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Recently, paleontologists, using the latest technology, found in sediments, which are 95 million years old, a snake. 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 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 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 the X-ray examination was able to show the scientists and 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. However, 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 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 squamopods 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.
Snakes are unusual appearance and behavior, attracting the enduring interest of scientists and admirers of reptiles. The appearance of these reptiles on the planet is attributed to the Cretaceous period, but their ancestors, ancient lizards, appeared much earlier, in the Paleozoic. And in this article you will find out what significance this reptile has in magic and everyday life.
The first reptiles originated in Africa more than 200 million years ago, subsequently spreading throughout the world, except for Antarctica.
Animal habitats are tropical areas, forests, steppes, mountain slopes and foothills. Reptiles can live in water, on land and trees. Sea snakes have gone into the deep waters of the ocean, breeding far from coastal areas. also inhabit freshwater lakes and rivers. The species diversity of snakes is about 3 thousand, which are combined into 23 families.
General Characteristics of Scaled Reptiles
Many species are poisonous, some reptiles are capable of inflicting deadly bites. Separate types use poison to paralyze prey. The elongated body of reptiles is completely covered with scales.
Some species can reach 12 meters in length. The smallest snakes are only 8 cm. Predatory individuals feed on insects, frogs, fish, bird eggs and small mammals. Certain types capable of swallowing prey several times larger than reptiles in size.
The color of the skin of reptiles is varied and often corresponds to color scheme natural environment environment. At first sight bright colors securely hide reptiles in tropical forests among lush greenery.
Some snakes are distinguished by variegated skin patterns, even in a rather faded environment, signaling danger to others. There are species that show a warning color only at the moment of danger.
The duality of the image in ancient mythology
In ancient times, snakes were a rather controversial symbol, combining the positive concepts of fertility, immortality, wisdom and the negative ones - evil, duplicity. The duality was based on the poisonousness of the reptiles, which brought death, and on the ability to regenerate and resurrect by shedding their skin. The animal is a symbol of healing and medicine.
Legends speak of the wisdom of these reptiles, who know the secret of eternal life and the secrets of healing recipes. way ancient god resurrecting Asclepius from the dead, an image appeared in the form of a staff entwined with a snake.
Among the huge variety of reptiles, snakes were a symbol of healing. The snakes were called the snake of Aesculapius and revered in Rome and. The symbol of modern medicine is depicted as a bowl of medicine wrapped around a snake.
Already
In Antiquity, the reptile was a sacred animal to the goddess Athena. In Egypt, the image of the goddess Isis was represented as half woman, half snake. Egyptian mythology associated the image of a snake with the Sun, as an attribute of the god Osiris. The snake combines cunning and deceit, dark forces and evil. Ancient beliefs endowed reptiles with the qualities of an intermediary between the earthly and other worlds.
The symbol of the reptile in the culture of Eastern countries
Chinese culture is filled with ancient legends and traditions related to snakes. In most tales, reptiles embody negative symbols and evil. lore Far East do not distinguish between the images of dragons and snakes.
Dragons acted as guardians of the temples, guarding esoteric knowledge and treasures. There is an opinion that represents a snake closed in a circle, as a reflection of the concept of yin-yang, symbolizing harmony and eternity.
The animal was considered bisexual, personifying fertility. The chthonic nature of the reptile embodied the power of dark magic and omniscience. Thanks to the ability to glide without the help of limbs, reptiles were considered an all-pervading creature, able to overcome any obstacles.
The black sun served as the image of sorcerers and witches, representing sin and the dark forces of nature. The Heavenly Serpent, or the Azure Dragon, was the symbol of the rainbow, embodying the transition between the worlds. In Japan, this animal is an invariable attribute of the gods of thunder and thunder.
The embodiment of the image in Christianity
The image of this reptile in Christianity is considered dually, combining wisdom and the chthonic symbol of the devil. The personification of the fall into sin and everything dark that must be overcome by man. The animal wrapping around the Tree of Life was a positive symbol, the snake on the Tree of Knowledge is the dark beginning, Lucifer.
The reptile, depicted with a female head, personified temptation. In Christian beliefs and culture, the animal personifies the negative image of a poisonous creature with the ability to wriggle, using lies and cunning. Popular beliefs endowed negative characters with a "serpent's heart", implying the malice and deceitfulness of the images.
Greek legends represent the snake, symbolizing healing and renewal. In Jewish legends, a reptile is always evil and sin. The image is widely represented in almost all mythologies and cultures of the world. Often the symbol was associated with fertility, male and female principles, home. Many magical texts contain an appeal to these animals as intermediaries between the worlds.
