Modern lobe-finned fish are representatives of the oldest species, which was considered completely extinct about 70 million years ago. But in 1938, the rarest individual was caught in the Indian Ocean off the southern African coast. The second time such a fish was caught in the same area. All caught individuals were thoroughly studied and taken under protection.

Who are lobe-finned fish?

These are the oldest representatives that appeared about 406-360 million years ago. Their remains were found in the marine and fresh environment on different parts. Scientists suggest that in their habitats there could be a lack of oxygen, which caused some features in the structure of their fins and respiratory system:

• powerful muscles;
• the skeleton resembled a brush with branched parts, which served as the basis for the name;
• double breathing (including pulmonary).

The length of these representatives could reach up to 7 m, they led a sedentary lifestyle, mainly along the bottom of reservoirs. They had numerous conical teeth, which led to the conclusion that these fish were predators.

Among scientists there is a hypothesis that the first amphibians arose from representatives of the crossoptera. But this theory has not been fully proven, but there are arguments in its favor:

• well-developed muscles helped to get out on land;
• available, in addition to gill, also pulmonary respiration;
• the rear nasal openings that the crossopterans had allowed them to smell approaching prey.

According to scientists, all representatives of this species died out about 70 million years ago, so the lobe-finned fish caught in 1938 became a real sensation. The inspired specialists decided to try to catch more fish. It turned out that there was a whole population that was located near the Comoros.

The discovered fish was given the name coelacanth. Until 1998, there was only one species of this genus, but then another species of coelacanth was caught off the Indonesian coast. They live at a fairly large depth and are nocturnal. Like their ancient ancestors, they are predators, which confirms the presence of many sharp teeth. During the day they hide in the thickets, and at night they swim out to hunt - for fish and squid. But the coelacanths themselves can become prey for more large species fish, such as sharks.

Modern representatives are not much different from their ancient relatives. They have a powerful tail, strong fins with well-developed muscles, but the skull is almost completely filled with a fat-like fluid. There are 7 fins in coelacanth, 6 of them are well developed and very much resemble limbs. When she moves, she leans on paired fins and touches them. But this rarely happens, because the fish are almost all the time at the bottom of the sea.

Modern lobe-finned fish the color is bluish-gray with large gray-white spots that are located throughout the fish body. The pattern that results from these spots is individual for each fish, which helps when observing them.

This coloration has another purpose - it is a good camouflage, because the light spots are a reflection of the area in which they live. By this coloration, two types of coelacanth can be distinguished: in the dying Comoros, the color changes from blue to brown, and in the Indonesian variety, the color always remains brown with a golden sheen on white spots.

Crossopterygian breeding

Coelacanths are ovoviviparous. The eggs have a bright orange color, their diameter is 9 cm and their weight is about 300 g. Pregnancy in these fish lasts 13 months, and the body length of their cubs reaches 33 cm. Thanks to scientific research, it turned out that they have a developed and complex for fish reproductive system. The eggs have a sufficient supply of yolk, which allows the embryos to feed on it and get enough oxygen.

After reaching sexual maturity, females breed once every few years. It is not known for certain how internal fertilization occurs in coelacanths and where young individuals then live after birth. No juveniles were found during underwater surveys and only two juveniles were found floating freely in the water column.

Cross-finned fish are tropical fish that live in the seas at a depth of about 100 m. In those deep waters in which coelacanths swim, there is little food for them, so at night they rise a little higher. This choice of habitat is due in individuals of both species to the fact that they feel comfortable at a temperature of 16-18 degrees. It is not surprising that at night the fish move to the upper layers of the water, because the nocturnal environment does not cause discomfort. During the day, coelacanths return back and move little, which can be associated with energy savings. There is an opinion that if it is raised to the surface, where the temperature exceeds 20 degrees, then the coelacanth experiences such severe stress that even placing it in cold water does not help.

Until 1997, it was believed that representatives of the loaches lived only in the southwestern region of the Indian Ocean, in the center of which the Comoros Islands are located. That is why the type of coelacanth found there was called Comorian. Later, another specimen was discovered off the coast of Indonesia. Scientists began to think that given fish accidentally ended up in those waters, but later it was proved that this is an independent type of coelacanth. There were repeated catches off the coast of Kenya, a permanent population was found in the South African bay, which expanded the range of the Locustidae along the entire coast of South Africa.

