Strange fossils discovered in the middle of the twentieth century. in the US state of Illinois, became the beginning of one of the most interesting mysteries of paleontology. In honor of Frey, who found the first sample. Paleontological mysteries Mysteries of paleontology

New paleontological finds are changing the perception of pterosaurs - and the most bizarre animals ever to fly above the earth.

Pterosaurus and pterodactyl are two names for strange flying creatures; the first of them in Greek means "wing-lizard", the second - "flying finger".
For the first time the remains of such an animal were found in the XVIII century. Since then, scientists have described more than 200 species of winged lizards, but the philistine ideas about these dragons, which reigned in the sky of the Mesozoic era for more than 160 million years, remain the same.
We invariably imagine them as clumsy but very dangerous flying reptiles with long beaks and leathery wings, pacing on their hind legs like penguins.

Take, for example, the 1966 film A Million Years B.C., in which a shrieking purple pterosaur carries the character Raquel Welch to her nest to feed her cubs (spoiler alert: the bikini-clad beauty managed to escape). Has anything changed in 50 years? Not at all: in Jurassic World, filmed in 2015, pterosaurs still carry people more than their own weight into the sky. (Just in case, let's clarify: the last pterosaurs died out 66 million years ago, that is, a whole eternity before people appeared on Earth.)

A huge number of recent paleontological finds allows us to know that pterosaurs came in a wide variety of appearance and size, and their behavior also varied greatly. Hundreds of species of pterosaurs lived simultaneously, occupying different ecological niches, like today's birds. Among them were giant monsters, such as quetzalcoatl ( Quetzalcoatlus northropi), one of the largest flying creatures known today: standing on all fours, he could argue with the growth of a giraffe, and reached 10.5 meters in a wingspan. But there were also pterosaurs the size of sparrows, perched on branches in ancient forests, most likely catching insects.

One of the most curious finds is the fossilized eggs of a pterosaur. By scanning the best-preserved ones, the scientists saw the embryos under the shell and were able to learn about how they developed. One egg was even found in the oviduct of a female Darwinopterus that lived in China, and next to it another, which apparently squeezed out under the weight of volcanic ash that covered the animal. Mrs. T (as this female was named) was the first pterosaur whose gender was precisely determined. She did not have a crest on her skull. Perhaps such outgrowths adorned only the heads of males, as they adorn the males of some modern bird species - nature gave them a large, brightly colored crest to attract individuals of the opposite sex.

After all these finds, pterosaurs seem to have become closer to us, but scientists are still not enough. And so, on the way to Big Bend National Park in southwest Texas, paleontologist Dave Martill of the University of Portsmouth shares his work plans with me: first, meet and admire a rattlesnake; secondly, to find a whole skull of quetzalcoatl. The chances of fulfilling the first item of the program are immeasurably higher.

The most important thing for a pterosaur specialist is to be an optimist. To imagine that on such and such a day you will go there and find at least something related to them is like buying a lottery ticket and immediately start planning what you will spend the winnings on. Pterosaur fossils are extremely rare because their bones were hollow and thin. As for the quetzalcoatl, we know about it thanks to only a few fragments found in Big Bend Park in the 1970s.

The hollow, ultra-light bones of pterosaurs were good for flight, but are rarely as intact as these anhanguera remains. In most cases, they are squeezed, "as if a skating rink drove over them."

Martill and his colleague Nizar Ibrahim spent three days looking for fossilized bones in the beds of dried-up rivers on the lands of the park. They went up and down the Pterodactyl Ridge (what a promising name!), now and then checking the maps compiled by the discoverer of this lizard. They delved into all the nuances of geological strata (“Look at these manifestations of Milankovitch cycles!” Martill exclaimed, meaning that periodic changes in the shape of the Earth’s orbit and its axial tilt, as established by the Serbian astronomer Milutin Milankovitch at the beginning of the 20th century, affect the climate planets, and this is reflected in the cyclic structure of sedimentary deposits). Climbing onto a sandstone ridge, from which it seemed impossible to get off, Martill only dropped: “Where ours did not disappear!”, Jumped down and remained safe and sound.

However, the researchers did not happen to meet a rattlesnake, nor even find a fragment of a pterosaur bone. As a consolation, they came across the femur of a giant dinosaur, apparently a sauropod. But dinosaurs don't interest them.

