The origin of Archeopteryx. Archeopteryx, all about Archeopteryx, about Archeopteryx, Jurassic dinosaurs, the era of the dinosaurs, Archeopteryx description

Archeopteryx is an extinct vertebrate animal dating back to the Late Jurassic period. According to morphological characteristics, the animal occupies a so-called intermediate position between birds and reptiles. According to scientists, Archeopteryx lived about 150-147 million years ago.

Description of Archeopteryx

All finds, one way or another connected with the extinct Archeopteryx, relate to the territories in the vicinity of Solnhofen in southern Germany. For a long time, even before the discovery of other, more recent finds, scientists used to reconstruct the appearance of the alleged common ancestors of birds.

Appearance

The structure of the skeleton of Archeopteryx is usually compared with the skeletal part. modern birds, as well as deinonychosaurs, which belonged to theropod dinosaurs, which are the closest relatives of birds in terms of phylogenetic position. The skull of an extinct vertebrate animal carried tapered teeth, according to morphological characteristics, they are most similar to the teeth of ordinary crocodiles. The premaxillary bones of Archeopteryx were not characterized by fusion with each other, and its lower and upper jaws were completely devoid of the ramphoteca or corneous sheath, so the animal lacked a beak.

The large occipital foramen connected the cranial cavity and the vertebral canal, which was located behind the skull. The cervical vertebrae were biconcave posteriorly and anteriorly, and also had no saddle articular surfaces. The sacral vertebrae of Archeopteryx did not have fusion with each other, and the sacral vertebral section was represented by five vertebrae. A bony and long tail was formed by several non-accrete caudal vertebrae of Archeopteryx.

The ribs of Archeopteryx did not have hook-shaped processes, and the presence of ventral ribs, typical of reptiles, is not found in modern birds. The clavicles of the animal fused together and formed a fork. There was no fusion on the ilium, pubic, and ischial pelvic bones. The pubic bones were turned slightly backward and ended in a characteristic "boot" extension. The distal ends on the pubic bones joined together, resulting in the formation of a large pubic symphysis, which is completely absent in modern birds.

The rather long forelimbs of Archeopteryx ended in three well-developed toes formed by several phalanges. The fingers had strongly curved and rather large claws. The wrists of the Archeopteryx had a so-called lunate bone, and the other bones of the metacarpus and wrist did not fuse into a buckle. The hind limbs of the extinct animal were characterized by the presence of a tibia formed by the tibia and tibia of approximately equal length, but the tarsus was absent. The study of the Eissstadt and London specimens allowed paleontologists to establish that the thumb was opposed to the other fingers on the hind limbs.

The first drawing of a Berlin copy, made by an unknown illustrator back in 1878-1879, clearly showed feather prints, which made it possible to classify Archeopteryx as a bird. Nevertheless, bird fossils with feather prints are extremely rare, and their preservation became possible only due to the presence of lithographic limestone in the places of finds. At the same time, the preservation of the imprints of feathers and bones in different specimens of the extinct animal is not the same, and the most informative are the Berlin and London specimens. The plumage of Archeopteryx in terms of its main features corresponded to the plumage of extinct and modern birds.

Archeopteryx had tail, flight and outline feathers that covered the body of the animal.... The tail feathers and flight feathers are formed by all the structural elements characteristic of the plumage of modern birds, including the feather shaft, as well as the barbs and hooks extending from them. For the flight feathers of Archeopteryx, asymmetry of the webs is inherent, while the tail feathers of the animals were less noticeable asymmetry. There was also no separate movable bundle of thumb feathers located on the forelimbs. There were no signs of feathering on the head and upper part of the neck. Among other things, the neck, head and tail were curved downward.

A distinctive feature of the skull of pterosaurs, some birds and theropods is represented by thin meninges and small venous sinuses, which makes it possible to accurately assess the surface morphology, volume and mass of the brain, which were possessed by extinct representatives of such taxa. Scientists at the University of Texas were able to perform the best brain reconstruction of an animal to date using X-ray tomography back in 2004.

The brain volume of Archeopteryx is approximately three times that of similarly sized reptiles. The cerebral hemispheres are proportionally smaller and also not surrounded by olfactory tracts. The shape of the cerebral visual lobes is typical for all modern birds, and the visual lobes are located more frontally.

It is interesting! Scientists believe that the presence of avian and reptilian features can be traced in the structure of the brain of Archeopteryx, and the increased size of the cerebellum and visual lobes, most likely, was a kind of adaptation for the successful flight of such animals.

The cerebellum of such an extinct animal is comparatively larger than that of any related theropods, but noticeably smaller than that of all modern birds. The lateral and anterior semicircular canals are located in a position typical of any archosaurs, but the anterior semicircular canal is characterized by significant elongation and curvature in the opposite direction.

Archeopteryx dimensions

Archeopteryx lithofraphica from the class Birds, the order Archeopteryx and the Archeopteryx family had a body length within 35 cm with a mass of about 320-400 g.

Lifestyle, behavior

Archeopteryx were the owners of fused collarbones and a body covered with feathers, so it is generally believed that such an animal could fly, or at least glide very well. Most likely, on its rather long limbs, Archeopteryx quickly ran along the surface of the earth until the updrafts of air picked up his body.

