A new explanation for the mystery of the Cambrian explosion. Mysteries of paleontology - a giant mushroom or algae?! "Palaeontological mysteries of the Moscow region"
This mystery has haunted paleontologists for 150 years. Something called Prototaxites could not be confidently attributed not only to a family or genus, but to any biological kingdom. Only today, the analysis of fossils has made it possible, it seems, to determine this gigantic creature. ancient earth, which is why, however, it has not ceased to be extremely surprising.
The story of Prototaxites is an excellent example of what to see and understand - what do you see, as they say, two big differences. The American scientist J.W. Dawson, who was the first to describe this mysterious creature (in 1859), believed that these were fossils of rotten wood, somehow related to the current yew trees (Taxus), and therefore gave them the name Prototaxites. Only before the real yew trees, this creature had to “stomp and stomp”, because Prototaxites was widespread throughout the entire Earth, but only 420-350 million years ago.
At the end of the nineteenth century, scientists began to think that it was seaweed, or rather brown seaweed, and this opinion became stronger, ending up in encyclopedias and textbooks for a long time. Although it is difficult to imagine something like an algae (or a colony of algae?) growing in the form of a “trunk” of six and sometimes nine meters in height.
By the way, Prototaxites was the largest organism on land at that time: vertebrates had just begun to appear, so wingless insects, centipedes, and worms were crawling around the strange high “pillar”.
The first vascular plants, the distant ancestors of conifers and ferns, although they appeared 40 million years earlier, nevertheless, at the time when Prototaxites settled on Earth (in the Early Devonian), had not yet risen above a meter.
By the way, about the sizes. IN Saudi Arabia a 5.3 meter long specimen of Prototaxites was found, which has a diameter of 1.37 meters at the base and 1.02 meters at the other end. A trunk 8.83 meters long with a diameter of 34 centimeters at one end and 21 centimeters at the other was dug up in New York State. Dawson himself described a specimen from Canada - 2.13 meters long and maximum diameter at 91 centimeters.
What else is important to note regarding the structure of Prototaxites. It does not have the same cells that plants have. But there are very thin capillaries (tubes) with a diameter of 2 to 50 micrometers.
Nowadays, scientists, based on the results of many years of research on this representative of the ancient living world, have put forward new versions. Some experts, starting with Francis Hueber from the American national museum natural history (Smithsonian Institution, National Museum of Natural History), are inclined to believe that Prototaxites is a fruiting body huge mushroom; others say that it is a huge lichen. Latest version, with his arguments, was put forward by Marc-Andre Selosse from the University of Montpellier II.
One of the ardent supporters of the mushroom version is Charles Kevin Boyce, now working at the University of Chicago. He published several works dedicated to detailed study Prototaxites
Boyce never ceases to be amazed by this creature. "No matter what argument you make, it's still kind of crazy," says the researcher. "A mushroom that's 20 feet tall doesn't make any sense. No seaweed is going to be 20 feet tall. But here it is - a fossil - in front of us".
Recently, Francis Huber completed a titanic work: he collected many specimens of Prototaxites from different countries and made hundreds of the thinnest sections, taking thousands of photographs of them. Analysis of the internal structure showed that it is a mushroom. However, the scientist was disappointed that he could not find characteristic reproductive structures that would clearly indicate to everyone that this was indeed a mushroom (which gave confidence to Huber’s opponents from the “lichen camp”).
The latest (in time, but clearly not the last in the history of Prototaxites) evidence of the fungal essence of a strange organism of the Devonian period is an article by Huber, Beuys and their colleagues in the journal Geology.
“The large spectrum of isotopes found is difficult to reconcile with autotrophic metabolism, but it is consistent with the anatomy indicating a fungus and with the assumption that Prototaxites was a heterotrophic organism living on a substrate rich in various isotopes,” the authors of the paper write.
Simply put, plants get their carbon from the air (from carbon dioxide), and mushrooms come from the soil. And if all plants of the same species and the same era show the same isotope ratio, in mushrooms it will depend on the place in which they grow, on the diet, that is.
