The appearance of reptiles. Origin and evolution of modern reptiles. Reasons for the extinction of ancient reptiles

Origin of reptiles

Origin of reptiles- one of important issues in the theory of evolution, the process as a result of which the first animals belonging to the class Reptilia appeared.

Permian period

From the Upper Permian deposits North America, Western Europe, Russia and China know the remains of cotylosaurs ( Cotylosauria). In a number of characteristics they are still very close to stegocephals. Their skull was in the form of a solid bone box with openings only for the eyes, nostrils and parietal organ, the cervical spine was poorly formed (although there is a structure of the first two vertebrae characteristic of modern reptiles - atlanta And epistrophy), the sacrum had from 2 to 5 vertebrae; the cleithrum, a skin bone characteristic of fish, was preserved in the shoulder girdle; the limbs were short and widely spaced.

The further evolution of reptiles was determined by their variability due to the influence of various living conditions that they encountered during reproduction and settlement. Most groups became more mobile; their skeleton became lighter, but at the same time stronger. Reptiles consumed a more varied diet than amphibians. The technique of its extraction has changed. In this regard, the structure of the limbs, axial skeleton and skull underwent significant changes. For the majority, the limbs became longer, and the pelvis, gaining stability, was attached to two or more sacral vertebrae. The “fishy” bone, the cleithrum, has disappeared from the shoulder girdle. The solid shell of the skull has undergone partial reduction. In connection with the more differentiated muscles of the jaw apparatus, pits and bone bridges separating them appeared in the temporal region of the skull - arches that served for attachment complex system muscles.

Synapsids

The main ancestral group that gave rise to all the diversity of modern and fossil reptiles were cotylosaurs, but the further development of reptiles followed different paths.

Diapsids

The next group to separate from the cotylosaurs were the Diapsida. Their skull has two temporal cavities, located above and below the postorbital bone. Diapsids at the end of the Paleozoic (Permian) gave an extremely broad adaptive radiation systematic groups and species that are found both among extinct forms and among living reptiles. Among diapsids, two main groups emerged: Lepidosauromorpha and Archosauromorpha. The most primitive diapsids from the group of Lepidosaurs are the order Eosuchia ( Eosuchia) - were the ancestors of the Beak-headed order, from which only one genus is currently preserved - hatteria.

At the end of the Permian, squamate (Squamata) separated from the primitive diapsids, becoming numerous in the Cretaceous period. By the end Cretaceous period Snakes evolved from lizards.

Origin of archosaurs

see also

• Temporal arches

Notes

Literature

• Naumov N.P., Kartashev N.N. Part 2. Reptiles, birds, mammals // Zoology of vertebrates. - M.: graduate School, 1979. - P. 272.

Wikimedia Foundation. 2010.

Permian period

Remains of cotylosaurs (Cotylosauria) are known from the Upper Permian deposits of North America, Western Europe, Russia and China. In a number of characteristics they are still very close to stegocephals. Their skull was in the form of a solid bone box with openings only for the eyes, nostrils and parietal organ, the cervical spine was poorly formed (although there is a structure of the first two vertebrae characteristic of modern reptiles - atlanta And epistrophy), the sacrum had from 2 to 5 vertebrae; the cleithrum, a skin bone characteristic of fish, was preserved in the shoulder girdle; the limbs were short and widely spaced.

The further evolution of reptiles was determined by their variability due to the influence of various living conditions that they encountered during reproduction and settlement. Most groups became more mobile; their skeleton became lighter, but at the same time stronger. Reptiles consumed a more varied diet than amphibians. The technique of its extraction has changed. In this regard, the structure of the limbs, axial skeleton and skull underwent significant changes. For the majority, the limbs became longer, and the pelvis, gaining stability, was attached to two or more sacral vertebrae. The “fish” bone, the cleithrum, has disappeared from the shoulder girdle. The solid shell of the skull has undergone partial reduction. In connection with the more differentiated muscles of the jaw apparatus, pits and bone bridges separating them appeared in the temporal region of the skull - arches that served to attach a complex system of muscles.

Synapsids

The main ancestral group that gave rise to all the diversity of modern and fossil reptiles was probably cotylosaurs, but the further development of reptiles followed different paths.

Diapsids

The next group to separate from the cotylosaurs were the Diapsida. Their skull has two temporal cavities, located above and below the postorbital bone. Diapsids at the end of the Paleozoic (Permian) gave an extremely broad adaptive radiation to systematic groups and species, which are found both among extinct forms and among living reptiles. Among diapsids, two main groups have emerged: lepidosauromorphs (Lepidosauromorpha) and archosauromorphs (Archosauromorpha). The most primitive diapsids from the group of lepidosaurs - the order Eosuchia - were the ancestors of the order Beaked, from which only one genus is currently preserved - hatteria.

