Why are birds called the ancestors of humans? These amazing ancient birds. The world's largest flying bird and the smallest

Birds are man's feathered friends. Their role in nature is invaluable. Read about them and their protection in the article.

Birds: general characteristics

Birds are highly organized warm-blooded animals. There are nine thousand species of modern birds in nature. The characteristic features of the class are the following:

• Feathers.
• Hard beak made of cornea.
• No teeth.
• A pair of forelimbs are transformed into wings.
• The chest, pelvic girdle and second pair of limbs have a special structure.
• The heart consists of four chambers.
• There is an air bag.
• The bird incubates the eggs.

Birds, the general characteristics of which are presented above, are capable of flying thanks to the listed features. This distinguishes them from other classes of vertebrate animals.

Appearance on earth

The origin of birds is explained by several theories. According to one of them, birds live in trees. At first they jumped from branch to branch. Then they glided, then made short flights within the same tree, and finally learned to fly in open space.

Another theory suggests that the origin of birds is related to the ancestors of birds, which were reptiles with four legs. Evolving, the scales became feathers, which allowed reptiles to jump while flying a short distance. Later the animals learned to fly.

The origin of birds from reptiles

Based on this theory, we can say that the ancestors of birds were also crawling reptiles. At first their nests were on the ground. This attracted predators who constantly destroyed the nests along with the chicks. Taking care of their offspring, the reptiles settled in the thicket of tree branches. At the same time, a hard shell began to form on the eggs. Before this they were covered with film. Instead of scales, feathers appeared, which served as a source of heat for the eggs. The limbs became longer and covered with feathers.

The origin of birds from ancient reptiles is obvious, according to scientists. The ancestors of birds begin to take care of their offspring: they feed the chicks in the nest. To do this, solid food was crushed into small pieces and placed in the beaks of the babies. With the ability to fly, the primitive birds of ancient times could better defend themselves against the attacks of their enemies.

Ancestors - waterfowl

The origin of birds, according to another theory, is connected with their aquatic counterparts. This version owes its existence to the remains of ancient birds that were found in China. According to scientists, they were waterfowl and lived more than a hundred million years ago.

According to the theory, birds and dinosaurs lived together for sixty million years. Among the finds were feathers, muscles, membranes. Examining the remains, paleontologists came to the following conclusion: the ancestors of ancient birds swam. To get food from the water, they dived.

If you study the origin of birds, it is not difficult to find similarities between them and representatives of other classes. The plumage is the most noticeable feature appearance birds Other animals do not have feathers. This is the difference between birds and other animals. the following:

• The toes and tarsus of many birds are covered with corneal scales and scutes, like those of reptiles. This means that scales on the legs can replace feathers. It is characteristic that the rudiments of feathers in birds and reptiles are no different. Only birds then develop feathers, and reptiles develop scales.
• Investigating the origin of birds, whose similarities with reptiles are incredible, scientists have determined that the jaw apparatus is more noticeable. Only in birds it turned into a beak, but in reptiles it remained the same, like in turtles.
• Another sign of similarity between birds and reptiles is their skeletal structure. The skull and spine are articulated by only one tubercle located in the occipital region. Whereas in mammals and amphibians, two tubercles are involved in this process.
• The location of the pelvic girdle of birds and dinosaurs is the same. This can be seen from the skeleton of the fossil. This arrangement is associated with the load on the pelvic bones when walking, since only the hind limbs are involved in supporting the body.
• Birds and reptiles have a four-chambered heart. In some reptiles, the chamber septum is incomplete, and then arterial and venous blood mix. Such reptiles are called cold-blooded. Birds have a higher organization than reptiles; they are warm-blooded. This is achieved by eliminating the vessel that carries blood from the vein to the aorta. In birds it does not mix with the arterial one.
• Another similar feature is egg incubation. This is typical for pythons. They lay about fifteen eggs. The snakes curl up above them, forming a kind of canopy.
• Birds are most similar to reptile embryos, which in the first stage of their development resemble fish-like creatures with tails and gills. This makes the future chick similar to other vertebrates in the early stages of development.

Differences between birds and reptiles

When paleontologists study the origins of birds, they compare the facts and findings collected bit by bit and find out how birds are similar to reptiles.

What are their differences, read below:

• When the birds got their first wing, they began to fly.
• The body temperature of birds does not depend on external conditions; it is always constant and high, while reptiles fall asleep during cold weather.
• In birds, many bones are fused; they are distinguished by the presence of a tarsus.
• Birds have air sacs.
• Birds build nests, hatch eggs and feed chicks.

First Birds

Fossil remains of ancient birds have now been found. After careful study, scientists came to the conclusion that they all belong to the same species that lived one hundred and fifty million years ago. These are Archeopteryx, which means “ancient feathers.” Their difference from today's birds is so obvious that Archeopteryxes were separated into a separate subclass - lizard-tailed birds.

Ancient birds have been little studied. general characteristics comes down to determining the appearance and some features of the internal skeleton. The first bird was small in size, about the size of a modern magpie. Her forelimbs had wings, the ends of which ended in three long fingers with claws. The weight of the bones is large, so the ancient bird did not fly, but only crawled.

Habitat: coastal areas of sea lagoons with dense vegetation. The jaws had teeth, and the tail had vertebrae. No connections have been established between Archeopteryx and modern birds. The first birds were not the direct ancestors of our birds.

The importance and protection of birds

The origin of birds is of great importance in biogeocenoses. Birds are integral part biological chain and participate in the circulation of living matter. Herbivorous birds feed on fruits, seeds and green vegetation.

Different birds play different roles. Granivores - eat seeds and fruits, some species - store them, transporting them over long distances. On the way to the storage location, the seeds are lost. This is how plants spread. Some birds have the ability to pollinate them.