Leaving the national park, paleontologists are developing a plan for new searches for quetzalcoatl - they really want to learn more about this amazing lizard, in which everything is unusual: size, appearance, and behavior - this can be judged by the few fossils left from it.

INSTITUTE OF VERTEBRATE PALEONTOLOGY AND PALEOANTHROPOLOGY, BEIJING Few traces of hairs or down have been preserved in some areas of the Zheholopter fossil from China. (For the first time, such integumentary structures were discovered by Soviet paleontologists in a Jurassic pterosaur.)

Ideas about pterosaurs have changed a lot - even in terms of their appearance and behavior. This is partly due to the fact that, until very recently, scientists had to base their conclusions on an extremely small number of samples.

Pterosaurs differed, frankly, in a very strange anatomy. It may seem that they were ill-adapted to life on the ground and in the air. It was once even thought that the wing-lizards crawled on their belly, or imagined them walking on their hind legs with long forelimbs stretched forward, like a zombie, and dragging behind, like a cloak, folded wings. Later, fossil tracks established that pterosaurs moved on four limbs, but there was still no clarity on exactly how and where they put their wings. And their flying abilities were so doubted that they were considered incapable of getting off the ground, except by throwing themselves down a cliff.

"It's quite common for individuals to have heads and necks three or four times as long as their bodies," says biophysicist Michael Habib of the Los Angeles County Museum of Natural History. Even scientifically trained artists often make mistakes when depicting them. “They take a bird as a model, just add membranous wings and a crest to it,” says Michael. “However, the proportions of the body in pterosaurs were not at all avian.”

Habib set out to redefine conventional wisdom about pterosaur biomechanics using, firstly, a mathematical approach and, secondly, a practical knowledge of vertebrate anatomy, which he acquired in another job, namely in the laboratory of the University of Southern California School of Medicine. Like most scientists, Michael believes that the first pterosaurs, which appeared about 230 million years ago, evolved from light, slender reptiles well adapted for running and jumping. The ability to jump - to grab a flying insect or dodge the teeth of a predator - has evolved into the ability, in Habib's words, to "jump and hover in the air."

At first, pterosaurs probably only hovered, and then, tens of millions of years before birds (and even more so before bats), they became the first vertebrates to master flapping flight.

Using the equations used in aeronautical engineering, Habib and his colleagues disproved the cliff jumping hypothesis. In addition, they proved that if pterosaurs took off from a vertical position, standing on their hind legs, then the femurs of large species would break from overload. Taking off from four limbs is more practical.

“You need to jump up, leaning on your forelimbs, like a high jumper on his pole,” Khabib explains. To take off from the water, pterosaurs used wings in the manner of oars in rowing: they pushed off the surface. And, again, like rowers, they had large, developed shoulders, which were often paired with startlingly small feet to minimize drag in flight.

The wing of a pterosaur was a membrane stretched from shoulder to ankle; but stretched her extremely long flying (fourth) finger, forming the leading edge of the wing. Samples from Brazil and Germany show that the membrane was riddled with fine muscles and blood vessels. Additional rigidity of the partition was given by the protein strands that “pierced” it. Today, scientists believe that pterosaurs could slightly change the profile of the wings depending on the conditions of flight, contracting muscles or turning the ankles in or out.

Changing the angle of the ossified tendon at the wrist, the pteroid, may have served the same purpose as reversing the slats on large modern aircraft—increasing lift at low speeds.

In addition, more muscles and a higher proportion of body mass were involved in flight in pterosaurs than in birds. And in their brain, like in birds (and even better), the frontal and visual lobes, the cerebellum and the labyrinth were developed: such a brain could quickly respond to changes in the situation in flight and transmit signals to numerous muscles that regulated the tension of the membrane.

Thanks to the work of Habib and his colleagues, pterosaurs are no longer a winged misunderstanding, but skillful aviators. Many species appear to have been adapted for slow but very long flight over long distances; they could hover over the ocean using weak, warm updrafts (thermals). There were also species that Khabib calls superfliers: for example, in a nyctosaurus (Nyctosaurus), similar to an albatross, whose wingspan reached almost three meters, gliding qualities, especially the distance it flew for each meter of descent, were quite comparable to the characteristics modern sport glider.