Due to the presence of plumage, Archeopteryx most likely very effectively supported temperature regime bodies than they flew. The wings of such an animal could well serve as a kind of nets used to catch all kinds of insects. It is assumed that Archeopteryx could climb fairly tall trees using the claws on their wings for this purpose. Such an animal most likely spent a significant part of its life in trees.

Life expectancy and sexual dimorphism

Despite several found and well-preserved remains of Archeopteryx, it is not possible to establish reliably the presence of sexual dimorphism and the average life span of such an extinct animal at the moment.

Discovery history

To date, only a dozen skeletal specimens of Archeopteryx and a feather print have been discovered. These findings of the animal belong to the category of thin-layered limestones of the Late Jurassic period.

Key Finds Related to Extinct Archeopteryx:

• an animal feather was discovered in 1861 near Solnhofen. The find was described in 1861 by the scientist Hermann von Mayer. Now this feather is very carefully preserved in the Berlin Museum of Natural History;
• a London headless specimen (holotype, BMNH 37001), discovered in 1861 near Langenaltime, was described two years later by Richard Owen. This find is now on display at the London Museum of Natural History, and the missing head was restored by Richard Owen;
• a Berlin specimen of the animal (HMN 1880) was found in 1876-1877 at Blumenberg, near Eichstät. Jacob Niemeyer managed to exchange the remains for a cow, and the specimen itself was described seven years later by Wilhelm Dames. Now the remains are kept in the Berlin Museum of Natural History;
• the body of a Maxberg specimen (S5) was discovered presumably in 1956-1958 near Langenaltime and described in 1959 by the scientist Florian Geller. Detailed study belongs to John Ostrom. For some time this copy was shown in the exposition of the Maxberg Museum, after which it was returned to the owner. Only after the death of the collector was it possible to assume that the remains of the extinct animal were secretly sold by the owner or stolen;
• The Harlem or Teyler specimen (TM 6428) was discovered near Rydenburg in 1855, and described twenty years later by the scientist Meyer as Pterodactylus crassipes. Almost a hundred years later, the reclassification was made by John Ostrom. Now the remains are in the Netherlands, in the Teyler Museum;
• The Eichstät animal specimen (JM 2257), discovered around 1951-1955 near Workerszell, was described by Peter Welnhofer in 1974. Now this specimen is in the Jurassic Museum of Eichshtet and is the smallest, but well-preserved head;
• Munich specimen or Solnhofen-Aktien-Verein with sternum (S6) was discovered in 1991 near Langenalheim and described by Welnhofer in 1993. The copy is now in the Munich Paleontological Museum;
• the ashhofen specimen of the animal (BSP 1999) was found in the 60s of the last century near Eichstät and described by Welnhofer in 1988. The find is kept in the Museum of the Burgomaster Müller and may belong to the Wellnhoferia grandis;
• The Müllerian fragmentary specimen, discovered in 1997, is now in the Müllerian Museum.
• A thermopoly specimen of the animal (WDC-CSG-100) was found in Germany and was kept by a private collector for a long time. This find is distinguished by the best preserved head and feet.

In 1997, Mauser received a message about the discovery of a fragmentary specimen from a private collector. Until today, this copy has not been classified, and its location and owner's details have not been disclosed.

The eternal problem of paleontological evidence of biological evolution is the search for transitional forms, namely, intermediate links in the phylogenetic lines of modern life forms. In this vein, the "sacred cow" is considered to be a transitional form from reptiles to birds - Archeopteryx (translated from Greek it means "ancient wing"). But recent research, which we'll talk about later, has shaken these long-held beliefs. Still, Archeopteryx is a bird or a reptile? We will try to answer this question.

History of finds

Today paleontology has at its disposal more than ten skeletal prints of this creature, and they all belong to the late Jurassic period (200-150 million years ago) and were found in Austria and Germany.

The most famous image and print of Archeopteryx is the Berlin specimen, which is kept in the Natural History Museum Berlin. This print was discovered in 1876 by archaeologist Jacob Neumer, who traded it for a cow. But it was described by another archaeologist, Wilhelm Dames, in 1884. It was from that time that Archeopteryx, a transitional form from reptiles to birds, entered the history of paleontology.

The best-preserved specimen, however, is Thermopolis. For a long time it was in a private collection and only in 2007 was it described in detail. We can say that only these two specimens have practically all parts of the skeleton in relatively complete safety.

No longer a reptile, but not yet a bird

This creature has been described as an intermediate link between cold-blooded reptiles and warm-blooded birds. As a reptile, Archeopteryx has;

• tapered teeth, very similar in structure to crocodiles;
• tail of the skeleton;
• four-phalangeal fingers on the forelimbs with pronounced claws.

There are other features of the skeleton that bring it closer to reptiles (the back of the head, the structure of the lower leg and ribs).

The feather plumage, which is clearly imprinted in skeletal impressions, is considered primarily a feature of birds in Archeopteryx. Flight feathers and tail feathers, with grooves like those of modern ones, leave no doubt that we have one of the ancestors of birds before us. There are other features of the skeleton, namely the fork - the fused clavicles. Separately, it is worth mentioning the size of the brain of Archeopteryx (this is rather controversial evidence, but it is), its volume is 3 times that of reptiles.