Great role in nature. They control the number of insect populations by eating them. If there were no birds, the destructive activity of insects would be irreparable.

Man, to the best of his ability, protects birds and helps them survive in harsh winters. People are hanging temporary nest boxes everywhere. Tits, flycatchers, and blue tits settle in them. Winter periods characterized by a lack of natural food for birds. Therefore, birds should be fed by filling the nesting box with small fruits, seeds, and bread crumbs. Some birds belong to commercial species: geese, ducks, hazel grouse, wood grouse, black grouse. Their value for humans is great. Woodcocks, waders, and snipe are of sporting interest.

From time immemorial: the body and legs of Archeopteryx were covered with long feathers, three and a half centimeters. It can be assumed that the bird did not swing its legs. Feathers were inherited from ancestors who lived in more ancient times and used all four wings when flying.

Today: when filling bird nesting areas with food, you need to make sure that no salt gets in there. It is white poison for birds.

All the features of birds that distinguish them from reptiles are primarily adaptive in nature for flight. Therefore, it is quite natural to believe that birds evolved from reptiles.

Birds originate from the most ancient reptiles, whose hind limbs were built in the same way as those of birds. Transitional forms - Archeopteryx and Archaeornis - in the form of fossil remains (imprints) were found in Upper Jurassic deposits. Along with the features characteristic of reptiles, they have the structural features of birds.

Adaptation of birds to their environment

Birds have adapted well to a variety of living conditions: to life in swamps, an aquatic lifestyle, in the air, forests and bushes, plains or rocks.

For some birds (swifts, swallows, etc.) the air is the main habitat, as they feed on various flying insects in the air. Birds that forage in the air are inhabitants of cliffs, rocks and woody vegetation. Swallows and swifts, for example, have secondarily adapted to build their nests in human structures, replacing the slopes of banks and rocks.

Those birds that use air both as a medium of movement and as a medium for obtaining food spend most days in flight. They have the most perfect aircraft.

Small and medium-sized birds (swifts, swallows, falcons) have an extremely elongated wing, pointed towards the apex. Their tail is often deeply cut or forked. These birds fly very fast and can make unexpected turns. In larger species of birds, the aircraft is adapted for soaring. For example, in marine forms (gulls, petrels) the wing is relatively long and narrow, while in land forms (birds of prey) it is wider and shorter.

Birds that use water as a habitat and for obtaining food also have corresponding adaptations. They went in two directions: adaptations of the wings and adaptations of the legs.

Some birds (petrels) have extremely long wings and spend whole days hovering over the water and grabbing the food they see. Such birds can swim on water. Other birds (penguins) use wings to move in water, which act like oars. The penguin's wing feathers have turned into scale-like structures, so these birds cannot fly at all.

Those aquatic birds that use their feet when swimming and diving have developed membranes between their toes during evolution. The exception is the water hen, which swims well and does not have webbed feet.

Similarities between birds and reptiles
It is easy to see the similarities between the classes of birds and reptiles. In both, the skin is almost devoid of glands, but is protected by horny scales in reptiles and feathers in birds. Note that in birds scales are developed on the non-feathered parts of the skin (tarsus). Bird feathers are also horny structures that develop from scales. Both classes are oviparous, and eggs are structured in a similar way: shell, yolk and white. The embryos of birds and reptiles are similar in appearance.

The ancestors of birds are ancient reptiles

In the search for immediate reptilian ancestors, small primitive reptiles were selected pseudosuchia, who lived approximately 200 million years ago (Triassic period). In search of food, some of these creatures adapted to climbing trees and jumping from branch to branch. During evolution, this method turned out to be promising and helped primitive birds avoid competition among related species and escape from predators. As the scales lengthened, they turned into feathers, which helped the ancient ancestors of birds acquire the ability to plan, and then to be active, i.e. flapping, flight, which most modern birds have.

The oldest bird

Protoavia (1984) was found in Post, Texas, USA, with an estimated age of 225,000,000 years.

The first birds appeared in the Mesozoic era

The development of the Earth is divided into five periods of time called eras. The first two eras, Archeozoic and Proterozoic, lasted 4 billion years, that is, almost 80% of all earth history. During the Archeozoic, the formation of the Earth occurred, water and oxygen appeared. About 3.5 billion years ago, the first tiny bacteria and algae appeared. During the Proterozoic era, about 700 years ago, the first animals appeared in the sea. These were primitive invertebrate creatures, such as worms and jellyfish. The Paleozoic era began 590 million years ago and lasted 342 million years. Then the Earth was covered with swamps. During the Paleozoic, large plants, fish and amphibians appeared. The Mesozoic era began 248 million years ago and lasted 183 million years. At this time, the Earth was inhabited by huge dinosaur lizards. The first mammals and birds also appeared. The Cenozoic era began 65 million years ago and continues to this day. At this time, the plants and animals that surround us today arose.

Descended from coelurosaurs

Living at the end of the Triassic and in the Jurassic period, small carnivorous dinosaurs from the group coelurosaurs were bipedal with long tails and small forelimbs of the grasping type. They did not need to climb trees and glide from branch to branch. The active flight of ancient birds could have arisen on the basis of the flapping movements of the forelimbs, which helped knock down flying insects, for which, by the way, predators had to jump high. Coelurosaurs survived the mass extinction of the dinosaurs at the end of the Mesozoic era.

The very first dinosaur birds
In the Mesozoic era, that is, 150 million years ago, the ancestors of birds constituted the main group of land animals in Argentina. They are called theropods (Argentavis magnificens), beast-footed lizards, and they already knew how to fly. Therapods moved on two legs, their front legs turned into short grasping limbs. It was no longer possible to rely on them, but it was convenient to fight with prey. The powerful jaws of theropods were densely lined with teeth and resembled a saw blade. In place of worn-down teeth, new ones grew, so even when they grew old, the lizards could still torment their prey with the same fervor. (Sharks also renew their teeth.) During the process of evolution, some theropods developed a horny beak. Analyzing the anatomical features of theropods, it is believed that birds originated from these animals.

