Turtles are reptiles, which are distinguished from other vertebrates by features of the skeleton structure. It is believed that these unique animals lived even 220 million years ago, which makes them one of the oldest reptiles older than lizards, snakes or crocodiles. Modern science knows 327 species of turtles, and many of them are endangered.
Skeleton of a turtle: features of the structure
The turtle skeleton has distinctive features in comparison with any other vertebrates, in which the blades are located outside the chest, as in humans, large cats, elephants, goats and monkeys. The tortoiseshell skeleton is part of the bone structure. This means that the protective shell is more than just an external coating. It is an integral part of the body of the animal. When the skeleton of turtles begins to form, the scapulae and the ribs become part of the growing shell. The skeleton consists of bones and cartilage.
As a rule, it is divided into 3 main parts:
- skull (cranium, jaws and hyoid apparatus),
- axial skeleton of a tortoise, internal or external (shell, vertebrae, ribs and derived ribs),
- appendicular skeleton (limbs, chest and pelvic structures).
The uniqueness of the structure of sea turtles
The anatomy of a sea turtle is unique in that it is one of the few creatures that have both an internal and external skeleton. In all species, with the exception of leathery ones, the external frame provides protection and support for the internal organs. It consists of a bone shell, which, in turn, is divided into two halves: the lower and upper armor plastron. The muscles are attached to the inner skeleton. Like the land, the spine of sea turtles grows together with the shell.
Long fingers in the limbs form flippers that are used to move in the water. They are also used by females to dig holes for eggs during the nesting period. Sea turtles have no teeth in their mouths. Instead, there is a sharp beak, with which you can crush food. The leathery mouth contains a number of undeveloped thorns.
Ancestors of turtles: what were they?
Despite the large number of fossil turtles found, scientists still cannot say with absolute accuracy who was the ancestor of these animals. Disputes on this issue are ongoing in the scientific community so far. But one thing scientists can say quite definitely: the first tortoise appeared in the Mesozoic era. This animal had only one half of its shell and a mouth full of sharp teeth. Ten million years later, the tortoise was completely formed shell, but the teeth remained still at this time.
It is known that the fossil ancestors of turtles were incredibly large. They reached a length of more than two and a half meters and had a huge tail. In some specimens it reached the same length as the shell. At the end of the tail were large needle-shaped growths, and on the skull grew long curved horns.
At the moment, zoologists know about twenty-six species of turtles, twelve of them exist today.
Turtle skeleton: structure, photo and brief description
Turtles are a rare species of reptiles, which have a certain feature - part of the skeleton is turned out and turned out, so some muscles and organs work differently than other reptiles.
The shell of the animal is part of its skeleton, so the turtles can not leave their "house" and exist outside it. It consists of two plates:
- top - carapax,
- bottom - plastron.
The upper part is spliced with the spine and ribs, and the lower - with the clavicles and ribs. The structural features of the skeleton have led to the fact that most of the abdominal muscles of the turtles are atrophied or very poorly developed, but the neck muscles and muscles of the legs are able to withstand a very serious load. In some species of turtles there is an opportunity in case of danger to pull the plastron tightly to the carapax. In this situation, the animal is in absolute safety, which allowed the species to survive in a changing external environment.
The skeleton of turtles usually has three divisions:
- axial skeleton
- appendicular skeleton.
All departments are composed of bones and cartilage, including armor plates.
Turtle skeleton: the structure of the skull
The main feature of the skeleton of turtles is the fact that the skull is located on a long and mobile neck. Due to this, the head can be completely drawn into the shell or be located sideways in it.
The divisions of the skeleton of the skull are twenty bones, the orbits are large and separated by a septum. The largest are the frontal and parietal bones, in the upper part of the skull there is a special auricle. It is pressed into the back of the skull.
The animal has an upper and lower jaw, there are no teeth in turtles. Instead, in the mouth is a similarity to the beak, which is a horny dense plate. They help the animal to bite off food and pull it to itself. The fat tongue, which many predatory turtles, like a worm, lure the victim to, helps in this process.
Turtles: what you did not know about them
Turtles are amazing creatures. We do not know much about these creatures, and after all they can give us a lot of surprises. For example, a tortoise shell contains phosphorus. Therefore, if the animal has been basking in the sun for a long time, it will glow at night.
All turtles memorize human faces perfectly and react to a tender voice by pulling the head out of their shell. Rough intonations in conversation, in turn, provoke the animal to hide in its "house".
Large sea turtles are not afraid of encounters with sharks, predators are not able to swallow an animal. Some species of turtles can live without food for about five years. The record holder in abstinence is the marsh turtle.
Members of the detachment live in the steppes, foothills of Pakistan and India, in the deserts of Turkmenistan, Syria and Libya. As with other animals belonging to the family of reptiles, in the structure of their body, as well as in the processes of vital activity, one can find a number of idioadaptations to the dry and hot climate. Among such devices emit a dense leathery integument, the absence of mucous glands, the presence of horny scales and scutes. These formations are composed of fibrillar proteins - keratins. Their function is to increase the mechanical strength of the outer covers.
Since land turtles, for example, steppe, Central Asian, feed on rather rigid vegetable food, they have a beak on their head, a peculiar process with sharp edges with teeth. They turtles tear off parts of plants and fray them lumpy protrusions. There are also eyes on the head. They are limited to three centuries: lower, upper and third. Presented in the form of a leathery film, covering the eye only half. All turtles have well developed binocular vision and are well oriented in the environment.