At the end of the Permian, squamate (Squamata) separated from primitive diapsids, becoming numerous in

Late Devonian. These were armored-headed amphibians (the outdated name is stegocephals; now most of these animals are included in the labyrinthodonts). They lived near bodies of water and were closely associated with them, since they reproduced only in water. The development of spaces remote from bodies of water required a significant restructuring of the organization: adaptation to protecting the body from desiccation, breathing atmospheric oxygen, efficient movement on solid substrate, and the ability to reproduce outside of water. These are the main prerequisites for the emergence of a qualitatively different new group of animals - reptiles. These changes were quite complex; for example, it required the development of powerful lungs and a change in the nature of the skin.

From the point of view of a progressive method of classification - cladistics, which considers the position of organisms from the point of view of their origin, and not the characteristics of their organization (in particular, the classic “reptilian” characteristics of crocodiles, such as cold-bloodedness and limbs located on the sides of the body, are secondary), reptiles are all developed amniotes, excluding taxa included in the clade synapsids and possibly anapsids.

Carboniferous period

The remains of the most ancient reptiles are known from the Upper Carboniferous (about 300 million years ago). It is assumed that the separation from amphibian ancestors should have begun, apparently, in the Middle Carboniferous (320 million years), when from anthracosaurs like Diplovertebron, forms became isolated, apparently better adapted to the terrestrial way of life. From such forms a new branch arises - the Seymouriomorpha, the remains of which were found in the Upper Carboniferous - Middle Permian. Some paleontologists classify these animals as amphibians.

Permian period

Remains of cotylosaurs (Cotylosauria) are known from the Upper Permian deposits of North America, Western Europe, Russia and China. In a number of characteristics they are still very close to stegocephals. Their skull was in the form of a solid bone box with openings only for the eyes, nostrils and parietal organ, the cervical spine was poorly formed (although there is a structure of the first two vertebrae characteristic of modern reptiles - atlanta And epistrophy), the sacrum had from 2 to 5 vertebrae; the cleithrum, a skin bone characteristic of fish, was preserved in the shoulder girdle; the limbs were short and widely spaced.

The further evolution of reptiles was determined by their variability due to the influence of various living conditions that they encountered during reproduction and settlement. Most groups became more mobile; their skeleton became lighter, but at the same time stronger. Reptiles consumed a more varied diet than amphibians. The technique of its extraction has changed. In this regard, the structure of the limbs, axial skeleton and skull underwent significant changes. For the majority, the limbs became longer, and the pelvis, gaining stability, was attached to two or more sacral vertebrae. The “fish” bone, the cleithrum, has disappeared from the shoulder girdle. The solid shell of the skull has undergone partial reduction. In connection with the more differentiated muscles of the jaw apparatus, pits and bone bridges separating them appeared in the temporal region of the skull - arches that served to attach a complex system of muscles.

Synapsids

The main ancestral group that gave rise to all the diversity of modern and fossil reptiles was probably cotylosaurs, but the further development of reptiles followed different paths.

Diapsids

The next group to separate from the cotylosaurs were the Diapsida. Their skull has two temporal cavities, located above and below the postorbital bone. Diapsids at the end of the Paleozoic (Permian) gave an extremely broad adaptive radiation to systematic groups and species, which are found both among extinct forms and among living reptiles. Among diapsids, two main groups have emerged: lepidosauromorphs (Lepidosauromorpha) and archosauromorphs (Archosauromorpha). The most primitive diapsids from the group of lepidosaurs - the order Eosuchia - were the ancestors of the order Beaked, from which only one genus is currently preserved - hatteria.

At the end of the Permian, squamate (Squamata) separated from the primitive diapsids, becoming numerous in the Cretaceous period. By the end of the Cretaceous period, snakes evolved from lizards.

Origin of archosaurs

see also

• Temporal arches

Notes

Literature

• Naumov N. P., Kartashev N. N. Part 2. Reptiles, birds, mammals// Zoology of vertebrates. - M.: Higher School, 1979. - P. 272.