“Okay, everything is clear with the wings,” one paleontologist began after Khabib’s lecture. “But what about the heads?” In Quetzalcoatl, for example, the skull could be three meters long, while the body is less than a meter. And in a nyctosaurus, a long “mast” protruded from a huge skull, to which, probably, a crest was attached.

Answering the question, Michael spoke about the brain of pterosaurs, the mass of which, like that of birds, only slightly weighed down the huge head, spoke about the bones, which were hollow, like those of birds, and even lighter. The thickness of the bone walls sometimes did not exceed a millimeter, despite the fact that the bone tissue was formed by numerous crossed layers, which gave strength to the bones (like in multilayer plywood). And from the inside, the cavities were crossed by partitions for greater rigidity. All this allowed pterosaurs to achieve large body sizes without a significant increase in mass.

The crested skulls and gaping mouths were so huge that Habib, looking at them, developed the “Dire Gray Wolf Hypothesis”: “If you have a big mouth, then you can swallow more. And the protruding crest could attract females.” Well, going back to that paleontologist's question, pterosaurs, according to Michael, were "huge flying killer heads."

Junchang Lu, one of China's leading paleontologists, greets guests on a busy street in the center of Jinzhou, a major trading city in the country's northeast, and guides them through a dimly lit hallway of what appears to be an ordinary office building. This is actually the Jinzhou Paleontological Museum. Its director opens the door of a small pantry without windows, and the visitors see what would be the main attraction for visitors in any other museum: all the shelves and almost the entire floor are occupied by specimens with amazingly complete, in all the smallest details, the remains of feathered dinosaurs, ancient birds and, of course, pterosaurs.

On a large, almost shoulder-length stone slab, leaning against the wall opposite the door, a large, terrible pterosaur with a wingspan of four meters and tiny chicken hind legs - Zhenyuanopterus (Zhenyuanopterus) is visible. Its elongated head is turned sideways and seems to consist of only jaws, and the teeth become longer and more overlapping as they approach the beginning of the mouth. “This is to make it easier to fish while floating on the surface of the water,” Lu explains. Zhenyuanopter is just one of three dozen species of pterosaurs he has described since 2001 (many are still on shelves waiting to be studied).

NATIONAL MUSEUM OF NATURE AND SCIENCE, TOKYO The skull of the fish-eating anhanguera has been preserved in its natural position - to the delight of paleontologists.

The Jinzhou Museum is one of ten such paleontological museums dotted around Liaoning Province, which is a veritable treasure trove of pterosaur fossils and one of the areas where the finds have been made that have put China at the forefront of paleontology in recent times.

In addition, Liaoning is the main arena of rivalry, and outsiders compare what is happening here, not quite, however, justifiably, with the “bone wars” waged against each other in the 19th century by the pioneers of American paleontology, Othniel Charles Marsh and Edward Drinker Cope.

The sides of this rivalry are Lu, representing the Chinese Academy of Geological Sciences, and Shaolin Wang, whose office is crowded with fossils at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. These pundits, like Marsh and Cope, worked together early in their careers before going their separate ways, and since then they have treated each other with hostility, which, however, is not advertised. “Two tigers cannot live on the same mountain,” their colleague Shunxing Jiang chuckles.

In the decade and a half that has passed since then, Lu and Wang have more than once outstripped each other in the number of discoveries, and together they described more than 50 new species of pterosaurs - almost a quarter of everything that is known today. However, some of these new species will eventually be recognized as synonyms of the former, as is often the case in paleontology. However, the rival parties will have to make even more discoveries in the future. “They would have to work for ten years all day long to describe everything that they have already dug up,” one of the guests remarks with envy. Hearing this, Lü raises his eyebrows in surprise, "I think ten years won't be enough."

The success of Chinese scientists is explained not only by competition, but also by the fact that they were in the right place at the right time. China, along with Germany, Brazil, the United States and England, is one of the few countries in the world where 90 percent of all pterosaur fossils have been found. This happened not because pterosaurs lived only in the territories where these countries are now located - fragments of their skeletons are found almost everywhere. It's just that their remains are more fully preserved here.