Fossils found in Argentina in 1979 indicate that this huge vulture-like bird had a wingspan of more than 6 m, a height of 7.6 m, and a weight of 80 kg.

Beast-like predatory lizard ornitholestes, which had a body length of 2.5 m, gives an idea of ​​ancient birds.

their wingspan was 7.5 m; they lived in Europe, Africa, North and South America and were carnivores (eating fish and aquatic invertebrates).

Modern bird that lived 120 million years ago

After studying the fossilized remains of a small bird found in Liaoning province in northern China, scientists came to the conclusion that "Confuciusornis sanctus" - as the ancient bird was dubbed - lived 120 million years ago. Judging by the structure of the beak, Confuciusornis resembled modern birds: the teeth were no longer there, but a horny sheath had appeared.

The appearance of flapping flight

In the Jurassic period, birds acquired the ability to actively fly. Thanks to the swings of their forelimbs, they were able to overcome the effects of gravity and gained many advantages over their ground-based, climbing and gliding competitors. Flight allowed them to catch insects in the air, effectively avoid predators and choose the most favorable environmental conditions for life. Its development was accompanied by a shortening of the long tail, replacing it with a fan of long feathers, well suited for steering and braking. Most of the anatomical transformations necessary for active flight were completed by the end of the Early Cretaceous (about 100 million years ago), i.e. long before the extinction of the dinosaurs.

There can be no talk of a direct relationship between lizards and birds.

Found by American scientists from North Carolina State University. They compared the changes in theropod limbs with the evolution of the wings of chickens, ostriches and cormorants. In the process of evolution, both of them retained only three fingers from the original five. However, American biologists have found that birds lack both external fingers, that is, the first and fifth. The lizards have lost their fourth and fifth fingers.

long bird
Skeleton of the lizard "unenlagia comahuensis", " long bird", found in May 1996 in Argentina, fills the gap separating the ancient theropod reptiles and the first bird, Archeopteryx.

Differences between birds and reptiles

Oh more high development birds are evidenced by an enlarged brain (in particular, the large size of the cerebral hemispheres and cerebellum in birds), perfect respiratory and circulatory systems- double breathing and separation of arterial blood from venous blood, as well as constant body temperature. All these improvements in the organization of birds are absent in reptiles.

The oldest bird flew

The debate over whether Archeopteryx could fly has continued since 1861, when the first fossil was found, until now. The answer was found only recently. The creature's fossilized brain was placed in an X-ray machine, allowing thin "slices" of the object to be obtained. These slices were combined in a computer into a three-dimensional model. It turned out that in its anatomy the brain of Archeopteryx is much closer to the brain of modern flying birds than to the brain of dinosaurs, as paleontologists previously assumed. The analysis revealed, in particular, semicircular canals in the inner ear used for balance, and enlarged lobes of the brain responsible for vision - features that affect flight efficiency. The “flying” brain developed simultaneously with wings, and the ability to fly itself developed in the process of evolution much faster than scientists previously thought.

Bones served as conditioner

When hunting, ancient lizard-bird theropods regulated their body temperature to avoid overheating. The function of the air conditioner was performed by hollow bones.

Archeopteryx is the direct ancestor of modern birds

The remains of an extinct bird resembling a magpie that lived in the second half of the Jurassic period, i.e. 140 million years ago, were discovered in Europe. In layers earth's crust Scientists have discovered the fossilized bones of the skeleton of an unknown creature, and nearby the imprints of its feathers. The bird got a name archaeopteryx (Archaeopteryx litographica), What does "ancient bird" mean? This small bird had sharp teeth in cells, a long, lizard-like tail, and forelimbs with three fingers bearing hooked claws.

Archeopteryx resembled a reptile

The shape of the Archeopteryx skull with teeth in both jaws and a very long tail with 20 vertebrae resembled a reptile. In most features, Archeopteryx was more like a reptile than a bird, except for the real feathers on the forelimbs and tail.

How did Archeopteryx fly?
The entire body of this creature, except the head, was covered with feathers, and the forelimbs had all the basic features of bird wings with flight feathers. Only the wing fingers were longer than those of modern birds and had claws. The feet had four toes: the first toe faced back, the rest - forward, which helped to clasp the branches well with the fingers. Tail feathers were attached in pairs on each vertebra of the long tail, and not, as in modern birds, in a wide fan on the coccygeal bone. Features of Arechaeopteryx indicate that it was capable of flapping flight, but only over very short distances.

An animal the size of a crow

Rahonavis This crow-sized animal lived about 80 million years ago and belongs to the same group of dinosaurs as Velociraptor. True, the creature also has a lot in common with birds. Rahonavis had a retractable sickle-shaped claw on its middle toe, feather cover, and a long, clawed tail similar to Archeopteryx.

The first birds lived in the forest

The first representatives of the class arose and began to master flight, living in the forest on tree branches, jumping and climbing branches, clinging to them with long fingers of the forelimbs with claws. Having spread their wings, they glided in the air from top to bottom along an inclined plane, and also flew short distances by flapping their wings. Only later did some birds begin to adapt to life in the steppes and deserts, on the banks of reservoirs and in other places.

Firstbird - another bird-dinosaur

Archeopteryx for a long time remained the only link between birds and reptiles known to science, but in 1986 the remains of another fossil creature were found that lived 75 million years earlier and combined the characteristics of dinosaurs and birds. Although this animal was named Protoavis (protobird), its evolutionary significance is controversial among scientists.