If he lived today

If this forebird lived now, then we would see that Archeopteryx is a creature the size of a dove, most likely dark or black in color, and with feathered legs. At the same time, he has well-developed muscles, and the asymmetric plumage contributes to fast flight, but difficult landing and heavy takeoff. The anatomical features of the skeleton indicate that this half-bird-half-lizard uses active flight with flapping wings for a short time and sporadically. Most likely, Archeopteryx would now live on rocky cliffs of rivers and it would be from a height that they would begin their flight with planning elements. Presumably, these animals would lead a solitary and nocturnal lifestyle, only occasionally gathering in groups. Archeopteryx food is worms, insects, small reptiles. Only he would not peck at them, but would direct himself into the toothy beak with clawed forelimbs.

Avian genesis in evolution

Since 1867, when the English zoologist and supporter of Darwinism Thomas Henry Huxley introduced Archeopteryx into biology as a transitional form in the evolution of birds, this point of view, although it was subjected to periodic criticism, has retained its position. Subsequent fossil finds only added value in substantiating the phylogenetics of birds. In paleontology, the point of view persisted that Archeopteryx was like Tutankhamun in Egyptology. But…

The works of the American paleontologist Shankar Chatterjee, published in 1991 on the finds in Texas of skeletal prints called protoavis, brought a certain amount of confusion to the established system of views on the evolution of birds. Protoavis was more like modern birds than Archeopteryx, and lived 70-75 million years earlier.

In 2010, a find appeared, which further shook the "pedestal" of the half-lizard-half bird. In northeastern China, skeletal fossils of a feathered creature have been discovered that lived 10 million years earlier than Archeopteryx. A group led by Xing Xuya, a professor at Linying University (China), found the remains of a feathered dinosaur. The studies and conclusions of these scientists boil down to the statement that Archeopteryx is a representative of a dead-end branch of evolution and is not at all the ancestor of birds.

Other valid doubts

Michael Hubbib, a paleontologist at the University of Southern California, cites data on the structural analysis of the Archeopteryx skeleton, according to which this "miracle in feathers" did not even know how to fly.

The authority of Archeopteryx is undermined by numerous studies of the evolution of the brain of ancient reptiles and birds. Although the ratio of brain mass to body mass in birds is greater than that of dinosaurs, the "icon of paleontology" had a brain volume even less than its contemporaries, the dinosaurs.

Feathers are not birds

But the study of the feather of Archeopteryx, which was carried out with the help of a scanning microscope by paleontologist from England Alik Walker, gave shocking information that the feathers of the great bird and modern birds are fundamentally different in their structure. What was previously thought to be grooves similar to the grooves on feathers of modern birds, in Archeopteryx, turned out to be only ridges to increase mechanical strength. And if the main bird feature does not at all bring Archeopteryx closer to modern birds, then who is he?

Summing up

And today it raises many questions. Most evolutionists say that flight fitness has emerged at least twice in the evolutionary arena. And it is not so important how long and at what distances the extinct Archeopteryx flew actively or planned, its findings can still be considered conditionally transitional forms from lizards to birds.

And let the question arise: "How could such small and vulnerable creatures survive in the era, but their existence is beyond doubt. The comparative paucity of paleontological data does not make it possible to recreate their appearance and lifestyle, to fill in all the blank spots in this evolutionary history. Let's leave them alone." replenishment of science fiction writers, at least for now.

Archeopteryx is an ancient bird that lived during the Jurassic period, outwardly this animal resembled a modern crow. Scientists believe that Archeopteryx was an intermediate link between birds and reptiles. Undoubtedly, Archeopteryx, which has signs of birds, was strikingly different from the animals of its time and habitat. The ability to fly was his unique ability.

Today it is known that all varieties of Archeopteryx lived in the lands of modern Germany about 155 million years ago, back in the Jurassic period.

The name of this amazing creature is translated as "ancient wing", and this testifies to its relationship with birds. But the presence of biconcave vertebrae, a long tail, and jaws with teeth may indicate that Archeopteryx can also be attributed to ancient reptiles. Another surprising feature: Archeopteryx had wings and was covered with feathers, but it lacked a beak.

In 1855, the very first specimen of this bird / reptile hybrid was found. Renowned paleontologist Dave Haarlemsky named this animal Archeopteryx after a museum in the Netherlands where the remains of this creature are kept to this day. All subsequent finds of the remains of Archeopteryx hardly differed from each other, but had a number of peculiarities.

One of them is a peculiar structure of the skull, inside which there were sharp teeth, but the beak was completely absent. Also, the structure of the ribs, limbs and vertebrae had significant differences, which allowed scientists to attribute this ancient animal to the class of reptiles.

But there is a paradox: the presence of plumage and the possibility of aerodynamic movement of this animal may indicate that Archeopteryx can be remotely attributed to birds.

Scientists have come to the conclusion that Archeopteryx is a conditional intermediate between birds and reptiles, this animal inherited its abilities and traits from both. Take, for example, the structure of their brain: it is built on the principle of the brain of amphibians, and they have well-developed cerebellum and zones responsible for vision, which determines good flight ability.