By the way, analysis of the ratio of carbon isotopes in different specimens of Prototaxites is now helping scientists to recreate the native ecosystems of this ancient creature. Because some of its specimens appeared to “eat” plants, others used the soil microbial community as food, and still others may have received nutrients from mosses.
A co-author discusses the mystery of the large growth of a Paleozoic mushroom this study, Carol Hotton, from the Smithsonian Museum of Natural History: she believes that the large size helped the fungus spread its spores further - across scattered swamps, chaotically scattered across the landscape.
Well, when asked how this mushroom grew to such monstrous sizes, scientists answer simply: “Slowly.” After all, there was no one to eat this mushroom at that time.
But what to do? Sections of fossils stubbornly “did not want” to resemble sections of trees, and in general they did not resemble a plant. By the way, rings on cuts are observed there, but these are not annual rings of trees.
Having again analyzed data on the structure of the mysterious extinct animal, scientists decided that it cannot
Strange fossils discovered back in the mid-20th century. in the territory American state Illinois, became the beginning of one of the most interesting riddles paleontology. In honor of the finder of the first sample, Fra
23:10 February 28, 2017Having again analyzed data on the structure of the mysterious extinct animal, scientists decided that it cannot be a fish, as was previously thought. The mystery of the Tullymonster remains open.
Strange fossils discovered back in the mid-20th century. on the territory of the American state of Illinois, became the beginning of one of the most interesting mysteries of paleontology. In honor of Francis Tully, who found the first sample, these creatures were called “tullymonsters”; today there are several hundred of them known. The remains are dated to about 310 million years old - at that time, this territory was located rich in life river delta. However, it is not possible to strictly classify these animals.
The prints of soft-bodied tullymonsters are too vague and uncertain, so paleontologists put forward a variety of versions about their structure and appearance, sometimes attributing them to mollusks or arthropods. In 2016, Victoria McCoy and her co-authors described them as relatives of lampreys: “Tullimonster is a vertebrate,” was the title of a paper they published in Nature. “Tullimonster is an invertebrate,” argues a new article published in the journal Paleontology.
Tullymonster could be anyone / Lauren Sallan
The authors of last year's article, having studied more than a thousand remains of tullymonsters, noted a light stripe running along the middle of the body, like a notochord, a primitive spine. Some other details reminded scientists of gill sacs and teeth, also characteristic of vertebrates - more precisely, jawless fish, relatives of modern hagfish and lampreys.
The authors of the new article dispute these interpretations. Lauren Sallan of the University of Pennsylvania and her colleagues note that the position of the elements that were mistaken for gill sacs shows that they were unlikely to be involved in respiration. The location of the part identified as the liver also does not agree with the structure of the vertebrate. In their work, Sallan and her co-authors looked at the anatomy of the Tullymonster's eyes.
Tullymonster Interpretation: Vertebrate / Nobu Tamura
They already had a rather complex structure and contained melanosomes - cells that accumulate the pigment melanin. However, the shape of the Tullymonster's eyes was still the most primitive, cup-shaped, devoid of a lens. “The problem is that if they have cupped eyes, then they can’t be vertebrates,” says Lauren Sallan, “because all vertebrates have more complex eyes, or have simplified them a second time. Moreover, many other creatures have such eyes - primitive chordates, mollusks and some worms.”
Tullymonsters and analogues of some other structures found in marine vertebrates were not found - traces of the auditory capsule, which serves the animal to maintain balance, and the lateral line, a sensory organ. “One would expect that at least some of the remains would have preserved them,” Sallan emphasizes. “It turns out that these creatures have something that vertebrates shouldn’t have, but they don’t have something that certainly should have existed and been preserved.”