Many bird species appeared during the Cretaceous period

After Archeopteryx, there is a gap in the fossil record of birds lasting about 20 million years. The following finds date back to the Cretaceous period, when many species of birds appeared, adapted to different habitats. Among the approximately two dozen Cretaceous taxa known from fossils, two are particularly interesting: Ichthyornis And Hesperornis. Both were discovered in North America, in rocks formed on the site of a vast inland sea.

Ichthyornis - an ancient gull

Ichthyornis was the same size as Archeopteryx, its body length was about 50 cm, and it weighed 5 kg. Outwardly, it resembled a seagull with well-developed wings, indicating the ability to fly powerfully. Like modern birds, it had no teeth, but its vertebrae were similar to those of a fish, hence its generic name, meaning “fish bird.” His remains were found in the USA. Ichthyornis lived 65-90 thousand years ago.

Hesperornis - an ancient loon

Hesperornis ("western bird") was 1.5–1.8 m long (up to 2 m) and almost wingless. His weight was 40 kg. With the help of huge flipper-like legs extending sideways at right angles at the very end of the body, it apparently swam and dived no worse than loons. It had "reptilian" teeth, but the vertebral structure was consistent with that typical of modern birds. The remains of Hesperornis were found in the USA. This bird lived 70 thousand years ago.

Modern birds formed 65 million years ago

With the onset of the Tertiary period (65 million years ago), the number of bird species began to increase rapidly. The oldest fossils of penguins, loons, cormorants, ducks, hawks, cranes, owls and some songbirds date back to this period.

Huge flightless birds
In addition to the ancestors of modern species, several huge flightless birds appeared in the Tertiary period, apparently occupying the ecological niche of large dinosaurs. One of them was Diatryma, discovered in Wyoming, 1.8–2.1 m tall, with massive legs, powerful beak and very small, underdeveloped wings.

During the Cretaceous period there lived flying lizards or pterosaurs,

Their wingspan was 7.5 m; they lived in Europe, Africa, North and South America and were carnivores (eating fish and aquatic invertebrates).

Large prehistoric birds resembled ostriches

According to paleontological data, there were large, partially feathered lizards. In 1834, the French explorer Goudeau found half an eggshell in Madagascar so large that it could be used as a water container. Then several giant bones were found in the swamps of the island, which were initially mistaken for the remains of an elephant or rhinoceros. But the bones belonged to a bird that must have weighed at least half a ton. Madagascar ostriches epiornithes (Aepyornithes), reached a height of 5 m, laid eggs 32 cm long and 22 cm wide, containing 8.5 liters of liquid contents. The largest egg in the Epiornis clutch is considered to be 24 cm long and 11 liters in volume.

Roc

The Venetian traveler Marco Polo did not have a chance to visit Madagascar himself, but he also heard amazing stories: “They say that there is a vulture bird there, which appears at a certain time of the year, and in everything the vulture is not the same as we think and as it is portrayed. They say that the vulture is half bird, half lion, and this is not true. Those who have seen him claim that he looks like an eagle, but only very large... On the island they call him Ruk.”

Epiornis were ringed 5 thousand years ago

French zoologists discovered the remains of an apiornis in Madagascar with a bronze ring attached to the bird's leg. Experts came to the conclusion that the signs on the ring are nothing more than an impression of a seal from the era of the most ancient civilization in India - Mohenjo-Daro. made about five thousand years ago. Radiocarbon dating of the bird's bones helped establish its age: it is five thousand years old! In the 3rd millennium BC, the inhabitants of Hindustan made daring sea expeditions. By this time they had accumulated centuries of experience in driving ships, and the Indians had also visited Madagascar. At that time, apiornis were found here in abundance. In the stories of the sailors who returned home, they received a lot of attention.

Do aepornis still exist today?

The eggs, which were found on sand dunes and swamps in the southern part of the island of Madagascar, looked suspiciously fresh. They seemed to have been demolished quite recently. Local residents are sure that people still live in the most dense forests of the island. giant birds, however, they are not easy to see. In Madagascar, there are still huge areas of protected jungle and untrodden swamps; there is enough space for apyornis.

Ostrich dromomys from Australia

Judging by fossil leg bones found in 1974 near Alice Springs, flightless Dromomis stirtoni, a giant, ostrich-like bird that lived in central Australia from about 15 million to 25,000 years ago, reaching a height of 3 m and weighing about 500 kg.

Moa ostrich from New Zealand

A giant bird that looks like an ostrich moa (Dinornis maximus), living on the islands of New Zealand, presumably until the beginning of the 19th century, was probably even greater in height - 3.7 m, and weighed about 230 kg.

When did Australia's last giant birds go extinct?

Analysis of ancient eggshells suggests Australia's enormous flightless birds went extinct 45,000 to 55,000 years ago after humans scorched their habitat.

What did the first birds eat?

An international team of scientists has analyzed hundreds of eggshell fragments from an extinct flightless bird called Geniornis that lived 130,000 to 50,000 years ago. Carbon isotopes from eggshells reveal what the birds ate when they laid their eggs. It was discovered that Geniornis's diet was strict and always included grass.

The largest ancient bird capable of flight

At the end of the Tertiary period (1 million years ago) and throughout the early Pleistocene, or glacial era, the number and diversity of birds reached a maximum. Many of today's species emerged, as well as others that later became extinct. Teratornis incredibilis from Nevada (USA), a huge condor-like bird with a wingspan of 4.8–5.1 m; was probably the largest known bird capable of flight.

Difference between birds and mammals

Characteristics specific to the class of birds are primarily associated with the ability of these animals to fly, although some of their species, such as ostriches and penguins, lost it during their later evolution. What makes them stand out even more is their feathers, which are not found on any other animal. They differ from most mammals in that they lay eggs.