But to call such a movement of this animal a flight in modern understanding can be very conditional. After all, the fact is that Archeopteryx could not fly in our understanding, he could only glide through the air from branch to branch. He did not know how to flap his wings, dive and create turns.

The researchers found that the populations of Archeopteryx were very small. But scientists have not been able to thoroughly determine the way of life of these animals. The following version was put forward: Archeopteryx could live on low trees, descend from them and move perfectly along the ground. They descended to the ground in order to hunt very small prey, which they caught with the help of powerful jaws and claws.

Archeopteryx has a reptile body and tail, but with wings and plumage it looks more like a bird. With the discovery of Archeopteryx in the hands of paleontologists, the most convincing evidence of the origin of birds from reptiles has emerged. Only ten skeletons and a separate imprint of one feather of these prehistoric birds the size of a dove are known, and yet paleontologists managed to extract a mass useful information from these fossil remains. Since the first find of Archeopteryx was reported more than a hundred years ago, it has been the subject of heated controversy between supporters and opponents of Charles Darwin's teachings. In spite of everything, even in spite of the accusation of tampering with these findings, it has stood the test and served well in the cause of defending evolutionary theory from all attacks.

In 1985, the British astronomer Fred Hoyle claimed that a copy of Archeopteryx in the British Museum of Natural History was a fake. He claims the specimen was made by a con man who first applied a thin layer of binder mixed with powdered rock to the fossil skeleton of a small theropod dinosaur Compsognathus, and then made feather prints on it. In addition, Hoyle and his colleagues have suggested that other Archeopteryx specimens are either fake or mistaken for feather prints. As a result, Archeopteryx was soon considered the "Piltdown chicken" in England.

The wide response this statement received prompted the British Museum in 1987 to decide to hold a special exhibition in connection with the scientific examination of the specimen in its collection. The analysis showed that the material that stores the feather prints does not differ in composition and structure from the surrounding rock. Despite the quite modern appearance of the feathers of Archeopteryx, the prints do not bear any traces of forgery. Moreover, the pieces of rock enclosing the skeleton are very tightly adhered to each other, which would be impossible if they were bonded with cement.

Ironically, the features that Hoyle considered the most compelling evidence of a forgery, namely a combination of feathers modern look and bones that resemble those of Compsognathus are the most important arguments for paleontologists to understand how birds originated and how they developed the ability to fly. Archeopteryx combination anatomical features animals, belonging to two different classes, turns this oldest known bird into a textbook example of a transitional form between reptiles and modern birds.

Archeopteryx was opened as if by order of the Darwinists. In 1861, just two years after the publication of Darwin's book The Origin of Species by Natural Selection, a fossilized skeleton with feather prints was found in the limestone quarries of Solnhofen in Bavaria. The find fell into the hands of Karl Haberlein of Pappenheim, who later sold it to the British Museum.

This specimen, known as the London specimen, was not the first evidence of the existence of birds in the Upper Jurassic period, that is, 150 million years ago. A year before the London specimen was found, a stone with a feather imprint was picked up in the same quarry near Solnhofen. Prior to this, the earliest fossil remains of birds were attributed to the Tertiary period and dated to almost a hundred million years later than samples from the Solnhofen limestones.

In 1861, the paleontologist Hermann von Meyer, who worked at the Joint Museum of Natural History and the Senckenberg Research Institute in Frankfurt, confirmed that the found feather print is indeed a fossil and is very reminiscent of the feather of a modern bird. In the same message, he mentions a London copy: “In a lithographic stone, an almost completely preserved skeleton of an animal covered with feathers was found. It is believed that it differs in many ways from modern birds. I publish the results of the study of one feather and its exact representation. I believe that the most appropriate name for the newly found animal would be Archeopteryx lithographica. "

So the name of the bird from Solnhofen was introduced into scientific use: Archeopteryx lithographica. Literally translated, the word Archeopteryx means "ancient wing", and the definition of lithographica reminds us that the Ashnhofen limestone of the 19th century. was called a lithographic stone. True, the stone mined in the quarries of Solnhofen was too hard, dense and fine-grained and therefore not very suitable for use in printing. But it was precisely these properties that contributed to the preservation of such an incredibly clean and clear imprint of Archeopteryx feathers.

The exceptional preservation of the remains of Archeopteryx is also explained by the geological conditions of the formation of the Ashnhofen limestones. At the end of the Jurassic period, the territory of the southern part of the present mountain range of the Franconian Alb was a tropical lagoon, dissected into separate bodies of water by underwater reefs. To the north of the lagoon lay the land that is now occupied by central Germany. To the south of it was the ancient Tethys Sea.

This area was not at all like the paradise of the southern seas: the water in the lagoon was too salty and almost did not contain oxygen, and therefore did not really attract the living organisms that existed at that time. Occasional storms caused floods, the water inundated the reefs that bound the lagoon to the south, and brought many animals and plants into the water bodies. They quickly perished in the water of the lagoon, sank to the bottom and were covered with a layer of silt containing a large amount of lime.