A transitional form is an organism with an intermediate state that necessarily exists during a gradual transition from one biological type of structure to another. Transitional forms are characterized by the presence of more ancient and primitive (in the sense of primary) traits than their later relatives, but, at the same time, the presence of more progressive (in the sense of later) traits than their ancestors. As a rule, when speaking about intermediate forms, they mean fossil species, although intermediate species do not necessarily have to die out. Many transitional forms are known, illustrating the origin of tetrapods from fish, reptiles from amphibians, birds from dinosaurs, mammals from theriodonts, cetaceans from terrestrial mammals, horses from a five-toed ancestor and humans from ancient hominids.

Reptiles, or reptiles (Latin: Reptilia), are a class of predominantly terrestrial vertebrates, including modern turtles, crocodiles, beaked animals and squamates. Cladists are classified as reptiles and birds, since otherwise the former would be a paraphyletic group.

In the 18th-19th centuries, reptiles, cold-blooded terrestrial vertebrates, were grouped together with amphibians. Traditionally, this group included various vertebrates, which, according to initial ideas, were similar in their organization to modern reptiles(for example, some synapsids - the ancestors of modern mammals). However, at present, questions about the physiology of many extinct groups of organisms remain open, and data on their genetic and evolutionary relationships do not support this kind of classification.

Many authors who adhere to traditional taxonomy believe that archosaurs (crocodiles, pterosaurs, dinosaurs, etc.) should be removed from the class of reptiles and combined into one class with birds, since birds are actually a specialized group of dinosaurs. About 10,885 species of non-avian reptiles are known in the world; 77 species live in Russia.

The largest land animals belonged to dinosaurs - representatives of ancient reptiles, currently represented only by birds. Reptiles flourished during the Mesozoic era, when they dominated the land, sea and air. At the end of the Cretaceous period, most reptiles became extinct. Modern non-avian reptiles are only scattered remnants of that world. However, ancient reptiles gave rise to the currently thriving group of animals - birds, and many of the adaptations that determined the evolutionary success of this group appeared in its archosaur ancestors, which were a specialized group of diapsids (warm-blooded, heat-insulating body cover - feathers, a developed brain, and etc).

Origin of reptiles

Origin of reptiles- one of the important issues in the theory of evolution, the process as a result of which the first animals belonging to the class Reptilia appeared.

Permian period

From the Upper Permian deposits of North America, Western Europe, Russia and China, remains of cotylosaurs are known ( Cotylosauria). In a number of characteristics they are still very close to stegocephals. Their skull was in the form of a solid bone box with openings only for the eyes, nostrils and parietal organ, the cervical spine was poorly formed (although there is a structure of the first two vertebrae characteristic of modern reptiles - atlanta And epistrophy), the sacrum had from 2 to 5 vertebrae; the cleithrum, a skin bone characteristic of fish, was preserved in the shoulder girdle; the limbs were short and widely spaced.

The further evolution of reptiles was determined by their variability due to the influence of various living conditions that they encountered during reproduction and settlement. Most groups became more mobile; their skeleton became lighter, but at the same time stronger. Reptiles consumed a more varied diet than amphibians. The technique of its extraction has changed. In this regard, the structure of the limbs, axial skeleton and skull underwent significant changes. For the majority, the limbs became longer, and the pelvis, gaining stability, was attached to two or more sacral vertebrae. The “fish” bone, the cleithrum, has disappeared from the shoulder girdle. The solid shell of the skull has undergone partial reduction. In connection with the more differentiated muscles of the jaw apparatus, pits and bone bridges separating them appeared in the temporal region of the skull - arches that served to attach a complex system of muscles.

Synapsids

The main ancestral group that gave rise to all the diversity of modern and fossil reptiles were cotylosaurs, but the further development of reptiles followed different paths.

Diapsids

The next group to separate from the cotylosaurs were the Diapsida. Their skull has two temporal cavities, located above and below the postorbital bone. Diapsids at the end of the Paleozoic (Permian) gave an extremely broad adaptive radiation to systematic groups and species, which are found both among extinct forms and among living reptiles. Among diapsids, two main groups emerged: Lepidosauromorpha and Archosauromorpha. The most primitive diapsids from the group of Lepidosaurs are the order Eosuchia ( Eosuchia) - were the ancestors of the Beak-headed order, from which only one genus is currently preserved - hatteria.

At the end of the Permian, squamate (Squamata) separated from the primitive diapsids, becoming numerous in the Cretaceous period. By the end of the Cretaceous period, snakes evolved from lizards.

Origin of archosaurs

see also

• Temporal arches

Notes

Literature

• Naumov N.P., Kartashev N.N. Part 2. Reptiles, birds, mammals // Zoology of vertebrates. - M.: Higher School, 1979. - P. 272.

Wikimedia Foundation. 2010.