Tullymonster print at the Natural History Museum in Milan / Wikimedia Commons
Thus, the authors again analyze the old data and make the assumption that the Tullymonster still belonged to some group of invertebrates. At the same time, no new research has been carried out, and many experts note that the mystery remains a mystery - neither on a mollusk, nor on a worm, nor on an arthropod strange creature also not at all similar.
New paleontological discoveries are changing established ideas about pterosaurs - and the most bizarre animals that have ever flown above the earth.
Pterosaur and pterodactyl are two names for strange flying creatures; The first of them translated from Greek means “wing-lizard”, the second means “flying finger”.
The remains of such an animal were first found in the 18th century. Since then, scientists have described more than 200 species of winged lizards, but popular ideas about these dragons that reigned in the sky Mesozoic era more than 160 million years, remains the same.
We invariably imagine them as sluggish but very dangerous flying reptiles with long beaks and leathery wings, striding on their hind legs like penguins.
Take, for example, the 1966 film One Million Years B.C., in which Raquel Welch's heroine is carried away by a shrill, squawking purple pterosaur to its nest to feed its young (spoiler alert: the bikini-clad beauty escapes). Has anything changed in 50 years? Not at all: in “The World Jurassic period”, filmed in 2015, pterosaurs still carry more than their own weight in people into the skies. (Just in case, let’s clarify: the last pterosaurs died out 66 million years ago, that is, an entire eternity before people appeared on Earth.)
A huge number of paleontological finds made in Lately, allows us to know that pterosaurs came in a wide variety appearance both size and behavior also varied greatly. Hundreds of species of pterosaurs lived simultaneously, occupying different ecological niches, just like birds today. Among them were giant monsters, such as Quetzalcoatlus ( Quetzalcoatlus northropi), one of the largest flying creatures known today: standing on all fours, it could rival the height of a giraffe, and its wingspan reached 10.5 meters. But there were also sparrow-sized pterosaurs: these sat on branches in ancient forests and, most likely, caught insects.
One of the most interesting finds is fossilized pterosaur eggs. By scanning those that were better preserved, scientists saw 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, who lived in China, and next to it was another, which apparently squeezed out under the weight of volcanic ash, covering the animal. Mrs. T (as this female was named) became the first pterosaur whose sex was accurately determined. There was no 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 discoveries, pterosaurs seem to have become closer to us, but scientists still can’t get enough. And on the way to national park Big Bend in southwest Texas, paleontologist Dave Martill from the University of Portsmouth shares with me his working plans: first, to meet rattlesnake and admire her; secondly, find a complete Quetzalcoatl skull. The chances of fulfilling the first point of the program are immeasurably higher.
The most important thing for a pterosaur specialist is to be an optimist. Imagining 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 starting to plan what you will spend the winnings on. Fossils of pterosaurs are extremely rare because their bones were hollow and thin. As for Quetzalcoatlus, we know about it thanks to just a few fragments found in Big Bend Park in the 1970s.
The hollow, ultra-light bones of pterosaurs were good for flight, but are very rarely preserved as intact as these anhanguera remains. In most cases, they are crushed, “as if a roller had passed over them.”
Martill and his colleague Nizar Ibrahim spent three days searching for fossilized bones in the dry riverbeds of the park's lands. They walked up and down the Pterodactyl Ridge (what a promising name!), every 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 the Milankovitch cycles!” exclaimed Martill, meaning that periodic changes in the shape of the Earth’s orbit and the tilt of its axis, as established by the Serbian astronomer Milutin Milankovic at the beginning of the 20th century, affect the climate planet, and this is reflected in the cyclic structure of sedimentary deposits). Having climbed onto a sandstone ridge, from which it seemed impossible to get down, Martill only said: “Where did ours go!”, jumped down and remained safe and sound.
However, the researchers were not able 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 they are not interested in dinosaurs.
Leaving the national park, paleontologists are developing a plan for a new search for Quetzalcoatlus - they really want to learn more about this amazing lizard, in which everything is unusual: its size, appearance, and behavior - this can be judged by the few fossils remaining from it.
