is long and prehensile, used during climbing. Their visual Organs are unique: the eyelids are thick, convex, covered with small scales, and feature a small aperture for the pupil. The Movements of the left and right eyes can occur asynchronously, which is crucial when catching insects as it widens the field of view. A chameleon's body can inflate significantly due to air filling its pulmonary sacs. The Variability of chameleons' coloration is well known, driven by the shifting of Skin pigments under METABOLISM/18.html">The Influence of various environmental factors (e.g., light, Temperature, fear). Chameleons are distributed in Madagascar, Africa, Asia Minor, India, and southern Spain. Most live in forests, spending a great deal of time in trees hunting insects. When hunting, a chameleon rapidly projects its long Tongue, the thickened tip of which resembles a cylinder hollowed out at the front. Chameleons typically sit motionless on the branches of trees and shrubs for hours, watching for flying and crawling insects. While the body remains completely still, their eyes move constantly. Occasionally, chameleons will slowly stalk their prey.

Suborder Snakes (Serpentes). There are approximately 2,300 to 2,500 species of snakes. They are distributed globally, though they numerically predominate in warm latitudes, inhabiting forests, deserts, steppes, and mountains. Most species lead a terrestrial lifestyle, but some can live in trees, underground, or in water.

Snakes possess elongated bodies that show little external division into HEAD, neck, trunk, and tail. Paired limbs and their girdles are virtually absent. Movable eyelids and tympanic membranes are likewise missing.

The body is covered with horny scales and shields that are periodically renewed. Molting proceeds in a unique manner: the old surface layer of skin detaches at the jaws and gradually peels off the body inside out, much like a glove finger being pulled off. The surface layer of the fused eyelids also peels off during molting, which is why snakes' eyes appear most transparent immediately afterward.

The Structure of the skull features A number of adaptations that ensure the swallowing of large prey. The bones of both jaws and the palate are connected by elastic ligaments, allowing the Mouth to open extremely wide. Food is swallowed through alternating movements of the left and right halves of the lower jaw, effectively allowing the snake to "crawl over" its prey. The passage of a large food bolus through the anterior digestive tract is facilitated by the secretion of Salivary Glands. Most snakes are non-venomous; they kill their prey through the mechanical action of their teeth or their muscular body, which constricts around the victim. In venomous snakes, several anterior teeth are enlarged and contain canals or grooves through which venom flows.

Due to their elongated body shape and undulating locomotion, THE Vertebral Column consists of A large number (140–435) of uniform vertebrae. Only the right lung is developed, while the left lung is rudimentary if present at all. The Kidneys are greatly elongated, and the Urinary Bladder is absent. Reproduction occurs via oviparous, ovoviviparous, and viviparous Methods.

Snakes feed on animal prey of varying sizes—ranging from small insects and rodents to deer fawns. They lie in wait for their prey and strike with lightning speed. Venomous snakes attack humans only when disturbed.

Boas range from small species, up to 1 m long, to large ones reaching up to 10 m. They possess vestigial hind limbs, and their coloration is typically mottled.

Almost all boas are distributed in the tropical Regions of the Eastern and Western Hemispheres. Only a few species are found in the steppes and deserts of Central Asia and the Caucasus. Boas inhabit brush thickets and swamps, and are typically active at night. In dense forests, where twilight persists even during the day, they also hunt during daylight hours. They crawl toward their prey slowly and cautiously, catching it with a short-range strike and suffocating it by coiling their bodies in multiple turns around the victim.

The most famous is the reticulated python, measuring 5–6 to 10 m in length, distributed in southern Asia and the Indo-Malayan Archipelago. The boa constrictor reaches 5–6 m and inhabits South America. In Central Asia and the Caucasus lives the smallest representative—the sand boa—measuring up to 1 m long. It leads a nocturnal lifestyle, spending the day in rodent burrows or buried in the sand, beneath the surface layer of which it moves freely. It hunts jerboas, gerbils, and small reptiles.

Colubrids are the most numerous group of snakes, numbering over 1,000 species. The venomous teeth of colubrids lack an internal canal, and venom flows along a groove on the anterior surface of the tooth.

The grass snake differs from other species by the presence of two yellow, symmetrically arranged spots behind its temples on an otherwise dark head. In our country, it is distributed throughout the European part, extending into Siberia as far as Transbaikalia along the banks of swamps, rivers, and ponds. It feeds on frogs, lizards, rodents, and occasionally insects; fish are consumed rarely. It reproduces by laying eggs, which it deposits in decaying plant litter in damp places.

Racers, which grow up to 2 m long, are closely related to grass snakes. They lack venomous teeth, but when cornered or pursued, they may rush at a person and bite. Racers are distributed in the southern Russian steppes, the Caucasus, Central Asia, and the Russian Far East.

The smooth snake is a small, non-venomous, reddish-brown snake up to 75 cm long. It is found in the central and southern Zones of the European part of Russia, typically in brushwood or forests, avoiding damp areas. It feeds primarily on lizards.

In the desert regions of Central Asia, the arrow snake is abundant. It has a slender body up to 1 m long, yellowish-gray with longitudinal rows of spots. When pursued, this snake flees rapidly and hides in the branches of shrubs, which it climbs deftly. It is venomous and kills its prey by constricting it with its body or by biting.

Elapids include venomous cobras. They have the ability to flatten their neck, an adaptation enabled by the mobility of their Cervical Ribs. Cobras assume a threatening posture when agitated. In southern Turkmenistan, the oxus cobra (or transcaspian cobra) can be found, inhabiting gorges and areas near human settlements; its bite is extremely dangerous. Sea snakes are closely related to elapids and live in the tropical waters of the Pacific and Indian Oceans. The tails of these snakes are broad and paddle-shaped. Most species are ovoviviparous, and all are venomous. Their venom is highly toxic, though injected in small doses.

Vipers are venomous snakes with the most highly developed venom apparatus. Their venomous fangs are pierced by internal canals. The upper jaws are short, and when the mouth opens, the fangs swing forward. The common viper is widespread across our country, spanning both the entire European part and Siberia. It typically lives in forests and avoids swamps. During the day, vipers are often seen basking on tree stumps, brushwood piles, etc. They hunt at night, catching mice, voles, birds, lizards, frogs, and insects. They reproduce via ovoviviparous development. For the winter, they gather in underground shelters, congregating in massive numbers. A viper's bite is particularly dangerous for frail or sick individuals and children.

In Central Asia and the Caucasus lives the highly venomous lelantine viper (Levantine viper), reaching up to 2 m in length. The saw-scaled viper and the pit viper, which are also very venomous, can be found within our country's territory.