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The snake has always been a symbol of wisdom. These creatures in reality are not liked by everyone. For many people, snakes cause disgust and other conflicting feelings. It is also known that snakes appear in many legends. various peoples, especially those that tell about the creation of our world. So, for example, there is the World Serpent - a huge creature endowed with magic power. AT different countries he was described in his own way. I wonder if snakes could be our distant ancestors? Perhaps Darwin was wrong?
Ancestors of the snake - myths of different peoples
The Vedas tell us about the many-headed snake named Shesha. This snake lived in the waters of the prehistoric world ocean. He was allegedly tamed by the god Vishnu, after which he forced the monster to curl up into a ball, from which he made a bed for himself. The legend says that one day the moment will come when Shesha will wake up and pour poisonous fire on the entire planet, after which Vishnu will also wake up, who will need to tame the predator again and create new worlds.
Evenks talk about the World Serpent Diabdar, who was the first to be sent to the Earth, completely covered with water. He crawled across the untouched Earth, laying rivers and forming other reservoirs, after which the water went into them, freeing the territory for people.
In Scandinavian legends, there is also a similar character - an extra-large serpent named Jörmungandr. He keeps our planet in weightlessness, wrapped around it with his whole body.
The legends of some nations claim that it was the serpent that became the progenitor of man. Among the ancient Aztecs, one of the main gods was Quetzalcoatl - a serpent with a feathered body that created people. In China, they still remember the goddess Nuwe, who was something in common between a snake and a man. Legends say that she created people from clay.
The Hopi people call themselves the children of the snake. Even the Mongols have their own snake-patron and progenitor. The Mongols believe that Avraga Mogoi (World Serpent) created them.
Our direct ancestors - the Slavs constantly tried to "make friends" with snakes, brought them food and milk, if they found their shelter. They tried not to harm these creatures. Some Slavic settlements even worshiped snakes, periodically sacrificing the most delicious foods to them: cheeses, milk, eggs and meat. Among the Slavs, snakes were the patrons of the house. Logically, these living beings are useful in many ways. For example, they get their own food, besides, they are able to catch mice. Perhaps that is why snakes were respected and idolized.
In the distant past, India was called Nagadvipa - the country in which the "Nagas" live. "Nagas", in turn, it was customary to call snakes that could take the form of a person. Ancient Indian legends speak of the marriages of snake women with ordinary people, mostly rulers and heroes. Some sources claim that the Buddha himself was a descendant of the "nagas". If this is so, then it becomes clear why the skin color of the gods of India is so strange.
Sometimes the World Serpent was considered not a good progenitor, but an enemy and a killer.
In ancient Egyptian legends, the serpent Apep was always hostile to the god Ra. Every morning, Apep tried to eat the Sun of Ra so that the Earth would plunge into eternal night. But Ra always defeated the evil enemy, so the Sun appeared in the sky every day.
In addition, the creators of the Bible considered the bad World Serpent. It tells about the snake tempter who treated forbidden fruit Eve, after which people were expelled from Paradise so that they could independently learn how to get their own food.
The most interesting thing is that despite the attitude of the World Serpent to people, in all myths he remains wise. Thus, it can be assumed that all nations respected him, even if he was a negative character. Why does the serpent play an important role in mythology? After all, on our planet there have always been other, no less interesting and worthy animals.
prehistoric world of reptiles
Reptiles lived on our planet long before humans. They have evolved, changed, adapted over the course of several million years. These creatures survived the dinosaurs, which means they were able to withstand global changes climate that have occurred on Earth several times.
Snakes quickly explore new territories. They settle in abandoned temples, villages and various buildings. Then it is very difficult to drive them out of there, as predatory creatures bravely defend their territory to the last. People have always been afraid of snakes. The reason for this is the toxicity of many representatives of this family. Perhaps that is why snakes began to be treated with respect.
Zoologists say that snakes have a special talent to "survive". The speed with which they adapt to new conditions is amazing. Therefore, some uneducated peoples could consider snakes to be immortal.
Humans may have descended from snakes
In one of the hypotheses, it is said that a civilization of "serpentoids" - intelligent snakes - lived in front of people on Earth. This hypothesis is supported by some archaeological finds. For example, paleontologist D. Russell once found the most interesting remains of stenonychosaurs. After studying them, he came to the conclusion that at a certain time the size of the brain in these animals increased very quickly, just like in monkeys - the ancestors of man according to Darwin's theory. Based on this, the paleontologist suggested that stenonychosaurs could well have evolved into a reasonable creature, for example, into “serpentoids”. These ancient forerunners of humans have interesting description in legends: their height does not exceed 1.5 meters, their bodies were covered with thick scales, their limbs resembled human ones, but the number of fingers did not exceed three. "Serpentoids" could disappear from our planet due to global climate change.