This exclusivity is evident in the example of Liaoning Province. At the beginning of the Cretaceous period, Lu says, a very diverse community of organisms developed in the local forests and shallow freshwater lakes - dinosaurs, the first birds, many pterosaurs and insects. Due to the fact that volcanoes erupted from time to time in the neighborhood, many animals died under the ash and fell to the muddy bottom of the lakes. The victims of such catastrophes were buried very quickly, sometimes even without oxygen access to the remains, their tissues mineralized faster than they had time to decompose, and therefore survived. Paleontologists call such locations Lagerstätte (Lagerstätte is German for "deposit"). And all the same, such finds still have to be dissected for months - cleaned of rock so that all their features can be seen, including, of course, with the help of all kinds of powerful microscopes.

It's only in places like the Beipiao Pterosaur Museum or the recent wing-lizard exhibit at the Beijing Museum of Natural History that you begin to perceive fossils differently—as part of a former great diversity.

Take, for example, the Jeholopterus, a pterosaur with a wide, frog-like mouth that scientists believe preyed on dragonflies and other insects. Here is the Ikrandraco, named after the winged creatures from Avatar, which probably flew low above the surface of the water and fished with a keel-like keel on its lower jaw. Here is a dzhungaripter (Dsungaripterus) found in northern China with a thin beak bent upwards, with which he hooked mollusks and other invertebrates in order to then crush their shells and shells with tuberculate teeth.

And all this disappeared at the end of the Cretaceous period, 66 million years ago. What turned out to be wrong with the pterosaurs, which eventually became completely extinct? Maybe the animals they hunted disappeared? Or, in the course of evolution, did they reach such gigantic proportions that they could not survive a global catastrophe, like the fall of an asteroid, while small birds survived?

However, when you look at their perfectly preserved remains in the museum, you don’t think about it - something amazing happens: it seems that these creatures are ready to free themselves from stone captivity and go in search of their missing fragments in order to soar above the earth again.

Click on the magnifying glass in the right corner of the picture to view it in its entirety.

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Since their discovery in Patagonia in 1891, Necrolestes have been a mystery.

An international team of researchers, including scientist John Wible of the Carnegie Museum of Natural History, has made an incredible discovery about Necrolestes patagonensis, whose name translates to "tomb raider" because of its underground lifestyle. This most talked about fossil mammal from South America has been a paleontological mystery for over 100 years.

Persistence in research, recent fossil discoveries, and comparative anatomy have helped researchers correctly place the 16-million-year-old strange Necrolestes, with its high-turned snout and large burrowing limbs, in the mammalian evolutionary tree. This discovery shifted the bottom of the evolutionary origin of fossils to 45 million years ago, proving that the mammal family survived the extinction event that ended the age of the dinosaurs. This fact is an example of the Lazarus effect, when it turns out that a group of organisms lived much longer than expected. The assignment of Necrolestes to their relatives in the fossil record answers one long-standing question, but raises new questions, reminding us that there is still much we do not know about the global consequences of the mass extinction 65 million years ago, a discovery that challenges the assumption that well-studied and documented phenomena that occurred in western North America have occurred throughout the world. A scientific article about the unraveling of the Necrolestes mystery will appear in the Proceedings of the National Academy of Sciences.

Paleontological mysteries

Since their discovery in Patagonia in 1891, Necrolestes have been a mystery. "Necrolestes is one of those animals whose photos, if they appeared in textbooks, would be accompanied by the caption: 'We don't know what it is,'" says co-author John Wible of the Carnegie Museum of Natural History, a mammologist and member of the scientific team that also includes researchers from Australia and Argentina. Weeble is known for his work on the origins and evolutionary relationships between three groups of modern mammals: placentals (viviparous mammals such as humans), marsupials (marsupial mammals such as opossums), and egg-laying mammals (such as platypuses).

The Miocene mammal Necrolestes patagonensis appeared in this world 16 million years ago in Patagonia, present-day Argentina. Necrolestes are now classified as one of the species thought to have become extinct shortly after the extinction of the large dinosaurs at the end of the Cretaceous. Photo from phys.org

Despite excellent preservation, the mysterious fossils move from one institution to another and from explorer to explorer, and the classification of Necrolestes changes with each new move. As recently as a few years ago, Necrolestes still could not be definitively assigned to the group of mammals. A CAT scan of the ear area in 2008 led to a hypothesis put forward by another research group that classified Necrolestes as a marsupial. This discovery intrigued Weebl, co-author of the work, and Guillermo Rugier of the University of Louisville, Kentucky. As a specialist in South American mammals, Rougière was not convinced that "marsupial" identification was accurate and set about his own attempts to classify the animals. “This project scared me a little, because we had to challenge an interpretation that had existed for 100 years,” admits Rougière.