Extinct and endangered birds

The first documented case of this kind was the destruction of the dodo. Mauritian dodo Raphus cuculatus large flightless pigeons, resembling turkeys in appearance, three species of which lived on three islands of the Mascarene archipelago in the Indian Ocean (Mauritius, Reunion and Rodrigues). They were quickly destroyed by humanity almost immediately after their discovery: the archipelago was discovered in 1507, the last dodo was seen in Mauritius in 1681. In the 174 years after the discovery of Mauritius by Europeans in 1507, the entire population of these birds was exterminated by sailors and the animals they brought on their ships. On the island of Reunion, the last bird was killed in 1750, on the island of Rodrigues last bird also did not live to see the end of the 18th century.

The most famous extinct birds

Passenger pigeon
In 1914, Martha, the last representative of a previously large genus, died at the Cincinnati Zoo (North Carolina, USA). passenger pigeons (Ectopistes migratorius). Passenger pigeons were mercilessly exterminated for meat.

The first species to become extinct at the hands of man North America
...became great auk (Alca impennis), extinct in 1844. It also did not fly and nested in colonies on the Atlantic islands near the continent. Sailors and fishermen easily killed these birds for meat, fat and to make bait for cod.

Soon after the disappearance of the great auk, two species in the east of the North American continent became victims of humans. One of them was Carolina parrot (Conuropsis carolinensis). Farmers killed these flocking birds in large numbers as thousands of them regularly raided gardens.

100 species of birds have disappeared
Since 1600, perhaps 100 bird species have become extinct worldwide. Most of them were represented by small populations on sea islands. Often incapable of flight, like the dodo, and almost unafraid of man and the small predators brought by him, they became easy prey for them.

Many species of birds are also on the verge of extinction. Currently, many species of birds are also on the verge of extinction or, in best case scenario, feel threatened by him. In North America, the California condor, yellow-legged plover, whooping crane, Eskimo curlew and (possibly now extinct) ivory-billed woodpecker are among the most distressed species. In other regions, the Bermuda typhoon, the Philippine harpy, the kakapo (owl parrot) from New Zealand, a flightless nocturnal species, and the Australian ground parrot are in great danger.

Birds at risk of extinction

IN natural conditions only one lives nowadays blue macaw (Cyanopsittaspixii), however, approximately 30 of these birds are kept in captivity.

Hawaiian songbird, lepidopteran mojo (Moxobracattus), considered completely extinct and rediscovered only in 1960, apparently, is represented by only 2 pairs of individuals.

There are less than 20 survivors in the world (mostly in captivity) Red-legged Ibis (Nipponia nippon), but they are all apparently too old to reproduce.

As a result of uncontrolled hunting New Zealand owl parrot (Strigops habroptilus) was on the verge of extinction. The second reason for its extinction is that this flightless bird cannot escape from predators, so only 10 specimens remain alive.

Nowadays, only a few exist in natural conditions. California condors, bred in captivity and released in 1992.

Other known extinct bird species include

Labrador eider Camptorhynchus labradorius.
Samoan moorhen Gallinula pacifica.
White plume Porphyrio albus.
Mauritius blue pigeon Alectroenas nitidissima.
Norfolk ground pigeon Hemiphaga argetraca.
Slender-billed nestor Nestor productus.
Cuban macaw Ara tricolor.
Cayman bluebird Turdus ravidus.

The birds listed above found themselves in an unenviable position mainly due to the fault of humans, who brought their populations to the brink of extinction through uncontrolled hunting, ill-considered use of pesticides or radical transformation of natural habitats.

26 species of birds and 132 species of mammals are now on the verge of extinction.

The hypothesis that birds evolved from reptiles was put forward in the second half of the 19th century. However, the question of the origin of birds still causes heated debate among paleontologists.

Ancestors

The problem is the lack of avian ancestors or the “first bird.” The found prints are interpreted differently and not a single find is definitely considered the ancestor of modern birds. Briefly talking about the origin of birds, we should describe the most significant finds that give an idea of ​​​​the origin of birds from reptiles.

• Archeopteryx . The very first find discovered in Bavaria in 1861. Based on the discovered prints, a small creature the size of a crow was described that lived about 150 million years ago. The presence of feathers indicates that they are birds. Anatomically more similar to a reptile. I couldn’t fly fully. Perhaps he was just planning from branch to branch. However, Archeopteryx is classified in the class Birds, subclass Lizard-tailed.

Rice. 1. Archeopteryx is the most ancient bird.

• Enantiornis . The remains of ancient birds were discovered in Argentina in 1981. They lived 70-65 million years ago and had the characteristics of birds: they had well-developed wings and could fly. The presence of teeth and the structure of the skeleton make the find similar to Archeopteryx.
• Confuciusornis . The oldest bird to independently lose teeth was found in China. Lived about 120 million years ago. The beak was covered with a horny sheath. In some respects, the skeleton is similar to modern birds.
• .

  They lived between 168 and 66 million years ago. This extensive family, belonging to the suborder Theropods, order Saurischians, contains several species of feathered dinosaurs (Deinonychus, Utahraptor, Sinornithosaurus). The most significant is Microraptor, or the “four-winged dinosaur,” which had wing-like surfaces on its fore and hind limbs.

  

  Rice. 2. Dromaeosaurids.

  • . Found and described in China in 2009. Belongs to the Troodontidae family, Lizard-pelvic order. Lived 167-155 million years ago. It reached 30-40 cm in length and weighed 100 g. It had plumage, a long tail, and a beak.

  

  Rice. 3. Anchiornis.

  There are other forms that indicate the presence of feathers in dinosaurs. For example, Caudipteryx, which lived 120-125 million years ago, had fan feathers on its tail, which most likely served to attract a sexual partner.