Snakes, like other reptiles, have lived on Earth for tens of millions of years, but tracing their evolutionary origins has become a huge challenge for paleontologists. In the next 11 paragraphs of the article, you will find photos and descriptions of various ancient snakes, ranging from dinylysium to the largest prehistoric snake in the world - the titanoboa.
1. Dinilisia
Habitat: light forest South America;
historical period: late Cretaceous period (90-85 million years ago);
Size and weight: about 1.80-3m long and 5-10kg;
diet: small animals;
Distinctive characteristics: moderate size; dull skull.
The makers of BBC: Walking with Dinosaurs were pretty knowledgeable about prehistoric reptiles, so it's unforgivable that the last episode of Death of a Dynasty (1999) featured a huge bug involving the dinylysia snake.
This prehistoric snake has been shown to be a threat to young tyrannosaurs, despite the fact that: firstly, dinylysia lived 10 million years earlier than Tyrannosaurus Rex, and secondly, this snake was native to South America, while T -Rex lived in North America.
2. Epodophis (Eupodophis descouensi)
Habitat
historical period
Size and weight: about 1m in length;
diet: small animals;
Distinctive characteristics: small size; tiny hind legs.
Epodophis is a classic transitional form between lizards and legless snakes. These reptiles Cretaceous had tiny (about 2 cm) hind legs, with a characteristic femur and tibia. Ironically, the epodophis and two other genera (chaasiophis and pachyrahis) of fossil snakes equipped with rudimentary legs were discovered in the Near East, a clear breeding ground for snakes, 100 million years ago.
3. Gigantophis
Habitat: woodlands of North Africa and South Asia;
historical period: at the end of the Eocene (40-35 million years ago);
Size and weight: up to 10 m in length and up to 500 kg;
diet: small animals;
Distinctive characteristics: big size; capacious jaws.
Approximately 10 meters long and weighing about half a ton, the prehistoric snake Gigantophis, until recently was considered the most big snake ever lived in the world, until the remains of an ancient titanoboa snake, much larger (15 m in length and weighing about a ton), were discovered in South America.
4. Haasiofis
Habitat: woodlands of the Middle East;
historical period: late Cretaceous period (100-90 million years ago);
Size and weight: about 1m in length;
diet: small marine animals;
Distinctive characteristics: moderate size; tiny hind limbs.
Some paleontologists believe that the haasiophis was related to the older snakes of the genus Pachyrachis, but most of the evidence (mainly related to the shape of the skull and structure of the teeth) places these snakes in a separate genus.
Habitat: woodlands of South America, Western Europe, Africa and Madagascar;
historical period: Late Cretaceous-Pleistocene (90-2 Ma)
Size and weight: 3-9 m in length and weighing 2-20 kg;
diet: small animals;
Distinctive characteristics: moderate to large size; the structure of the vertebrae.
As you can guess from the unusually wide geographic and temporal range of snakes in the genus madtsoia (various species of madtsoia span a span of 90 million years), paleontologists are far from sorting out the evolutionary relationships of these prehistoric snakes.
6. Nyash (Najash rionegrina)
Habitat: woodlands of South America;
historical period: Late Cretaceous (90 million years ago);
Size and weight: about 1m in length;
diet: small animals;
Distinctive characteristics: moderate size; small hind limbs.
Unlike other genera of basal snakes: epodophis, pachyrahis and haasiophis, which spent most of their lives in the water, snakes of the genus Nayash led an exclusively terrestrial lifestyle.
7. Pachyrahis
Habitat: rivers and lakes of the Middle East;
historical period: Early Cretaceous period (130-120 million years ago);
Size and weight: up to 1 m in length and weighing about 1 kg;
diet: fish;
Distinctive characteristics: long serpentine body; small hind legs.
Pachyrahis is perfect intermediate form between lizards and snakes: these ancient reptiles possessed an exclusively serpentine body, complete with scales, a python-like head, and a pair of vestigial hind limbs located a few centimeters from the end of the tail.
8. Sanayeh (Sanajeh indicus)
Habitat: woodlands of India;
historical period: late Cretaceous period (70-65 million years ago);
Size and weight: up to 3.5 m in length and weighing 10-20 kg;
diet: small dinosaurs;
Distinctive characteristics: moderate size; limited articulation of the jaws.