In the process of preparing the fossils for further study, Rougière uncovered skull characteristics and anatomical features that had not previously been seen. Based on these newly discovered facts, the research team came to the conclusion that Necrolestes did not belong to either the marsupials or the placentals, to which it has always been attributed. Most likely, in fact, the Necrolestes belonged to a completely unexpected branch of the evolutionary tree, which was believed to have become extinct 45 million years before the appearance of the Necrolestes.

Mysterious anatomy

One of the conundrums of the Necrolestes was the impossibility of assigning their anatomical features to any one kind of classification. Given the body features in the form of a highly raised muzzle, a solid body structure and short, wide feet, researchers have always believed that they must be classified as burrowing mammals. Burrowing mammals have a broad humerus (upper arm bone) that is adapted for burrowing and tunneling. The humerus of Necrolestes is wider than that of any other burrowing mammal and indicates that Necrolestes are especially specialized in burrowing, perhaps even more so than any other known burrowing mammal, but this trait does not make the task of classification any easier. The simple triangular teeth of Necrolestes served it well for feeding on subterranean invertebrates. However, until recently, the features of the teeth were of little help in classifying Necrolestes, because their teeth are so simple that it is impossible to state their unambiguous resemblance to any other mammals.

The secret is revealed

In 2012, the extinct mammal Necrolestes, rediscovered to the world, became the key that unlocked the secret of the "diggers of the earth." Discovered in South America by co-author Rougière, Necrolestes belongs to the Meridiolestida, a little-known group of extinct mammals that lived in the late Cretaceous and early Paleocene (100 million years ago) in South America.

Evolutionary Consequences

The mass extinction that ended the age of the dinosaurs wiped out thousands of animal species. Among those who disappeared were the Meridiolestida, a group of mammals to which the Necrolestes belong, interrupting their evolutionary line, as scientists used to think. Until the final identification of Necrolestes, only one member of Meridiolestida was known to have survived extinction, and this species also became extinct soon after, at the beginning of the Tertiary period (65.8 million years ago). Therefore, Necrolestes is the only remaining representative of supposedly extinct groups. “This is the clearest example of the Lazarus effect,” Weebl comments. “Is it possible that a species has existed on Earth for so long without anyone knowing about it?”

Rougière says: “In some ways, Necrolestes are similar to modern platypuses, although they have nothing else in common other than common characteristics. There are few platypuses, they are found only in Australia and occupy a certain niche among modern mammals, just like Necrolestes were an isolated line living only in South America, and there were few representatives of their genus compared to a large number of marsupials.

Recently, paleontologists, using the latest technology, discovered a snake in sediments that are 95 million years old. Yes, not just a snake, but with ... hind legs. This discovery made it possible to establish the ancestor of snakes, as well as to find out how these reptiles lost their legs during evolution, which has so far been one of the mysteries of paleontology.

These fossils, which are 95 million years old, were found back in 2000 in the Lebanese village of Al Nammura. The remains belonged to the snake Eupodophis descouensi. This reptile reached 50 centimeters in length. The recovered remains were transferred to the Museum of Natural History (Paris) for further research.

And recently, a group of scientists led by Dr. Alexandra Usse, using X-rays, carried out layer-by-layer scanning of the sample and, based on its results, built a computer model of the object under study in a 3D format. It turned out that this snake had hind limbs, although very reduced.

The image quite clearly shows that the internal structure of the bones of the paws of ancient snakes largely resembles the structure of the legs of modern terrestrial lizards. True, thighs and shins Eupodophis descouensi very shortened, there are also ankle bones, but the foot and fingers are already missing. Moreover, the exhibit had only one leg free, and the second was hidden in stone, but an X-ray examination was able to show the scientists even her. Since both legs are arranged in the same way, we can safely assume that the absence of some parts of the limb is not the result of injury or deformity, but an indicator of the beginning of the reduction of the paws in snake ancestors.