To answer the question of whether the turtle has a skeleton, recall that the body of a reptile is divided anatomically into 4 parts. It consists of the head, neck, torso and tail. Consider the structure of the turtle in the cut. So, her spine consists of 5 sections: cervical, thoracic, lumbar, sacral and caudal. The skeleton of the head is completely bony. It is connected to the neck with two movable vertebrae. In total, the turtle has 8 cervical vertebrae. The head at the time of danger is drawn into the shell, due to the presence of holes in it. Land reptiles perceive sounds of low frequency. Turtles are referred to as "silent" animals, as their vocal cords are anatomically poorly developed. Therefore, they emit a hiss or squeak.
The structure and functions of the Karapaks
Continuing to study the skeleton of a turtle, consider the upper part of its shell. It has a bulge that looks like a small bell. In land turtles, it is especially tall and massive, in aquatic turtles it is flatter, streamlined. Carapax consists of two layers. The outer contains keratin scales - shields, and the bottom has a bone structure. Attached to it are the arches of the vertebrae of the lumbar-thoracic and rib. Coloring and drawing of the horny shields of karapaks are used by taxonomy to determine the species of animals. It is because of the tortoise shell that have been and remain the object of fishing. A frame for glasses, cases, and handles of knives are made from it. The shell has several holes in which the animal pulls in the head, limbs and tail at the moment of danger.
Plastron and its value
The lower part of the shell is called plastron. Between him and karapaksom is the soft body of the animal. Both halves are united by bone shell. Plastron itself is an anatomical derivative of the belt of the forelimbs and ribs. It is as if “soldered” into the body of a turtle. Ground forms have a massive plastron. And in marine life, it is reduced to cruciform plates located on the abdominal part of the body. On the plates of the shell, concentric lines are formed due to growth. According to them, herpetologists can determine the age of the tortoise and its state of health.
Characteristics of the skeleton of the belts of the front and hind legs of a turtle
The skeleton of a tortoise, which is shown below, indicates that animals of this species belong to reptiles. They have attached the bones of the forelimb girdle to the spine: scapula, collarbone and crow formation. They are located in the middle of the chest. The scapula is connected to the carapace of the muscular fold at the location of the first vertebra. The hind limb girdle consists of pubic, iliac, and ischial bones. They form the pelvis. The tail section consists of many small vertebrae, so it is very mobile.
Features of the structure of limbs of land turtles
The forelimbs of reptiles consist of the shoulder, forearm, wrist, metacarpus, and phalanges of the fingers, which is similar to the skeleton of other classes of terrestrial vertebrates. However, there are differences in the structure of the bones of the forelimb. For example, the tubular bone of the shoulder is short, and their number, forming the wrist, is smaller than in mammals. The hind limbs also have anatomical features. The femur is very short, and their number in the foot is also reduced. This is especially noticeable in land turtles: box-shaped, red-eared, steppe. As they move along the surface of the earth, the bones of the phalanges of their fingers experience constant mechanical loads. Thus, the turtle's skeleton has the necessary idioadaptation, contributing to its adaptation to the habitat.
Pontoon: structure and characteristics of life
Among all other species, this animal is most popular as a domestic inhabitant. The structure of the tortoise red-eared typical of freshwater forms. Her head is well mobile, the neck is long, the shell is represented by green carapace, and the plastron is yellow. Because of this, the turtle is often called yellow-bellied. The limbs are massive, covered with horny shields, ending in claws. In nature, they feed on insects, larvae and fry of fish, as well as algae, living in abundance along river banks. It is easy to distinguish the female from the male: it is more massive and longer, and its mandibles are larger. These animals breed from the end of February to May, laying from 4 to 10 eggs in the sand pits. Small turtles hatch usually in July or August.
Land Turtle Species
This group of reptiles is represented by such animals as the Central Asian tortoise listed in the Red Book, the Balkan, the Panther. There are only about 40 species. The outer skeleton of a turtle is a shell. It is very massive, with a highly raised plastron. The animals themselves are quite inactive. The Central Asian tortoise is little dependent on water sources. It can do for a long time without it, feeding on succulent leaves or sprouts of grassy plants. Since the animal has to adapt to the dry climate of steppe or semi-desert, its annual activity is strictly regulated. It is only 2-3 months old, and the rest of the year the tortoise spends half-stupor or hibernates in holes dug in the sand. This happens twice a year - in summer and in winter.
The structure of the land turtle is characterized by a number of adaptations associated with life on land. These are columnar massive limbs, the phalanges of the fingers completely fused, leaving short claws free. The body is covered with horny scales that prevent excessive evaporation and ensure the preservation of water in the tissues of the animal. Thus, animals are reliably protected by ultrastrong bone-horn shell. In addition, they can scare off potential enemies with harsh hissing sounds or a very fast emptying of a voluminous bladder. All species of land turtles are long-lived. They can live from 50 to 180 years. In addition, they are highly adaptable and resilient.
Nevertheless, let's not forget that 228 species of turtles are in need of protection and are on the verge of extinction. For example, the area of the green turtle is rapidly decreasing. It serves as an object of fishing, as a person eats its meat. In connection with the urbanization and reduction of the area of natural habitat, the number of animals is annually decreasing. The question of the expediency of keeping turtles in human dwellings remains controversial, even if they are localized in specially equipped conditions of the terrarium. An insignificant number of these animals live in captivity to their biological age. The majority perishes from the ignorant and irresponsible attitude towards them of a person.