INSTITUTE OF VERTEBRATE PALEONTOLOGY AND PALEOANTHROPOLOGY, BEIJING Some areas of the Zhecholoptera fossil from China show subtle traces of hairs or fluff. (For the first time, such integumentary structures were discovered by Soviet paleontologists in a Jurassic pterosaur.)
Ideas about pterosaurs have changed greatly, even in terms of their appearance and behavior. This is partly explained by the fact that until very recently, scientists had to base their conclusions on an extremely small number of samples.
Pterosaurs had, frankly, a very strange anatomy. It may seem that they were poorly adapted for life on the ground or in the air. Once upon a time they even thought that wing-lizards crawled on their bellies, or imagined them walking on their hind legs with long forelimbs stretched forward, like zombies, and folded wings dragging behind them like a cloak. Later, using fossil traces, it was established that pterosaurs moved on four limbs, but exactly how and where they put their wings was still not clear. And their flying abilities were so doubted that they were considered incapable of getting off the ground except by throwing themselves off a cliff.
“It’s quite common to find individuals whose head and neck were three or even four times longer than the body,” says biophysicist Michael Habib of the Natural History Museum of Los Angeles County. Even scientifically trained artists often make mistakes when depicting them. “They take a bird as a model, but they add webbed wings and a crest to it,” says Michael. “However, the body proportions of pterosaurs were not at all avian.”
Habib decided to reconsider the existing ideas about the biomechanics of pterosaurs using, firstly, a mathematical approach and, secondly, practical knowledge of vertebrate anatomy, which he acquired in his other work, namely in the laboratory of the University Medical School Southern California. 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 snatch a flying insect or dodge the teeth of a predator—evolved into the ability to, as Habib puts it, “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), became the first vertebrates to master flapping flight.
Using equations used in aircraft 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 they would large species the overload would cause the femurs to break. Taking off from four limbs is more practical.
“You need to jump up on your front legs, like a high jumper on your pole,” explains Habib. To take off from the water, pterosaurs used their wings in the manner of rowing oars: they pushed off the surface. And, again, like oarsmen, they had large, developed shoulders, which were often combined with strikingly small legs - to minimize drag in flight.
The pterosaur's wing was a membrane stretched from the shoulder to the ankle; and it was stretched by its extremely long flying (fourth) finger, which forms the leading edge of the wing. Specimens from Brazil and Germany show that the membrane was riddled with thin muscles and blood vessels. Additional rigidity was given to the septum by the protein strands that “stitched” it. Scientists now believe that pterosaurs could have slightly modified their wing profiles depending on flight conditions, by contracting muscles or turning their ankles inward or outward.
Changing the angle of inclination of the ossified tendon on the wrist - the pteroid - may have served the same purpose as the reversal of the slats in large modern aircraft– increased lift at low speeds.
In addition, in pterosaurs, flight was involved more muscles and a larger proportion of body mass than in birds. And in their brain, like that of 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 no longer appear as winged misunderstandings, but as skilled aviators. Many species appear to have been adapted for slow but very long flight over long distances; they could float over the ocean using weak, warm updrafts of air (thermals). There were also species that Habib calls superflyers: for example, the albatross-like Nyctosaurus, whose wingspan reached almost three meters, had gliding qualities, especially the distance it flew for each meter of descent, that were quite comparable to the characteristics of modern sports glider.
“Okay, everything is clear with the wings,” one paleontologist began one day after Habib’s lecture. “But what can you say about the heads?” In Quetzalcoatlus, for example, the skull could be three meters long, while the body was less than a meter. And Nyctosaurus had a long “mast” sticking out of its huge skull, to which a crest was probably attached.