  Evolution is not a linear process. Found forms indicate attempts different types master the airspace. Exactly which lineage the birds originated from remains to be seen.

  Hypotheses

  Analysis of the finds allowed us to formulate a hypothesis of the origin and evolution of birds from their dinosaur ancestor. The first birds appeared during the Jurassic period (between 201 and 145 million years ago). Troodontids and dromaeosaurids - "feathered dinosaurs" - were long thought to be the closest ancestors of modern birds.

  Reptiles acquired the ability to fly after mastering trees. By retaining claws on their front limbs and powerful hind limbs, dinosaurs could climb trees. In the process of evolution, they acquired the ability to glide using modified scales, which later became feathers. According to another hypothesis, reptiles learned to fly “from the ground”, jumping after insects.

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  The well-coordinated “dinosaur” hypothesis began to have opponents when, in 1991, in Texas, Shankar Chatterjee found two fossil birds - protoavis, who lived 220-200 million years ago, i.e. 50-70 years earlier than Archeopteryx. Unlike the "Bavarian bird", Protoavis has more features in common with modern birds. This means that theropods that lived later than Protoavis are at best “brothers” and not direct ancestors of birds. This hypothesis was actively supported by paleontologist Evgeny Kurochkin.

  Chatterjee's find was met with harsh criticism. Many paleontologists believe that Chatterjee found a chimera - bones belonging to different animals. It is unscientific to base a hypothesis on such data.

  A reptile similar to Archeopteryx, Scansoriopteryx, is classified by some paleontologists as a bird, which also casts doubt on the hypothesis of the origin of birds from dinosaurs.

  What have we learned?

  Some species of dinosaurs had feathers, which may indicate the origin of birds from dinosaurs. At the same time, several finds refute this hypothesis and suggest that birds descended from a common ancestor with dinosaurs.

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Forest inhabitants of the Chinese province of Liaoning 130 million years ago. A small four-winged dinosaur, Microraptor gooi, hovers in the foreground. Cathayornis flying on the right are also not considered birds. But on the left on the branch sits Confuciusornis, representing one of the evolutionary lines close to birds. It is obvious that various groups of feathered animals tried to master the air environment in the Cretaceous period.

Until recently, the early evolution of birds represented perhaps the darkest chapter in the fossil record. And although recent paleontological discoveries have clarified a lot, it is not possible to read it completely. What is known is that birds evolved from reptiles. But from which ones exactly? The direct ancestors of modern birds have never been found, and plumage and the ability to fly arose repeatedly in various animals of the Mesozoic era. There are more than enough hypothetical ancestors: among them are pseudosuchians, ornithosuchians, pterosaurs, dinosaurs and even crocodiles. But Archeopteryx, familiar to everyone from the picture in a school textbook, has to be crossed out from this list.

Birds, along with insects, are the main inhabitants of the Earth's air spaces. Several devices allow them to take to the skies and control their movements in flight. First, a special skeleton. A complex wing is capable of holding the entire weight of the body in the air. Its swing movements depend on the structure of the shoulder girdle, formed by the scapula, coracoid, sternum and clavicles fused into a fork. There, for example, there is a three-bone hole through which passes the tendon of the muscle that lifts the wing up after it is lowered. To hold the tail feathers, which serve as a rudder in flight, the end of the spine formed a short and wide bone - the pygostyle. Secondly, plumage helps birds fly. Controllability in flight is provided by very specific feathers: flight feathers and tail feathers. But there are also feathers, the purpose of which is different: they create a streamlined body shape for birds both during flight and when diving, serve as a heat-protective cover and, being brightly colored, help in communication between relatives.

Apart from birds, the only vertebrates currently able to fly are bats and fruit bats. However, they have a fundamentally different wing structure and no feathers, which makes their flight unlike that of a bird. In the past, the variety of flying and feathered creatures was extremely large. In addition to the long-known pterosaurs and archeopteryx, paleontologists have discovered a large number of unusual species whose existence they did not even suspect. It seems that the animal world had no shortage of people willing to conquer the sky.

There are two main hypotheses for animals acquiring flapping flight: from faster running on the ground or from jumping and gliding from some elevated places - trees, rises in the mountains. The latter hypothesis received indirect confirmation after the discovery of various feathered dinosaurs in China, in the Liaoning province. Now most scientists believe that flying species came from the environment of the forest-dwelling, probably some very small, no larger than a pigeon, species of reptiles and birds. Their descendants quickly passed the primitive stage - gliding from elevated places - and learned to fly for real. How long did all this take, how many species changed before birds acquired flight? No one will say, since the flying creatures found by paleontologists may not have been the first, and the very beginning of the evolution of birds is still hidden from us.

For a long time it was believed that the plumage of birds is the scales of reptiles modified over millions of years of evolution. However, the results of the latest research cast doubt on this. Both plumage and scales, like all integumentary formations in vertebrates, originate from the cells of the outer layer of the skin - the epidermis. Reptile scales are composed of so-called alpha-keratin, a protein with short peptide chains. It is formed from protruding areas of one outer layer of the epidermis. During the development of feathers in birds, a tubercle of the epidermis also first appears, but it is formed not by one, but by its two outer layers. Then this tubercle sinks inside the skin, forming a kind of sac - a follicle, from which the feather grows. Moreover, the material for the feather is slightly different - beta-keratin, composed of long peptide chains, which means it is more elastic and strong, capable of supporting the feather plates. Alpha-keratin is also present in birds; it is used to form the cover of the beak, claws and scales on the tarsus. In addition, the feathers of birds have a tubular structure, and the scales of reptiles are solid. Apparently, the feather is an evolutionary innovation that has proven its usefulness over time.