"Discovery of the internal structure of the hind limbs Eupodophis allows you to explore the process of limb regression in the evolution of snakes. Currently, there are only three fossil snakes with preserved hind limbs and lost forelimbs. They belong to three different groups - these are Haasiophis,Pachyophis and Eupodophis. Other known fossil groups of snakes have no limbs. Nevertheless, based on their anatomical structure, it is believed that they still had limbs, but then disappeared.

Now we can even say how, most likely, such a reduction took place. These studies show that the loss of limbs by the ancestors of snakes is not the result of any anatomical changes in the structure of the bones, but most likely was associated with a reduction in the growth period. Due to some genetic changes, the paws did not have time to fully form in the embryonic period, so the snakes were born with a little “unfinished” legs, ”says the team leader, paleontologist Alexandra Usse.

By the way, this version is also confirmed by the studies of domestic embryologists. Not so long ago, studying the so-called Hox genes (these are the genes responsible for the formation of the body of the embryo in the early stages of development) of snakes and lizards, scientists found that the latter lack the Hox-12a gene, and also Hox-13a and Hox- 13b. It is known that these genes are responsible for the formation of the rear end of the body of reptiles, as well as for the appearance and development of the hind limbs. The resulting mutation, as a result of which one of the genes disappeared completely, apparently led to the fact that the hind legs ceased to develop normally, and the change in its two "neighbors" led to the complete disappearance of these limbs.

However, the question of the origin of snakes is still one of the most mysterious in paleontology. Scientists believe that these reptiles evolved about 150 million years ago from some group of lizards. It is still unclear what kind of group this was, as well as why the snakes became long and legless.

According to one point of view, the loss of limbs is associated with the transition to an aquatic lifestyle. In the water, paws are not needed, it is much more profitable to move there, bending the body in a snake-like manner. This version is confirmed by the fact that one of the ancient two-legged snakes, Pachyophis, was an aquatic animal.

The disadvantages of this version are the fact that among the primitive snakes there are no those who live exclusively in the water, such appear only among the advanced representatives of the group, for example, sea snakes ( Hydrophiinae). In addition, in the paleontological record, snakes are extremely rare in marine and freshwater sediments, which is rather strange, since the fauna in such burials is preserved several orders of magnitude better than in terrestrial ones, and they come across more often. Also against this version is also the fact that, apart from the absence of limbs, primitive snakes have no other adaptations for life in water.

According to another hypothesis, the ancestors of snakes were burrowing lizards that lost their limbs due to the fact that underground they do more harm than good. This version is confirmed by the fact that primitive snakes from the group of blind snakes ( Typhlopidae) are truly underground animals. The burrowing way of life, apparently, was also carried out by fossils Haasiophis and Eupodophis. It is also known that representatives of many groups of lizards, for example, skinks ( Scincidae), legless lizards ( Anniellidae), spindles ( Anguidae) or scalefoot ( Pygopodidae), during the transition to a burrowing lifestyle, they also lost limbs (at the same time, not a single case of loss of legs in aquatic lizards is known).

So, most likely, the ancestors of snakes really led a burrowing lifestyle. That is why they needed a long body (it is easier to squeeze through the ground). Also in connection with this, they gradually lost the outer openings of the ears (so that the earth would not clog), limbs and moving eyelids (there is no need for them underground, the eyes do not dry out in moist soil), and in return they acquired a transparent film formed from fused eyelids, protecting the eye (which is why it seems that the snake is hypnotizing us, its gaze is motionless).

For quite a long time, lizards from the group of monitor lizards were considered the ancestors of snakes ( Varanidae). These lizards, like snakes, have a long and movable tongue, a highly developed Jacobson's organ responsible for chemoreception, an additional movable articulation of the branches of the lower jaw, and also a structure of vertebrae similar to snakes. In addition, earless monitor lizards living in Indonesia ( Lanthanotidae), as their name implies, like snakes, lack external ear openings. However, the details of the structure of the skull in monitor lizards and snakes are very different, and in addition, molecular analysis of DNA shows that the two groups are very far from each other. Also against this version is also evidenced by the fact that among monitor lizards there are no (and, apparently, there never were) representatives leading a completely underground lifestyle.

But with another group of modern lizards called geckos ( Gekkonidae), snakes have much more common structural features (for who geckos are and what they are famous for, read the article "Secrets of night climbers"). In particular, the skulls of snakes and geckos are completely devoid of temporal arches (formed by the zygomatic bones) and have a movable articulation of the bones of the lower jaw. The eyelids of many geckos, as well as those of snakes, have grown together and formed a transparent outer shell of the eye. And, finally, among these lizards there are those who lead a burrowing lifestyle.