Answering the question, Michael talked about the brain of pterosaurs, the mass of which, like those of birds, only slightly weighed down the huge head, spoke about the bones, which were hollow, also 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 multilayer plywood). And from the inside, the cavities were crossed with 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 “Terrible Gray Wolf hypothesis”: “If you have a big mouth, then you can swallow more. And the protruding comb could attract females.” Well, returning to the question of that paleontologist, 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 northeast of the country, and leads them through a dimly lit corridor of a seemingly ordinary office building. This is actually the Jinzhou Paleontological Museum. Its director opens the door of a small windowless storage room, and the visitors are exposed to what in any other museum would be the main attraction for visitors: all the shelves and almost the entire floor are occupied by specimens with surprisingly complete, in all the smallest details, remains of feathered dinosaurs, ancient birds and, of course, pterosaurs.
On a large, almost shoulder-high stone slab leaning against the wall opposite the door, one can see a large, scary pterosaur with a wingspan of four meters and tiny chicken-like hind legs - Zhenyuanopterus. Its elongated head is turned to the side and seems to consist of only jaws, and the teeth become longer and more closely intersecting each other as it approaches the beginning of the mouth. “This is so that it is convenient to catch fish while floating on the surface of the water,” explains Lu. Zhenyuanopterus is just one of three dozen species of pterosaurs that he has described since 2001 (many are still waiting to be studied, lying on the shelves).
NATIONAL MUSEUM OF NATURE AND SCIENCE, TOKYO The skull of the piscivorous anhanguera was preserved in its natural position - to the delight of paleontologists.
The Jinzhou Museum is one of ten similar paleontological museums scattered throughout Liaoning Province, which is a treasure trove of pterosaur fossils and one of the regions where the finds were made that have put China on the map in recent times. cutting edge paleontology.
In addition, Liaoning is the main arena of rivalry, and people from the outside compare what is happening here, not entirely, however, justifiably, with the “bone wars” that the pioneers of American paleontology, Othniel Charles Marsh and Edward Drinker Cope, waged with each other in the 19th century.
The parties to this rivalry are Lu, representing the Chinese Academy of Geological Sciences, and Shaolin Wang, whose fossil-filled office is located at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. These pundits, like Marsh and Cope, worked together early in their careers, then went their separate ways, and since then they have treated each other with animosity that is not publicized. “Two tigers cannot live on the same mountain,” their colleague Shunxing Jiang grins.
In the decade and a half that has passed since then, Lu and Wang have more than once surpassed 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 previous ones, as often happens in paleontology. However, the rival parties will have to make even more discoveries in the future. “They would have to work all day long for ten years to describe everything that they have already dug up,” one of the guests notes with envy. Hearing this, Lü raises his eyebrows in surprise: “I think ten years will not be enough.”
The success of Chinese scientists is explained not only by competition, but also by the fact that they found themselves in 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 first Cretaceous period, says Lü, in the local forests and small fresh lakes a very diverse community of organisms has developed - dinosaurs, the first birds, many pterosaurs and insects. Due to the fact that volcanoes erupted in the neighborhood from time to time, many animals died under the ash and ended up on the muddy bottom of the lakes. Victims of such disasters found themselves buried very quickly, sometimes even without access to oxygen to the remains; their tissues mineralized faster than they could decompose, and therefore survived. Paleontologists call such localities Lagerstätte (Lagerstätte is German for “deposit”). And yet, such finds still have to be dissected for months - cleared 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 pterygoid exhibition at the Beijing Natural History Museum that you begin to see fossils differently - as part of a once-great diversity.
For example, Jeholopterus is a pterosaur with a wide frog-like mouth, which scientists suggest hunted dragonflies and other insects. Here is the Ikrandraco, named after winged creatures from Avatar: he probably flew low above the surface of the water and fished for fish using something like a keel on lower jaw. Here is a dungaripterus (Dsungaripterus) found in Northern China with a thin, upward-curved beak, which it used to pry mollusks and other invertebrates in order to then crush their shells and shells with its tuberculate teeth.
And all this disappeared at the end of the Cretaceous period, 66 million years ago. What was wrong with pterosaurs that eventually went completely extinct? Perhaps the animals they hunted have disappeared? Or, in the course of evolution, they reached such gigantic sizes that they could not survive global catastrophe, like an asteroid impact, while the little birds survived?
