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Archeopteryx flew poorly, they probably could only plan with the help of wings.

Archeopteryx flew poorly, they probably could only plan with the help of wings.

Superclass bigos (AGNATHA). Bigos include the most primitive vertebrates with a cartilaginous skeleton that lead an aquatic lifestyle and fish that resemble them. Their distinguishing feature from all other vertebrates is the lack of jaws. Nowadays, roundworms (lampreys) live in the seas, they are unknown in the fossil state.

Ancient extinct bigos are very diverse in shape and size. Remains of shells covering the head and front of the torso have been preserved in the fossil state. This shell consisted of fused bone plates and had the appearance of a shield, so bigos are often called corymbose. They were common in the Ordovician, Silurian and Devonian (especially in the late Silurian and early Devonian), lived in freshwater and salt basins. Representatives: genus Telodus (Thelodus) from the Ordovician; genus Cephalaspis (Cephalaspis) from the Early Devonian.

Superclass of fish (PISCES). Fish are aquatic vertebrates that retain gills throughout their lives. Their limbs are represented by even and odd fins, the inner skeleton is cartilaginous or bony, the body is covered with scales of different structure. Fish appeared at the end of the Silurian, and in the Devonian they quickly conquered large sea and freshwater basins, ousting bigos. Therefore, the Devonian period is often called the “century of fish.”

The superclass of fish combines four classes, all of which were known in the Devonian period. This is a class of plate-skinned, a class of cartilaginous fish, a class of bony fish.

Bone fish are the most progressive group of fish. Bone fishes are divided into three subclasses: kisteperi, two-breathing, lucheperi.

Kisteperi fish are predators up to 3 m long. The anterior paired fins, which had a fleshy base from which leathery rays deviated (hence the name of the group), kisteperi fish could rest on the bottom. From these fins developed the forelimbs of the first terrestrial vertebrates – stegocephali, relative to the amphibian. Appearing in the early Devonian, kisteperi were the most numerous fish in the Middle and Late Devonian.

Representative: genus Holoptychius (Holoptychius) from the Devonian. To this day, the only genus Latimeria (Latimeria), discovered in 1938 off the southeast coast of Africa. This ancient fish is a living fossil. Currently, only a few specimens of latimeria have been caught.

Two-breathing fish combine gill respiration with pulmonary. They appeared in the Devonian, and still live only 6 species in South Africa, Australia and South America in freshwater in seasonal droughts. Dental plates, fragments of the skull and individual scales have been preserved in the fossil state. Finds of dicotyledons are important for paleogeography, they indicate an arid and hot climate. Distribution: Devonian – now. Representative: genus Dipterus (Dipterus) from the Middle Devonian.

Lucheperi is a thriving group of fish. These include modern and fossil marine and freshwater fish that have fins on long cartilaginous or bony rays (hence their name). Lucheperi appeared in the early Devonian, began to dominate from the Cretaceous period and are widespread today. Representative: genus Palaeoniscurn (Palaeoniscurn) from the late Permian.

Superclass four-legged (TETRAPODA). Four-legged – vertebrates that live mainly on land. They appeared in the late Devonian and descended from kisteperi fish. The transition to a terrestrial way of life led to the restructuring of the whole organism.

The paired front and hind limbs of terrestrial quadrupeds emerged from the paired fins of the crested feathers, the gills were replaced by the lungs, and the hearing aid developed. Quadrupeds are at a much higher stage of development than fish. These include four classes: amphibians, reptiles, birds and mammals.

Class amphibians (Amphibia)

Amphibians, or amphibians, are primitive and the most ancient terrestrial four-legged animals. In their structure still preserved some features of ancestors who lived in the water, although more features inherent in terrestrial vertebrates. In the course of their life cycle, they first go through the stage of larvae that develop in the water, breathe with their gills and are deprived of limbs, and then turn into adult four-legged forms that live out of the water.

All amphibians are cold-blooded animals, their body temperature depends on the environment. The lungs are poorly developed, the thin mucous skin is an additional respiratory organ. Most amphibians reproduce, like fish, by laying eggs in the water. Their skeleton is largely cartilaginous.

Modern amphibians are less widespread than other vertebrates, they mostly live in southern latitudes. Among them are tailless (frogs), tailed (salamanders, newts) and legless.

The first amphibians, the stegocephali, appeared in the late Devonian and lived until the beginning of the Jurassic. Stegocephali had a solid skull (hence their name) with holes for the eyes, nostrils and parietal eye. Their teeth were like those of crested feathers. Due to the imperfect structure of the limb belts, their movement on land was slow and awkward. Stegocephali resembled crocodiles, lived in swampy forests, swamps and lagoons. The spread on land of more highly developed was one of the reasons for the extinction of stegocephalus. Representative: genus Ichthyostega (Ichtyostega) from the Late Devonian.