Plumage that easily acquires different shape and coloring, revealed almost unlimited possibilities To various types flight, development of signal and identification structures, development of many ecological niches. It was plumage that helped birds achieve the enormous diversity that we now see. Almost ten thousand species are more than all other land vertebrates.

If most feathered dinosaurs couldn't fly, why did they need down or feathers? Clearly not for flying. In any case, not immediately for the flight. It is possible that various downy formations arose among predatory lizards as a thermal insulation cover, as indicated by paleoclimate data. In the middle and end of the Triassic period (230-210 million years ago), when the first dinosaurs appeared, a cold snap occurred on Earth. Along the outskirts of the huge continent of Pangea, the only one at that time, latitudinal climatic zones with a cool, humid climate appeared. The animals that lived there adapted to the cold, including with the help of plumage. On the contrary, the center of Pangea was occupied by dry and desert areas with high levels of solar radiation, since cloudiness in those parts was rare. To protect against radiation, reptiles again used down and feathers. Over time, the feathers at the ends of the forelimbs, on the tail and on the head could turn into elongated feathers that served as decorations or identification marks. They became the basis for the appearance of flying feathers in some dinosaurs. In a similar way, other reptiles could have acquired plumage, among which were the distant ancestors of birds.

Doesn't appear in birds

For almost 150 years, since the first discovery, Archeopteryx was considered the progenitor of modern birds. In fact, other than knowledge about this creature, scientists for a long time had no other information about the origin of birds. It would seem that such features as plumage and wings undeniably indicated that Archeopteryx was the oldest bird. On the other hand, in terms of the structure of the skull, spine and other parts of the skeleton, it was similar to predatory dinosaurs. These observations gave rise to the hypothesis about the origin of birds from ancient lizards, which has now become especially popular.

As often happens in science, an alternative hypothesis also found support. Long-expressed doubts about the direct relationship of Archeopteryx and birds (they are too different anatomically) have turned into conviction, since since the early 1980s, paleontologists have found feathered dinosaurs, ancient birds, and their close relatives. New skeletons of Archeopteryx were also found. Today, ten of them are known, all of Upper Jurassic age (145 million years ago) from the Altmühl River in Bavaria. The last specimen, which is better preserved than the others, described at the end of 2005, finally convinces that Archeopteryx descends from predatory dinosaurs, but has nothing to do with modern birds. He is something else: not a dinosaur, but not a bird either. I had to look for another candidate for the role of the ancestor of birds.

Dinosaur down jacket

The existence of feathered dinosaurs has long been suspected, but there has been no evidence of it. They appeared in the 1990s in China, in Liaoning province. There, paleontologists discovered a whole cemetery of forest flora and fauna 130-120 million years old. What makes the event unique is the natural area uncovered by excavations. Marine or near-aquatic communities of animals and plants are usually available for study due to better conditions burials. Forest, steppe or mountain inhabitants of the past most often are not preserved in a fossil state, because they are quickly converted into dust by bacteria. And here is a snapshot of forest life in the mid-Cretaceous period, recorded by volcanic ash.

The first discovered skeleton of a lizard with short grooves similar to fluff along the contour of the entire body - Sinosauropteryx prima - caused numerous disputes: not everyone agreed that the small grooves on the fossilized clay were from fluff. Then they dug up another creature, which, no doubt, already had feather imprints on its tail and front legs. For its resemblance to Archeopteryx, it was given the name Protarchaeopteryx robusta. On the limbs of another dinosaur, Caudipteryx zoui, the feathers grew even thicker, and the body was covered with fluff.

Now more than a dozen lizards have been described, with surprisingly varied feathers: from short down to real asymmetrical feathers on the limbs, indicating the ability to fly. In addition, the skeleton of these predatory dinosaurs revealed some features characteristic only of birds: a fork, hook-shaped processes on the ribs, and a pygostyle. But still, these were not birds, but small predators that moved mainly by running. With long tails, toothy, covered with scaly skin, with shortened front legs and long clawed fingers. Judging by the structure of the skeleton, most of them could not really fly, that is, flap their wings. Only one species is known that has risen one step higher. This is Microraptor gui - an interesting specimen of a small dromaeosaur, found there, in Liaoning. All in fine plumage, with a crest on the head. Its front legs were covered with asymmetrical (with narrow outer and wide inner webs) flight feathers exactly like those of birds. The hind legs were also covered in flying feathers, longer on the metatarsus and shorter on the lower leg. It turns out to be nothing more than a four-winged feathered dinosaur that could fly from tree to tree. However, he turned out to be a poor flyer. In the absence of binocular vision (when the field of view of both eyes overlaps), Microraptor could not accurately target its landing site and descended into the trees, apparently rather awkwardly.

It would seem that we can assume that birds descended from predatory dinosaurs soaring among the trees. However, too significant anatomical differences between them do not allow this to be done. So there is no need to rush and record feathered dinosaurs as the ancestors of birds.

Established competitors

Living side by side with feathered dinosaurs were enantiornis, which in Greek means “anti-birds,” creatures especially important for understanding the evolution of birds. Judging by the findings, this was the largest and most diverse group of flyers that lived in the Cretaceous period.

Externally, enantiornhis closely resembled modern birds. Among them there were small and large species, toothless and toothed, running, waterfowl, arboreal, and, most importantly, they all flew perfectly. There was also a lot of familiarity in the skeleton: the same bones of the wing, torso and hind limbs. Only some things articulate differently in the shoulder blade, some in the heel, lower leg and spine. Small differences at first glance. And the end result is a different wing lifting system and footwork. Most real birds can move their paws in different directions: turn inward, turn outward. This helps predators, eagles and falcons, to deftly grab and hold their prey. The legs of enantiornis (many of which, by the way, were also predators) are designed differently, which is why they walked on the ground, rather, clumsily waddling from side to side, like geese. All this greatly distances Enantiornis from real birds. It turns out that their external similarity is formal. Just as the tail of the aquatic lizards ichthyosaurs is similar to the tail of fish, so the paws and wings of enantiornis are similar to the paws and wings of real birds.