The lagoon also served as a burial place for animals and plants from the land areas lying to the north of it. This land was home to a wide variety of life forms: conifers, ferns, ginkgo trees, insects, dinosaurs and Archeopteryx. Tropical storms carried flying animals out to sea, and they could fall into the lagoon. Plants and corpses of animals were carried here by rivers. And since there were practically no carrion and microorganisms in the salty water of the lagoon, almost intact dead animals and plants were buried in the calcareous bottom sediments.

There are currently ten known Archeopteryx skeletons. All of them are found in the Solnhofen limestones that formed in the Upper Jurassic. These findings represent the oldest known bird fossils. True, Sankar Chatterjee of the Texas Tech University in Lubbock discovered parts of skeletal fossils in older Triassic sediments in Texas, which he considers to be the remains of a bird he named Protoavis. However, these remains are, in fact, scattered fragments, and their belonging to birds needs to be proven. The finds from Solnhofen are still important for understanding the behavior and structure of Archeopteryx, as well as the origin of birds in general.

The London specimen is an almost complete skeleton of Archeopteryx. The skull is the worst preserved, represented by separate fragments, among which are the bones surrounding the brain and parts of the jaw bones that bear the teeth. In addition to clear signs of feathering on the wings and tail, the remains of Archeopteryx bear other features characteristic of birds. There is, for example, a fork (or arch), which appeared as a result of fusion of the clavicles. Several years ago it was believed that only birds have a fork. However, more recently, it was also found in some dinosaurs that lived in the Cretaceous period.

The next specimen was found in the fall of 1876 in a quarry near Eichstätt and some time later sold to Ernst Haberlein, the son of the very man who drew the attention of paleontologists to the first find. At first, E. Haberlein believed that the skeleton belonged to a flying reptile. It was only after removing the top layer of the rock from the sample that he found well-preserved feather prints, which made him change his original opinion. In the end, the copy was acquired by the Natural History Museum of the Humboldt University in Berlin, where it has been located since 1881.

This copy is known under the name of Berlin and has survived much better than the London one. The almost unresolved skeleton looks very natural. This suggests that during burial at the bottom of the Solnhofen Lagoon, the animal did not undergo decomposition at all. Its skull and teeth were much the same as that of reptiles. The neck is bent far back, pulled by the ligaments after the muscles relax. This is typical of dead birds, although fossils of flying dinosaurs and some small, long-necked dinosaurs, such as Compsognathus, have been found in the same position.

The Berlin specimen has well-preserved flight feather prints. The three "fingers" of the wing (anatomists usually combine them into a hand) were mobile and carried sharp, strongly curved claws. The fingers of modern birds are shorter, partially accrete and do not have such claws.

The Berlin specimen has plumage on both sides of the long, lizard-like tail of the Berlin specimen. In other words, the tail bears two rows of feathers that are symmetrically arranged in a horizontal plane. Feather prints convey the smallest details, giving a complete picture of their structure, right down to the well-distinguishable interlocking barbs.

It took more than a hundred years after the Berlin specimen was found before the next specimen was found. In 1956, the remains of another winged creature were found in a quarry near the site of the London specimen. After studying them, paleontologist Flornan Geller of the University of Erlangen concluded that they belong to the same animal as the London specimen, i.e., Archeopteryx lithographica. This sample is kept by a private person, but until 1974 was exhibited at the Maxberg Museum, near Solnhofen. Hence its name - Maxberg copy.

The animal, preserved in the form of the Maxberg specimen, after death, apparently, swam in the water for a long time, since it lacks a head and tail. They must have separated from the body prior to sinking into the sediments. The legs and wings are also mixed from their natural position, but judging by the orientation of the feathers, they were held in place by tendons.

Another specimen of Archeopteryx was born after more than a hundred years lay unidentified in the storerooms of the Teyler Museum in the Dutch city of Haarlem. It was "mined" in the quarry in 1855, that is, before the London copy. But in 1857 it was mistakenly decided that this fossil skeleton belongs. It was only in 1970 that John Ostrom of Yale University identified it as the skeleton of Archeopteryx. The specimen is very poorly preserved: only fragments of the bones of the left wing, pelvis and hind limbs remained. However, the claws on the wings and legs are very clearly visible.

The classification of the other specimen was also erroneous at the beginning. It was found in the Eichstätt area in 1951, five years before the Maxberg specimen was found. The size of this skeleton is smaller than that of all the others, but it is almost completely preserved. At first, it was mistaken for the remains of a small reptile like Compsognathus, which had reached the size of a chicken. Only in 1970, Franz Mayr of the University of Eichstätt, examining the fossil in oblique beams of light, discovered faint imprints of the wing and tail. This allowed the find to be identified as the remains of Archeopteryx.

The Eichstätt specimen has a much better preserved skull than all the others. The most recent CT scans of the skull show very well that the articulation of the square bone with the skull in Archeopteryx was much the same as in modern birds. In the Eichstätt specimen, just like in the Berlin one, the neck is bent far back. Taking into account the good preservation of the skeletons and their position, it can be assumed that the death of both birds occurred under similar circumstances.