Class crawling (Reptilia). Reptiles, or reptiles, are true terrestrial vertebrates that are at a higher level of development than amphibians. These are cold-blooded animals with more circulatory system. They reproduce with eggs that contain large amounts of nutrients. The larval stage in development falls out, and young animals differ from adults only in the smaller sizes. In reptiles more blood circulation, pulmonary respiration are made.

Very different structure of the skull, teeth differ in shape. The skeleton of the reptile is divided into five sections, this provides greater mobility of the body.

The first reptiles appeared at the end of the Carboniferous, and at the end of the Paleozoic era they reached great diversity. They were especially widespread in the Mesozoic. During this era, reptiles achieved dominance by inhabiting land, air, and the aquatic environment. Therefore, the Mesozoic is often called the era of reptiles, by the end of this era, most of them die out.

Turtles, snakes, lizards, crocodiles, chameleons and gutters are known among modern reptiles. All these animals are only remnants of the rich class in the Mesozoic, most reptiles belong to extinct groups.

According to the peculiarities of the structure of the skeleton and skull, the way of life (terrestrial and marine) and the time of existence (fossil and modern), reptiles are divided into a number of ideas for personal narratives subclasses, of which the main ones are briefly described below.

Subclass of Cotylosauria. Cotylosaurs (boiler-headed lizards) are the most primitive reptiles, close in structure to the body and skull to stegocephali. Cotylosaurs were the first true terrestrial animals among vertebrates, they existed from the end of the Carboniferous to the end of the Triassic. Representative: the genus Pareiasaurus (Late Permian) is a clumsy short-legged animal.

Subclass beast-like lizards (Synapsida). This extinct group of reptiles originated from primitive cotylosaurs in the late Carboniferous and was widespread in the late Permian and Triassic. Among these lizards were many predators. Mesozoic beast-like lizards were the ancestors of mammals. This is evidenced by the presence of teeth for different purposes, as in mammals: incisors, canines, buccal teeth. Distribution: Late Carboniferous – Middle Jurassic. Representative: the genus Inostrancevia from late Permian – a terrible predator of its time.

Subclass of fish lizard (Ichthyopterygia). These are aquatic reptiles, similar in appearance to fish and dolphins. Most of them were marine predators that ate fish. Distribution: Middle Triassic – chalk. Representative: the genus Ichthyosaur (Ichtyosaurus) from the Early Jurassic.

Subclass scaly lizards (Lepidosauria). This subclass includes snakes, lizards and several extinct groups of reptiles, which are intermediate forms between primitive reptiles – cotylosaurs and more highly organized – archosaurs. Distribution: Late Carboniferous – now. Representative: the genus Mososaurus (Mososaurus) from the Late Cretaceous – a giant sea lizard.

Subclass Archosauria. This subclass includes numerous Mesozoic dinosaurs and flying lizards – pterosaurs, as well as surviving crocodiles.

Dinosaurs (scary lizards) dominated the land in the Mesozoic, they were extremely diverse in shape and size. Known small, no more than cats, and giants, up to 30-40 m in length, mobile and clumsy, walking on two and four legs, carnivorous and herbivorous, covered with scales and devoid of shell.

Among the dinosaurs were the largest of all known animals that ever inhabited our planet with a body length of up to 40 m, weighing more than 30 tons and with a very small brain size. Some of the largest of the dinosaurs, like modern hippos, have spent part of their lives in the water.

Dinosaurs appeared in the middle of the Triassic and became extinct by the end of the Cretaceous. Representatives: genus Diplodocus from the Late Jurassic – a giant dinosaur with a body length of up to 30 m and weighing up to 30 tons; genus Iguanodon (Jguanodon); genus Stegosaurus from the late Jurassic genus Triceratops (Triceratops) fromlate chalk.

Pterosaurs – flying lizards – were the only group of reptiles that lived in the air. Their forelimbs turned into long sharp membranous wings (like the wings of bats). Among the pterosaurs are toothed ramforinhy, which had a tail and narrow wings (from 0.4 to 1 m in scope), and wide-toothed toothless pterodactyls with a wingspan of up to 8 m. with the advent of birds that were more adapted to life in the air. Representatives: the genus Rhamphorhynchus from the Late Jurassic and the genus Pteranodon from the Late Cretaceous.

Class of birds (Aves)

Birds are currently the most numerous class of terrestrial vertebrates. They are descended from primitive Triassic reptiles – archosaurs – and in general develop much higher than reptiles.

In the fossil state of the bird are very rare, because their fragile hollow bones are quickly destroyed. The Late Jurassic Archeopteryx occupies a transitional position between reptiles and modern birds. Archeopteryx had wings and feathers, but their jaws were still with teeth, at the end of the wings – three fingers with claws, and a long tail consisted of a large number of vertebrae. Archeopteryx flew poorly, they probably could only plan with the help of wings.

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