Dinosaurs, brontosaurs, ichthyanosaurs, pterosaurs - these and many other of their relatives are known modern people thanks to archaeological excavations. IN different time V different regions individual fragments of the skeletons of ancient reptiles were found, from which scientists scrupulously reconstructed the appearance and lifestyle of archaic animals. Today, the remains of reptiles can be admired in many museums around the world.

General characteristics of ancient reptiles

Archaic reptiles are the second stage in the ontogenesis of the animal world after amphibians. Ancient reptiles are pioneers among vertebrates that are adapted to life on land.

A common feature of ancient reptiles is the skin of the body, covered dense layer horny formations. Such “protection” made it possible for animals not to be afraid of the scorching rays of the sun and to freely settle over the entire surface of the Earth.

The apogee of the development of ancient reptiles occurs in the Mesozoic era. Archaic dinosaurs are the largest vertebrates living on our planet. Over time, they adapted to fly and swim underwater. In a word, animals reigned supreme in all earthly elements.

The history of ancient reptiles

The cause of the emergence of archaic lizards was a change in climatic conditions. Due to the cooling and drying out of many reservoirs, amphibians were forced to move out of their usual aquatic habitat onto land. As a result of evolution, ancient reptiles appeared as a more advanced link of lower vertebrates.

Climate change has caused major mountain-building processes. Ancient amphibians had thin skin without protective covering, underdeveloped internal organs, imperfect lungs. The creatures reproduced primarily by spawning. This method of procreation could not be carried out on land due to the fragility of the future offspring. The lizards laid eggs that had a hard shell and could withstand changing climatic conditions.

The ability to adapt to any environment has led to the emergence various types ancient reptiles. The most famous of them:

• terrestrial animals (dinosaurs, theriodont lizards, tyrannosaurs, brontosaurs);
• swimming fish lizards (ichthyosaurs and plesiosaurs);
• flying (pterosaurs).

Types of ancient lizards

Depending on their habitat and method of feeding, archaic reptiles are divided into the following types:

• Flying dinosaurs - pterodactyls, rhamphorhynchus, etc. The largest gliding lizard was the pteranodon, whose wingspan reached 16 meters. The rather fragile body deftly moved through the air even in weak winds thanks to a natural rudder - a bone ridge on the back of the head.
• Aquatic reptiles - ichthyosaur, mesosaur, plesiosaur. The food of lizard fish included cephalopods, fish and other sea ​​creatures. The body length of aquatic reptiles ranged from 2 to 12 meters.

• Herbivorous chordates.
• Carnivorous dinosaurs.
• Animal-toothed lizards are reptiles whose teeth were not the same, but were divided into fangs, incisors, and molars. The most famous theriodonts are pterosaurs, dinosaurs, etc.

Herbivores

Many ancient reptiles were herbivores - sauropods. Climatic conditions contributed to the development of plants suitable for food by lizards.

The lizards that ate grass included:

• Brontosaurus.
• Diplodocus.
• Iguanodon.
• Stegosaurus
• Apatosaurus and others.

The teeth of the found remains of reptiles were not developed enough to eat carnal food. The structure of the skeleton indicates the adaptation of archaic animals to pluck leaves located on the crown tall trees: almost all herbivorous dinosaurs had long neck and a rather small head. The body of “vegetarians,” on the contrary, was huge and sometimes reached 24 meters in length (for example, a brachiosaurus). Herbivores moved exclusively on four strong legs, and for reliability they also relied on a powerful tail.

Lizard predators

The most ancient reptile predators, unlike their herbivorous relatives, were relatively small in size. Most major representative archaic carnivores - tyrannosaurus, whose body reached 10 meters in length. Predators had strong, large teeth and a rather terrifying appearance. Reptile carnivores include:

• Tyrannosaurus
• Ornithosuchus.
• Euparkeria.
• Ichthyosaur.

Reasons for the extinction of ancient reptiles

Having adapted to the conditions of the Mesozoic, dinosaurs inhabited almost all habitats. Over time, the climate on Earth began to become harsher. The gradual cooling did not contribute to the comfort of heat-loving animals. As a result, the Mesozoic era became a period of prosperity and disappearance of archaic dinosaurs.

Another reason for the extinction of ancient reptiles is considered to be the spread large quantity plants that are not suitable for dinosaur food. Poisonous grass destroyed many species of lizards, most of which were herbivores.

Didn't contribute further development ancient vertebrates and the natural struggle for survival. The place of reptiles began to be taken by stronger animals - mammals and birds, warm-blooded and with higher brain development.