It is quite obvious that the Archeopteryx of their Eichstätt did not die of old age. Its skeleton is small and most likely belongs to a young individual. The metatarsal bones in the lower limbs do not show any signs of fusion, which are clearly visible, for example, in the larger Maxberg specimen. In addition, the well-preserved skeleton lacks a fork. It seems very plausible to suppose that by the time of the death of Archeopteryx, the fork still consisted of cartilaginous tissue and did not have time to ossify, and therefore did not survive in a fossil state.

Long legs are another distinctive feature of the small Archeopteryx from Eichstätt. This indicates a more rapid development of the hind limbs in comparison with the wings and some other parts of the body. Perhaps young animals walked much more often than they flew, and the ability to fly developed at a later age.

Another specimen of Archeopteryx was discovered in 1987 after Gunther Viol, curator of the Jurassic Museum in Eichstätt, found a prehistoric bird in a fossil collection belonging to the former mayor of Solnhofen, Friedrich Müller. This specimen has no feather prints and most of its skull has been lost. Due to its long, strong legs and long tail, the skeleton has long been mistakenly thought to belong to Compsognothus. Now this copy is the property of the village of Solnhofen and is exhibited in the Museum of Mayor Müller.

All the surviving body parts of the Solnhofen specimen remained in their places, their natural articulation was not disturbed. When illuminated from the side of the specimen at an acute angle, faint imprints of the curved rods of the largest feathers can be seen on the left wing. The same prints are located along the edge of the wing. There are no traces of feathering of the right wing and tail, which can be explained by the position of the skeleton. Apparently, when diving into the Solnhofen lagoon, the corpse lay on the bottom with its left side and the left wing sank deep into a thick layer of silt, which ensured its good preservation. Feathers of other parts of the body that remained on the surface of the bottom soil could be carried away by the current.

The most striking feature of the Solnhofen specimen is its size. The wings are 10% longer than the London specimen, the largest previously known, and 50% longer than the smaller specimen from Eichstätt. This Archeopteryx was no less than a chicken.

Before wondering what the significance of finding these six specimens (and the individual featherprint) means, you should be sure. that they all really represent the remains of animals of the same species. Their classification has always served as the basis for the most controversial judgments. Over the years, different specimens have been given a wide variety of names, countless attempts have been made to classify animals as different biological species and even genera.

From the point of view of a paleontologist, the biological definition of a species as an aggregate of actually or potentially interbreeding populations does not make much sense, since this criterion is unsuitable for characterizing long-extinct animals. When determining the species belonging of this or that specimen, the paleontologist most often has data other than the morphology of the skeleton. With such incomplete information, he must very clearly distinguish between the characteristics inherent in this species, and individual characteristics structures due to gender, age and other properties of the animal. Therefore, * the species identification established on the basis of paleontological analysis does not always coincide with the results of its determination based on biological characteristics.

The difficulty in classifying Archeopteryx is partly due to the impossibility of judging from the available bone remains about the nature of their growth, which could occur either as in reptiles or as in birds. The growth of reptiles continues throughout life, although it slows down with age. Birds, on the other hand, very quickly reach the size of an adult. The centers of growth in reptiles are located in the diaphysis of the tubular bones, while in young birds they are located in the thickened cartilaginous ends of the bones - the epiphyses. At the final stage of bird growth, the cartilaginous tissue of the epiphyses is ossified, and gradually dissolving scars remain in its place.

None of the available specimens of Archeopteryx have such scars on the tubular bones. If the growth of these animals proceeded in the same way as in birds, then the surviving remains should really be considered belonging different types animals. If Archeopteryx grew like reptiles (which is very likely, given the predominance in their skeleton of features characteristic of reptiles), then these remains undoubtedly belong to the same species, although the individuals representing it differed in sex and age. The latest research by Marilyn Hawke and Richard Strauss from the University of Piece. Arizona and Jacques Gaultier confirm that all Archeopteryx specimens are of the same species, but represent individuals of different ages.

We still know very little about Archeopteryx. It is not known, for example, when the found individuals lived: perhaps the time of their existence is separated by hundreds or thousands of years. It is also impossible to answer the question of what gender they were. Therefore, it is more reasonable to attribute all fossil remains to one species: Archeopteryx lithographica.

Outwardly, Archeopteryx looked very much like a bird. Therefore, the question naturally arises whether these animals could fly. Recall that none of the specimens found has a sternum or sternum, even if we are talking about the largest, apparently adult, individual from Solnhofen. There is no doubt that Archeopteryx did not develop a bony or ossified sternum at all, without which modern birds simply could not fly.

The sternum of birds is a wide, arch-shaped bone and in many species reaches the pelvic region, forming a kind of bowl that interferes and protects the internal organs during flight. In the middle of the sternum, there is a ridge to which the pectoral muscles are attached. No living creature can compare with birds in terms of the ratio of the size of the pectoral muscles to the rest of the body. It is these huge muscles that provide the wings of a flying bird.

We have no evidence that the pectoral muscles of Archeopteryx were developed to the same extent as in birds. Instead of the sternum, these animals, like their lizard-like ancestors, had abdominal ribs. They are thin, fish-like bones that span the abdomen and are not attached to the main skeleton. They are also found in modern lizards and crocodiles and, apparently, quite often found in primitive reptiles and amphibians. It is possible that in Archeopteryx, the abdominal ribs served to protect the abdominal cavity and support the internal organs. Of course, the pectoral muscles could not be attached to them.