However, when you look at their perfectly preserved remains in the museum, you don’t think about that - 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.
Herbivorous, shell-covered ankylosaurs are famous for their massive “club” at the end of their tail, which apparently served as a weapon for their defense. But experts also know another intriguing feature: the vast majority of the discovered remains of these dinosaurs were buried belly up.
Discussions on this topic began back in the 1930s, and until now a lot of hypotheses have emerged, the most important of which were recently tested by a group of paleontologists led by Jordan Mallon from the Canadian Museum of Natural History. But first, they were convinced that the “ankylosaur orientation problem” was not a historical myth. Scientists reviewed 36 finds made in Canada and the reports of their authors, confirming that 26 of them were indeed upside down. This cannot be explained by chance.
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The authors then began testing key theories that explain this phenomenon. The first of them suggests that ankylosaurs were rather awkward in their movements and, having fallen on their backs, could not turn over, and predators knocked them over onto their backs, reaching their belly, which was unprotected by armor plates. Scientists did not find any evidence of this, and teeth marks were found only on one of the studied samples. “If ankylosaurs were so clumsy, they probably would not have survived for about 100 million years,” adds Jordan Mallon.
Another hypothesis believes that everything is connected with the shape of the armored body of ankylosaurs and with the location of their center of gravity. When the animal died and was decomposed by bacteria, its belly would swell, which could naturally turn it upside down. In favor of this hypothesis, it is usually indicated that this happens with modern armadillos. However, when Mallon's colleagues themselves examined 174 carcasses of animals hit by cars, there was no confirmation of this. The authors also followed the decomposition of some dead armadillos, and none of them “naturally” turned over on their backs.
Another model explains the orientation of the remains by the fact that the bodies of dead animals could end up in a body of water, afloat, and easily turn over under their own weight. Subsequently, they ended up at the bottom or aground and were covered with sedimentary rocks already in this inverted position. To test this theory, Mallon and his co-authors developed three-dimensional computer models of the buoyancy of the bodies of the two main varieties of ankylosaurs (ankylosaurs and nodosaurs), taking into account their bone density, lung capacity, etc.
By placing the models in a virtual river and “inflating” their bellies—as if by the gases that gut bacteria continue to release after death—the scientists monitored their behavior. In the case of the dinosaur, the hypothesis worked: even a small random deviation was enough for the body to turn upside down while afloat. Ankylosaurids turned out to be more stable, but the wave was strong enough and they switched to a more stable inverted orientation. This is exactly what apparently happened once in nature, leaving paleontologists one of the many, and now solved, mysteries of dinosaurs.
Mysteries of the "Cambrian period"
Kirill ESKOV
One of the mysteries of paleontology is the “sudden” appearance of most types of animals in the Cambrian period. Where did this riot of life come from? What happened before this? It turns out that the “Cambrian attempt” was not the only one. It was preceded by less successful versions of the “act of creation”, which gave rise to a lush fauna that disappeared without a trace.
In the long line of scientific merits of Charles Darwin, there is one: in “The Origin of Species,” published in 1859, he honestly and clearly formulated a number of questions to which his theory did not provide a satisfactory answer (given the then level of knowledge).
One of the most serious issues founder evolutionary theory considered the “mystery of the Cambrian.” It is known that fossil representatives of almost all the main divisions of the animal kingdom appear almost simultaneously in Cambrian deposits. In theory, their appearance should have been preceded by a long period of evolution, but for some reason there are no real traces of this process: there are no fossil remains in the pre-Cambrian (Precambrian) layers. None. Why don't you like "act of creation"?