Sanaeh (Sanajeh indicus) significantly inferior in size to the world's largest prehistoric snake, but this is the only species that hunted dinosaurs with great confidence (mainly cubs and small dinosaur species up to 50 cm in length).
9. Tetrapodophis
Habitat: woodlands of South America;
historical period: Early Cretaceous (120 million years ago);
Size and weight: 30 cm long and weighing several hundred grams;
diet: insects;
Distinctive characteristics: small size; four vestigial limbs.
Tetrapodophis has a dubious origin - it was allegedly discovered in Brazil, but no one can say exactly where and by whom, as well as how the fossils got to Germany. Some paleontologists doubt that tetrapodophis is a real prehistoric snake.
10 Titanoboa
Habitat: woodlands of South America;
historical period: Paleogene period (60 million years ago);
Size and weight: up to 15 m in length and weighing about 1 t;
diet: animals;
Distinctive characteristics: giant size; camouflage color.
Titanoboa is the largest prehistoric snake in the world that has ever lived on our planet. She reached up to 15 m in length and weighed about 1 ton. The only reason why she did not hunt dinosaurs is that the titanoboa appeared several million years after their death. In the article "," you can get acquainted with the mass interesting information about these giant snakes.
11. Wonambi
Habitat: plains of Australia;
historical period: Pleistocene epoch (2 million - 40 thousand years ago);
Size and weight: 5-6 m in length and weighing about 50 kg;
diet: animals;
Distinctive characteristics: big size; primitive head and jaws.
Although the Australian wonambi were not directly related to modern pythons and boas, these snakes had a similar hunting style: squeezing their muscular coils around unsuspecting animals and slowly choking them to death.
Where did snakes come from
Snakes have shown miracles of adaptation and evolutionary success since the dinosaurs disappeared from the face of the earth. But where did they come from? How did a four-legged reptile turn into a snake? Where are the transitional forms confirming such an evolution?
In fact, losing the legs is the simplest part of the transformation. This has happened to many groups of tetrapods, and they all evolved independently. Legless reptiles include not only snakes, but also a group of extant amphisbaenas, as well as some lizards, including individual skinks, Australian scale-legs, spindles and yellowbellies. Among amphibians, legless ones stand out ( Apoda), which developed worm-like bodies, as well as sirens, which retained shortened forelimbs and lost their hind limbs. In addition, at least two extinct groups of amphibians, aistopods and lysorophids, also became legless. Almost all of these animals burrowed into the ground, so without limbs it was obviously easier for them to make their way through the ground or soft silt. There is a simple reason why it is easy to lose limbs. The development of limb buds and the legs themselves is controlled by a certain set of Hox genes and Tbx genes: as soon as they stop giving the command to grow limbs, they disappear.
However, it seems unlikely to find a fossil snake that was in the limbless stage. As a rule, snakes do not fossilize well, because their body consists of hundreds of thin vertebrae and ribs, and they break and dissect. Single specimens are known from partially preserved or complete skeletons. Most fossil snakes have been found from several vertebrae, and the appearance of the animal is built on the scarce data on the shape of the spine.
Despite these obstacles, the fossil record contains many remarkable fossils that trace the transition from four-legged lizards to legless snakes. At the first stage, we find a lot of fragmentary fossils from jurassic. Followed by Adriosaurus microbrachis- a fossil animal found in 2007 in the Middle Cretaceous rocks (age - about 95 million years) on the territory of Slovenia (Fig. 13.3, BUT). This name translates as "Adriatic lizard with small front legs." Adriosaurus was a very thin-bodied, long marine lizard with fully functional forepaws but non-functioning vestigial hindlimbs.
Rice. 13.3. Adriosaurus Intermediate Fossil: This animal had tiny front legs but full hind legs :( BUT) skeleton; ( B) reconstruction appearance(Illustrations courtesy of M. W. Caldwell)
Next, we meet a variety of snakes that no longer have forelimbs, but still have tiny non-functional hind limbs. For example, Najash rionegrina was an earthen land snake; it was described in 2006 from fossils about 90 million years old found in the Candeleros Formation in Argentina (Nahash is the ancient biblical name for the snake that lived in the Garden of Eden). At Najash the pelvic girdle was preserved - vertebrae that articulated with the sacrum, as well as rudimentary hind limbs, in which there were femurs and tibias.