For all that, Archeopteryx, like birds, had a fork. Since in birds some pectoral muscles are attached to it, it is logical to assume that in Archeopteryx, there was a small area on the bow that served for the same purpose. Nevertheless, the flying qualities of these animals were more than modest.

There is other evidence of a limited flight ability in prehistoric birds. In modern birds, the lungs are associated with air sacs in other parts of the body, even in the bones, thanks, in particular, to small holes in the upper ends of the humerus. These air-filled cavities improve the breathing of the birds and allow them to meet the urgent oxygen requirements that arise during flight. There are no holes for air sacs in the bones of Archeopteryx. It is doubtful that his lungs were designed in the same way as those of birds.

Unlike birds, the Archeopteryx hand consisted of non-fused bones and, therefore, could not serve as a supporting element of the wing. The fingers could move independently of each other and ended in strong, pointed claws. The largest feathers of the hand extended from the middle finger, while the smaller feathers were attached to the ulna, the main element of the forearm. The ulna of Archeopteryx is smooth, in contrast to the same bones of birds, covered with small tubercles, to which feathers are firmly attached with the help of ligaments. Thus, the large feathers of Archeopteryx did not appear to have been associated with bones.

The weak development of the pectoral muscles, the structure of the lungs characteristic of reptiles, and the absence of strong attachment of the flight feathers - all this suggests that the ability of Archeopteryx to fly was rather poorly developed.

And yet these animals could fly! Otherwise, they would not have such a powerful plumage. No other vertebrate animals besides birds have real feathers. And it was feathers that played a decisive role in the development of the ability to fly.

According to modern concepts, plumage arose from the scales of reptiles. Did feathers or similar formations protect warm-blooded dinosaurs from the cold? Or did they protect cold-blooded reptiles from heat and sunlight? Perhaps the feathered limbs were used to attract sexual partners or in the fight against rivals during the mating season? Or served as a "net" for the extraction of insects? These and other assumptions have been expressed more than once, but have remained unanswered.

Only one thing is clear: Archeopteryx is a very big step forward in the evolution of flight. Its feathers have an asymmetrical aerodynamic shape typical of birds. Such an analogy once again confirms that feathers served for flight, and their rather complex structure makes one think that the hypothetical ancestor of Archeopteryx also had feathers, although they may not have been adapted for such complex actions yet.

Archeopteryx did not fly long distances, but was apparently capable of heavy flight from place to place with sharp flaps of wings, and, moreover, was good at running. The structure of the pelvis and lower limbs of this prehistoric bird testifies to the fact that it was completely free to move on the ground. Its three-rayed pelvis closely resembles the similar formation of dinosaurs lizard-like, especially bipedal theropods of the Compsognathus type. Therefore, one should think that the muscles of the pelvis and legs of Archeopteryx were also similar to the muscles of lizard-like dinosaurs.

Archeopteryx must have stood just as well on its hind legs as Compsognathus and others. However, his posture was different from that of modern birds, whose body, like a swing, is suspended from the pelvis with the femurs in an almost horizontal position. Like Compsognathus, the body of Archeopteryx did not tilt forward because it was balanced by the weight of the tail, which was almost as long as the body.

The tail bent freely near the base, but towards the end it largely lost its flexibility due to the bony outgrowths of 23 caudal vertebrae, which were also found in some bipedal dinosaurs and flying dinosaurs with a long tail that lived in the Triassic and Jurassic periods. The rigid tail design allowed the animals to maintain balance during sudden changes in direction of movement, be it running or flying. In addition, the plumage of the tail formed an aerodynamic horizontal surface, which served to preserve desired position body.

The tail vertebrae of modern birds have decreased in size and merged into a pygostyle, one of the few formations found only in birds. The decrease in the length of the caudal vertebrae in birds, which replaced Archeopteryx, should have been accompanied by a gradual displacement of the center of gravity towards the front of the body. In order to partially compensate for this shift, there was an increase in the muscles of the pelvic girdle, accompanied by a corresponding increase in the surface of the pelvic bone, to which this musculature was attached. In the process of changing the structure of the pelvis, the two fused pubic bones separated and turned out to be turned back. As a result, the entire load of the internal organs fell on the sternum, which required its further development.

The legs of Archeopteryx are very well adapted for running, and in their structure they occupy an intermediate position between the hind limbs of reptiles and modern birds. In the latter, the bones of the metatarsus have grown together into one bone, while in reptiles they are connected movably. Wilhelm Stürmer, a physicist and paleontologist at Siemens in Erlangen, examined a Maxberg specimen of Archeopteryx in X-rays and found partial fusion of the metatarsal bones. In the largest available specimen, the Solnhofen, these bones have grown even more. These observations indicate that the bones of the metatarsus of Archeopteryx ossified and fused with age.

In general, the structure of the hind limbs of Archeopteryx and its ancestors from the theropod group is very similar to the structure of the legs of modern birds. They had three long fingers and one short one, facing back. This short toe was armed with a sharp curved claw, thanks to which the prehistoric bird could grab various objects and sit on tree branches.