The largest divisions of the geochronological scale are the zones: phanerozoic (from the Greek “phaneros” - visible, obvious, and “zoe” - life; the earliest period of this zone is by whom 
Bry) and Cryptozoic ("krypton" - in Greek "hidden"), or Precambrian. The fundamental division of the geochronological scale into the Phanerozoic, the most early period which is the Cambrian (beginning 0.54 billion years ago) and Precambrian (0.54 - 4.5 billion years ago), is based on the presence or absence in the corresponding sedimentary rocks of fossil remains of organisms that had a hard skeleton.
For almost a hundred years after the publication of the Origin of Species, there was virtually no increase in clarity on this issue. Overall, the Precambrian truly remained the “Dark Ages” of paleontological history, with virtually no “written sources” from it. All ideas about this period (and this is, after all, seven-eighths of the existence of our planet!) were conjectures, the verification of which seemed impossible.
The situation has changed only in recent decades: a real revolution has taken place in the study of Precambrian fossils, the most interesting results of which (as usual!) remain practically unknown to the general public. Partially paint over it" White spot" and this is the purpose of this article.
Idyll of the "Ediacaran garden"
In 1947, in Ediacara, South Australia, one of the most remarkable discoveries in the history of paleontology was made. It turned out that at the end of the Precambrian - Vendian period (620-600 million years ago) there was a rich fauna of amazing non-skeletal organisms, it was called Ediacaran. Thus, the period of reliable existence of multicellular animals on Earth has been extended by almost 100 million years. Subsequently, Ediacaran fauna was found in several other areas of the world (Namibia, Newfoundland, White Sea); Moreover, it turned out that these creatures had been found many times before (for example, in Ukraine in 1916), but were mistaken for inorganic remains.
What is remarkable about this fauna? All numerous groups of multicellular organisms that appeared at the beginning of the Cambrian were represented by small organisms (millimeters or first centimeters), the Ediacaran fauna consisted of large or very large invertebrates size up to one and a half meters. Among them were both radially symmetrical forms, called “medusoids,” and bilaterally symmetrical ones; some of them (petalonams) look like modern corals" sea feathers", others (like Dickinsonia and Spriggina) - annelids and arthropods. The first researchers of the Ediacaran fauna considered these forms to be the real ancestors of modern coelenterates and worms and included them in the corresponding types and classes of animals. This point of view still has supporters today (the “Australian school”). However, most researchers believe that the similarity here is purely external, and Ediacaran organisms (they were called Vendobionts) represent something completely special and not related in any direct way to modern groups animals.
First of all, vendobionts have a different body plan from the Phanerozoic animals we are used to. In almost all bilaterally symmetrical Vendian organisms, this same symmetry is somewhat broken - in the “segmented” forms, the right and left halves of the “segments” are shifted relative to each other, approximately the same as in a zipper or on a herringbone car tread. This asymmetry was usually attributed to the deformations of bodies during the burial process, until M.A. Fedonkin did not pay attention to the fact that the violations were suspiciously regular and uniform. He proved that vendobionts are characterized by a special structural plan, which mathematicians call grazing reflection symmetry; Among multicellular animals, this type of symmetry is extremely rare.
On the other hand, B. Rannegar found that in vendobionts an increase in body size during individual development the body is achieved through isometric growth, when all proportions of the body remain unchanged (as with a simple increase in the image of an object). Meanwhile, all known multicellular organisms, including the most primitive ones, such as coelenterates and worms, have not isometric, but allometric growth with a natural change in body proportions (for example, in a person in the series “embryo-child-adult” the absolute size of the head increases, while the relative size decreases).
There are also more specific objections to the classification of Ediacaran organisms as modern animal taxa. Under pressure from these arguments, supporters direct relationship between the Ediacaran and Phanerozoic animals, the Vendobionts were “surrendered” one at a time (“Yes, it seems that Spriggina is not a real arthropod after all...”), and this continued until A. Zey-lacher (it was to him (by the way, the term “vendobionts” itself belongs to) did not offer a fundamentally different solution to this problem. Having summed up the characteristics of the Vendian animals, he also cited a common feature for them: they are various variants of a wide ribbon with swellings. This type of organization (Seylacher called it a "quilt") is completely different from all that currently exists. Apparently, such a structure plan is a special way to achieve large body sizes with non-skeletal forms.