Even more specialized and serpentine are the extraordinary reptile fossils found in Late Cretaceous marine rocks in Israel and Lebanon. Of these fossils, the best preserved Haasiophis terrasanctus(Fig. 13.4). The name of this animal - Haas Snake from the Holy Land - was given in honor of the Austrian paleontologist Georg Haas, who discovered its location and managed to describe the fossil before his death in 1981. Haasiophys was found in limestone near the town of Ein Yabrud in the Judean Mountains, near the city of Ramallah on the West Bank of the Jordan River. The age of the fossil is 94 million years. It is an almost complete skeleton (88 cm long) with only the tip of the tail missing. The skull and most of the vertebrae look similar to those of most other primitive snakes. However, the hind limbs were also present here - very small, but with the femur, both tibia and part of the foot. Unlike the hind limbs Najash, pelvic bones Haasophis very small and no longer connected to the spine; they are completely rudimentary and useless. Haasophis and many other Cretaceous snakes seem to have had a vertical fin and paddle-like tail, like modern sea snakes.
Rice. 13.4. Bipedal snake haasiophis :( BUT) a fully articulated skeleton with preserved rudimentary hind limbs (large dark blocks - cork inserts, due to which nothing can be put on the sample); ( B) fragment of rudimentary hind limbs (illustrations courtesy of M. Polcyn, Southern Methodist University)
A slightly larger snake from Ein Yabrud is called pahirahis; Haas described it in 1979. Although these fossils are more fragmentary than those of the Chaasiophys, the meter-long body also has tiny vestigial hind limbs. The ribs and vertebrae of Pachyrahis are very thick and dense, which probably helped him swim at great depths in the Cretaceous seas.
The third snake from marine Middle Eastern limestones - Eupodophis descouensi, found in Lebanon (near Ein Yabrud) in rocks about 92 million years old (Fig. 13.5). The generic name of this animal means "real snake with legs", and the specific name is given in honor of the French paleontologist Didier Decoin. This creature was 85 cm long, about the same as the haasiophis, but its limbs were reduced even more than those of the bipedal snakes of the Cretaceous period: haasiophis and pachyrahis.
Rice. 13.5. Eupodophis bipedal snake :( BUT) complete skeleton with preserved rudimentary hind limbs; ( B) fragment of the spine, which also shows vestigial hind limbs (illustrations courtesy of M. W. Caldwell)
Thus, not only the rudimentary hind limbs of several extinct Late Cretaceous sea snakes, but also the rudimentary pelvic and thigh bones(sometimes with tiny “branches” extending from them) of primitive living snakes, in particular boas and their relatives, are mute but convincing evidence of the origin of snakes from four-legged creatures.
But what is the common ancestor of all snakes? The first ideas about this were expressed by one of the pioneers of paleontology and herpetology, Edward Drinker Cope, who noticed that anatomically, snakes are in many ways similar to monitor lizards, for example, Australian and Komodo ones (especially with mosasaurs - sea lizards of the Cretaceous period). Anatomical facts also seem to support the relationship of snakes with monitor lizards, but the latest data from molecular biology do not; they are ambiguous. Some molecular sequences allow snakes to be considered the closest relatives of monitor lizards, others do not allow them to be considered relatives of any of the currently existing families of lizards.
The view that snakes lost their limbs to the sea is probably supported by the many fossils of sea snakes from the Cretaceous rocks of the eastern Mediterranean (Slovenia, Israel, Lebanon). According to this version, the loss of auricles and the appearance of solid transparent snake eyelids may be due to adaptation to swimming, and not to a burrowing lifestyle.
Another school of zoology develops the idea that snakes may have descended from ground lizards rather than swimming lizards, such as the Kalimantanan earless ground monitor. Supporters of this idea believe that the transparent eyelids should have protected the snake's eyes from coarse coarse sand when buried in the ground, and the auricle could disappear, because without it dirt gets into the ear cavity less. "Land" adaptation traits Najash are consistent with this point of view, although he lived somewhat later than the sea snakes haasiophis, pachyrachis and eupodophis. The most primitive of all known snakes is the coniophys, which had a lizard head and a snake body. True, his fossil is too poorly preserved to be used to judge the limbs of the animal. Nevertheless, he was land, not sea. The water lizard adriosaurus is an even more primitive relative of snakes. She had four legs and swam in the ocean.
Accordingly, the mystery of the closest relatives of snakes has not yet been revealed. This is how science develops: contradictions like the ones mentioned above are very important for the scientific process, only in this way can we carefully study all the facts and not discard the available versions. Regardless of how the dispute is ultimately resolved, the fact is that many fossils have features that illustrate the transition from quadrupedal to bipedal to legless. This confirms that snakes are descended from four-legged ancestors.