From all that has been said, it follows that the development of the ability to fly was accompanied by a restructuring not only of the organs that directly determine flight qualities, but also corresponding changes in the entire skeleton and even physiological characteristics animals.

Currently, there are two main, but contradictory models of flight evolution. According to the so-called "arboreal" model, flapping flight evolved in animals that climbed trees and jumped from their branches down to the ground. Adherents of another hypothesis believe that the origin of flight is associated with animals running on two legs, which, while running or jumping (for example, in pursuit of insects), helped themselves with their front limbs in order to increase the length of the jumps. As the elements of the wing developed, the jumps became longer and higher, until finally the animals took to the air, striking their wings.

The second hypothesis is supported by the purely mechanical structural features of Archeopteryx, which serve as adaptations for movement on the ground. However, the energy costs with this method of movement, and even with the help of wings, would be difficult to replace, especially in the early stages of flight. In addition, in order to rise into the air, it is necessary to overcome gravity, while planning from the trees down, on the contrary, allows the use of gravity and therefore is energetically more beneficial.

The “tree” model assumes that Archeopteryx and its ancestors climbed trees. Could the presence of claws in these animals warrant such an assumption? Archeopteryx's claws were curved in the shape of a sharp sickle, had a cutting edge on the inside, and thickened on the outside. The same claws are found in bats, squirrels and woodpeckers, that is, in all animals that climb tree trunks and cling to the bark. The claws birds of prey and mammals that run on the ground are structured very differently. Now birds climb trees exclusively with the help of the claws of their feet. Archeopteryx also used claw-armed fingers, especially the first, the most flexible of them, acting as an anchor or a hook. The tail created additional support.

The model, which combines the features of both the above-described models, can be called “arbokursorny” (from Latin arboreus - “arboreal” ucursorius - “running”). It builds in part on ideas expressed by Walter Bock of Columbia University.

According to this theory, the ancestors of Archeopteryx were small, possibly walking on two legs, reptiles that moved to trees in the Upper Triassic and Lower Jurassic times, about 200 million years ago. The forests served as a shelter, a breeding ground for these animals, where they made nests. Perhaps it was easier to get food in them. The onset of arboreal life in these precursors of birds probably coincided with the development of warm-bloodedness and was accompanied by the formation of feather-like outgrowths, which served as an insulating cover that ensured the maintenance of a constant high temperature body. Life in trees was also supposed to contribute to the emergence of three-dimensional vision and the ability to navigate in three-dimensional space. Both of these qualities created additional prerequisites for the formation of flight skills.

Large feathers, due to air resistance, reduced the rate of descent and softened the landing of primitive birds when they jump to the ground. Such a delayed form of flight could give rise to another form of flight - gliding, and the ability to maintain a straight flight was probably provided by the flaps of the wings.

With Archeopteryx's legs adapted for running, ground locomotion remained an important mode of movement for these prehistoric birds and their distant ancestors. To glide between trees and sit on branches required perfect flight control and good coordination. It is obvious that a simple, like a parachute, landing was given to primitive birds much easier than a tree landing that required more complex movements. Having reached the ground, these animals shuffled to the next tree and climbed it in search of insects, shelter or a place to build a nest.

Was Archeopteryx the ancestor of all birds after it? What is the general value for understanding the evolution of this class of animals are fossils dating back to the later, Cretaceous period? More or less fully preserved skeletons of birds were found only in the Upper Cretaceous deposits, formed about 85 million years ago. These birds had teeth and were to a certain extent adapted to the aquatic lifestyle. They could, in particular, dive. It is hardly possible to consider such highly specialized animals as direct descendants of Archeopteryx. In this regard, the opinion is often expressed that Archeopteryx represents a dead-end branch of bird evolution.

Fortunately, fossilized remains of birds from the Early Cretaceous era, about 125 million years ago, have also been found. They can be considered a transitional form from Archeopteryx to modern birds. For example, the skeleton of a small bird, discovered in 1984 in the limestone deposits of Las Ojas in east-central Spain, is characterized by a combination of ancestral and modern forms. The pelvis and hind limbs are more reminiscent of the bones of reptiles than of today's birds. At the same time, the shoulder blades and fork are much larger than those of Archeopteryx, and are similar to the same bird bones. But the most interesting is the structure of the pigostyle, which consists of 15 accrete vertebrae. It is longer than the pygostyle of modern birds, formed by 4-10 accrete vertebrae, but shorter than the tail of Archeopteryx with its 23 vertebrae.

The bird from Las Oyas, like Archeopteryx, serves as a good illustration of the primary development of mechanical adaptations necessary for flight in the early stages of bird evolution. Now we cannot say whether Archeopteryx was the direct ancestor of the bird from Las Oyas and all other birds. In the end, the answer to this question is not so fundamental. It is much more important to remember that several currently known Archeopteryx skeletons and a single feather print provide clues to the origin of birds. Consider the thought of Adolf Portmann, a zoologist at the University of Basel, which he expressed about fossil remains back in 1957: "These are documents without which the very idea of ​​evolution would not look so convincing."