Zeilacher believes that the body shape of the Vendobionts (“quilt”), with its very high surface-to-volume ratio, allowed them to absorb oxygen and metabolites from the water over the entire surface of the body. Indeed, the largest Ediacaran organisms have neither a mouth nor even a semblance of digestive system. Feeding through the surface of the body (this method of feeding is called “osmotrophic”), these creatures did not need internal organs.
Recently, however, D.V. Grazhdankin and M.B. Burzin suggested that the bodies of Vendobionts were not a thick “quilt” at all, but a thin corrugated membrane - by analogy it can be called an “egg carton”. In fact, it is not the membrane itself that ends up in the burial, but those “sand cakes” that are obtained when its “holes” are filled with agitated sediment. These “egg cartons”, having an ideal volume-to-surface ratio, lay motionless on the bottom, absorbing sea water organic matter dissolved in it.
In addition, many researchers believe that these flat (and apparently transparent) creatures were literally stuffed with symbiotic single-celled algae, which made them practically independent of external sources food. Their modern ecological similarity can be the so-called autotrophic animals (it is estimated that coral polyps get up to 70 percent of their food from symbiont algae).
So, in the shallow waters of the Vendian seas there was an amazing ecosystem of “osmotrophic animals”. Thousands of specimens of various representatives of the Ediacaran fauna are now known, but none of them show damage or bite marks; Apparently, at that time there were no predators, or indeed animals that fed on large pieces of food. Therefore, the Vendian biota is often called the “Ediacaran Garden” by analogy with the Garden of Eden, where no one ate anyone. The situation of the Garden of Eden, as it should be, did not last long: at the end of the Vendian, the Vendobionts completely died out, leaving no direct descendants. The Ediacaran experiment, the first attempt in Earth history to create multicellular animals, ended in failure.
Weren't we also "quilts"?
However, there are other opinions regarding the fate of the Ediacaran fauna. In addition to two opposing positions - the “Australian school” and Zeilacher - there is also a “compromise” one. Its supporters believe that the Ediacaran fauna, in addition to the Vendobionts themselves, unique in their organization and characteristic only of this time (and also, possibly, relics of some pre-Vendian faunas), also contains distant ancestors of some Phanerozoic groups.
In this regard, oddly enough, chordates are remembered - the group that crowns the “tree of life”. Let us recall the symmetry of gliding reflection characteristic of vendobionts (and completely atypical for modern animals): elements of such symmetry are found precisely in the structure of the most primitive of chordates - the lancelet. At the same time, one of the Ediacaran organisms - Jurnemnia - with its sac-like body and two “siphons” is very reminiscent close relative chordates - ascidian; In addition, it turned out that the prints of this organism are highly enriched in vanadium, the same metal that serves as the basis for the respiratory pigment of ascidians. So some researchers do not rule out that you and I (as representatives of chordates) descend directly from the most ancient multicellular organisms on Earth - vendobionts.
This, however, is not yet the most exotic hypothesis regarding the nature and family ties Wendobionts. They were declared to be all sorts of things, even giant sea lichens! For example, A.Yu. Zhuravlev proposed a very ingenious hypothesis regarding the relationship of some Ediacaran organisms with giant (up to 20 centimeters in diameter) deep-sea multinucleated xenophyophore amoebae.
Such discrepancies in hypotheses can make a depressing impression on an outside observer, but in “justification” for scientists studying Precambrian organisms, the following must be said. The problem they solve is perhaps the most difficult in all of paleontology, because the actualistic method of reconstruction (by analogy with modernity) clearly works here at the very limit of its resolving power. Paleontologists are actually in the position of astronauts faced with the fauna of an alien planet, with the only clarification that they are forced to deal not with the alien creatures themselves, but with the “shadow theater” created by them.
“Knowledge is Power”, 2001, No. 6