Many anatomical features make Enantiornis similar to carnivorous dinosaurs. This is confirmed by the findings of embryos inside fossil eggs in Mongolia. It turned out that the bones of the skeleton were finally formed in these primitive birds very early. The joints of the unhatched chicks were already bone, like dinosaurs, and not cartilaginous. In the chicks of modern birds, the joints remain cartilaginous for a long time and only after a few months are replaced by growing bone. In addition, cross-sections of enantiornis bones show lines of growth retardation, similar to growth rings on tree trunks. This suggests that their bones did not grow to their final size in one season, but were formed in cycles over several years, slowing down during the cold seasons of the year. This means that antibirds could not maintain their body temperature at a constant level - just like reptiles. Apparently, it was the carnivorous dinosaurs that were the ancestors of enantiornis. About 67 million years ago, both of them became extinct, leaving no descendants behind.

An ancestor who may not exist

For a long time it was believed that real birds, or fan-tailed birds, as they are also called, appeared at the beginning of the Cenozoic era, that is, no earlier than 65 million years ago. And suddenly finds 100 and 130 million years old began pouring in from the United States, Mongolia and China. At first they didn’t even believe the age determinations, but subsequent work confirmed that, yes, during the time of dinosaurs and enantiornis, fan-tailed birds were already found. They looked just like modern ones and even achieved some variety. Where did they come from if the feathered and flying creatures discussed above are not suitable as their ancestors? Now there is only one assumption.

In 1991, American paleontologist Shankar Chatterjee described an unusual creature he found in Texas, which was in many ways similar to birds. Its age is 225 million years, which is 80 million older than the age of Archeopteryx. The creature was called Protoavis texensis - “proto-bird”, and not without reason. His voluminous skull contained quite big brain with hemispheres and cerebellum, which other vertebrates did not have in the Late Triassic time when he lived. Judging by the structure of the skull, Protoavis had binocular vision and wide-set large eyes, which indicates its ability to hunt deftly and navigate well in the surrounding world, as is typical of birds. In general, the skeleton of Protoavis has many features similar to fan-tailed birds, but the proportions of the body, short and powerful limbs, and the position of the center of gravity indicate that it could not fly. And he apparently had no feathers. Despite this, Protoavis is more similar to a real bird than Archeopteryx, and at this moment it is Protoavis that can be considered the closest ancestor of modern birds. If this is so, then their evolution should be carried out not from dinosaurs, but from more ancient reptiles, united in the group of archosaurs.

The discovery of protoavis made it possible to find an answer to another question: how do birds differ from dinosaurs? Because birds expend enormous amounts of energy to fly, their metabolic rate is much higher than that of reptiles. In birds, oxygen consumption during metabolism per kilogram of weight is 3-4 times higher than in reptiles. Since the metabolic rate is high, therefore, toxins must be removed from the body quickly. This requires large, powerful buds. In modern birds, there are three deep cavities in the pelvic bones, in which these large buds are located. The same cavities for the kidneys are also present in the pelvic bones of Protoavis. Obviously, his body had a high level of metabolism, unusual for reptiles.

Everything would be fine, but the reconstruction of Protoavis does not inspire confidence in many paleontologists. Its remains were interspersed with the bones of other reptiles; in such conditions, it is not surprising to confuse and count parts of two or even several different animals as a single creature. In general, for final conclusions we must wait for other finds, and modern birds will remain without direct ancestors for now.

However, like ancient birds without direct descendants. Because it is not possible to trace the evolution of birds sequentially from beginning to end. There are still plenty of gaps. In particular, no intermediate links have been found between the ancient fantails, which still retained reptilian features—teeth growing from the alveoli, abdominal ribs, and a long row of vertebrae in the tail—and modern groups of birds. Suddenly, as if out of nowhere, ancient geese, loons, albatrosses, cormorants and other aquatic birds appeared at the end of the Mesozoic era.

As a hypothesis

So, we saw a number of amazing feathered creatures that lived on Earth at least at the end of the Mesozoic, from 145-65 million years ago. At that time, the world was full of animals trying to master the airspace. In addition to the ubiquitous enantiornis, the seas of North America were inhabited by toothy, gannet-like ichthyornis. Hesperornis lived in the Late Cretaceous in the seas of ancient Eurasia. In Europe, there were gargantuavis, a bird of unknown origin the size of a turkey. The forests of Mongolia and China were inhabited by arboreal Ambiorthus, Liaoningornis and feathered dinosaurs. And there are many more single forms whose position on the evolutionary tree of birds is difficult to establish. Only two branches can be clearly traced: from protoavis to fan-tailed birds and from feathered dinosaurs to Archeopteryx and then enantiornis.

There are a number of fossil forms known that have not progressed beyond planning. While real flapping flight was achieved only by pterosaurs (we are not discussing them here, since they are not at all related to birds), microraptor gooi, enantiornis and real fan-tailed birds. All of them were successful in mastering the air environment. Pterosaurs reigned in the air for 160 million years, enantiornithes for at least 80 million years. Both of them were probably surpassed in competition by fan-tailed birds, which have spread widely across the planet in the last 65 million years.

Over the past couple of decades, paleontologists have shown that parallel evolution is a widespread path among living things. There were several attempts among invertebrates to become arthropods, among ancient fish to reach land and become amphibians, among reptiles to become mammals, among plants to acquire flowering and become angiosperms. But usually only one or two of them were successful in the future.