The most characteristic here are the representatives of the subfamily of the scalypods, which has already been mentioned above. Its representatives, living in Australia and New Guinea, have a snake-like elongated body and are extremely reminiscent of snakes in appearance. This similarity is also emphasized by the absence of the forelimbs and a significant reduction in the hind limbs, which usually look like short scaly outgrowths sometimes ending in claws, as well as the absence of external openings of the ears. Of course, it is unlikely that scalefoots were the direct ancestors of snakes, however, apparently, these are one of their closest relatives.

In addition, data from molecular studies also suggest that geckos are the closest relatives of snakes in terms of DNA structure.

According to these data, geckos and snakes separated from other scaly ones 180 million years ago, and the separation of these groups occurred a little later, about 150-165 million years ago. That is, approximately when, according to paleontologists, this group arose. So that's where it all comes together.

So, a new research methodology has helped scientists fill a gap in the history of reptiles and solve one of the most intriguing mysteries of evolution. It should be noted that paleontologists generally place great hopes on this technique. It allows you to get images with a resolution of a few microns - a thousand times less than a hospital tomograph.

The dramatic increase in biodiversity that occurred during the Cambrian period was prepared for a long time by molecular evolution, which eventually led to the Cambrian explosion of species diversity.

Trilobite is one of the ancient arthropods, whose appearance fell on the Cambrian period (photo by mattheaton).

In biology, there is a well-known paradox of the Cambrian explosion. Its essence is that from some point life on earth begins to demonstrate an enormous variety of forms, traces of which can be found in prehistoric fossils. This moment happened in the Cambrian period - but before that, no signs of future life forms could be found. Revolutionary leaps in nature are relatively rare, and if we talk about a planetary scale, they are completely incredible. Meanwhile, one gets the feeling that the organisms acquired at once, as if at a mass sale, an incredible number of new features and began to quickly disperse into systematic groups.

Of course, one can assume divine intervention or that some aliens have shaken out a bag of new species onto Earth. Scientists, however, did not stop trying to find at least some scientific explanation for the paleontological mystery. Charles Darwin thought about the problem of the sudden "emergence" of new fossil species - and came to the conclusion that in such cases, archaeologists and paleontologists need to "dig better" in every sense.

A group of evolutionary biologists from several American universities published an article in the journal Science, which presents the results of another rethinking of the mystery of the Cambrian explosion. Scientists have revised the relationship between the remains of ancient creatures, taking into account the latest finds, as well as the archaeological age of these finds. The genealogical relationships of fossil species with their modern descendants were clarified. In addition, data from molecular genetics were used: the researchers reconstructed the genealogy of several genes found in 118 modern species. All together, it made it possible to clarify the branching points on the family tree and determine exactly when a particular group began its own evolutionary path.

In general, the conclusions of the researchers boil down to the fact that the Cambrian revolution was preceded by a long invisible evolution. Over millions of years, organisms accumulated genetic and biochemical changes that in the Cambrian led to the emergence of different forms of life: the accumulated internal changes finally resulted in external changes. The authors compare this to the industrial revolution: inventions, small technological innovations accumulated for a long time without much change in the means of production, until finally they led to a global technological shift.

Accumulated genetic changes have been balanced for some time by the external environment and relationships between species. And from a biochemical point of view, different organisms already before the Cambrian could differ significantly from each other, demonstrating great biodiversity. Subsequently, the slightest ecological shifts should have been enough to allow the accumulated changes to manifest themselves from the outside. By the way, one of the very bold, albeit rather controversial hypotheses put forward in the article is the assertion that Precambrian animals ate each other more intensively: this may be one of the reasons for the scarcity of Precambrian fossil remains.

This is not to say that the new hypothesis has not attracted the attention of critics. Thus, one of the claims against the authors is that they did not take into account the so-called orphan genes, which make up approximately 30% of all animal genes. These genes have no homologue "relatives", and many believe that it was their sudden appearance that could have caused the Cambrian explosion of biodiversity. However, in this hypothesis, alas, there is the word "suddenly", from which science always tries to get rid of by all means.