1. The emergence of coelacanths, which scientists have discovered.
2. Others may have been able to adapt to breathing on land and using strong fins to get out of the water. Therefore, there is a hypothesis that such coelacanths became descendants of terrestrial creatures.

Ways to save them

When, thought to be extinct, the fish was caught off the Comoros, they were French territory. Therefore, only the French were allowed to catch them, but the country presented the caught coelacanths as a diplomatic gift. During large-scale studies that were carried out in the 80s, it was believed that chordate fluid prolongs life. Then a black market was formed, where the cost of one fish reached large sums. After that, the Comorian coelacanths became on the verge of extinction, and measures were taken to save the species.

A special council was created, which dealt with the conservation of the species. After the research, it turned out that the previously declared number of individuals is overestimated. The measures taken to save the population have led to a constant number of the Comorian species. In 2009, their number was 300-400 individuals.

Modern lobe-finned fish are endangered due to the fact that they have a small range, specific physiology and image. Latimeria is unique not only because it is a representative ancient group fish, but it may be an important evolutionary link for the appearance of land creatures. Therefore, you need to try to preserve this rare species.

Meanwhile, in the Late Ordovician, in the Lower Silurian, people already sailed in the sea armored jawless fish . Silurian and Devonian - the time of their heyday. The head and front part of the body of many of them were covered by a bone shell, and the back part of the body that was not protected by it was carried on its skin. sharp teeth!

Significant moment. The world began to bite! Nature invented teeth! She dressed her first vertebrate children with chain mail made of small sharp teeth. Then part of the teeth moved into the mouth - on the jaw. By that time, it must be said, jaws (from the first gill arch) had already appeared in the ancient pre-fishes. And this means that they have already become real fish!

« Acanthodia were the oldest representatives of jawed vertebrates. , whose fossil remains are already known from the Silurian. Acanthodia were, therefore, contemporaries of specialized jawless vertebrates and could only come from more primitive forms that lived in the Ordovician and left behind only traces in the form of scattered small skin teeth ”(Academician I. Schmalhausen).

The most primitive owners of the chord: both tunicates and lancelets are the eternal inhabitants of the seas. From this ". it follows that the initial differentiation of vertebrates certainly took place in the sea, and their subsequent history could also play out in fresh waters. This is a question we need to discuss a bit here.

Two American researchers, Romer and Grove, suggested in 1935 that vertebrates originated in fresh waters. However, in 1950 W. Gross, using more extensive material, obtained the opposite result, which is fully consistent with my own opinion. Gross calculated that in the Upper Silurian, 64 percent of all fish-like animals lived in the sea, while in the Lower Devonian, only 19 percent ”(O. Kuhn).

The numbers show that the heyday freshwater fish came in the Lower Devonian. And, perhaps, as Professor O. Kuhn suggests, their mass migration from the seas to the rivers took place precisely at that time.

However, there is an opposite argument. Academician L. Berg (many scientists agree with him) believes that vertebrates passed the early stages of their evolution in rivers and lakes.

« bony fish appear in freshwater deposits of the Devonian immediately in the form of numerous forms ”(Academician I. Schmalhausen).

These are some freshwater bony fish we are now especially interested, because from them the first four-legged inhabitants of the land descended.

Fish that lived 400-350 million years ago in rivers and lakes breathed with both gills and lungs. That's why they called them lungfish. Without lungs, they would suffocate in the musty, oxygen-poor water of primeval lakes.

Some of them chewed plants with millstone teeth (the so-called real lungfish). Others, with cross-feathers, ate everything they could catch. They attacked from an ambush and, grabbing prey, poisoned it with poison. It drained from the palatine gland down the tubules on the teeth. (Unless the ichthyologists were wrong in thinking that the lobe-finned premaxillary gland was poisonous.)

Later lobe-finned fish from the group of coelacanths moved back to the sea. But they were not lucky there: they suddenly died out (all except the famous coelacanth, the discovery of which recently made so much noise).

The brushfins, who remained faithful to fresh waters, had a great future: they were destined to give birth to ichthyostegs - the direct ancestors of all four-legged and feathered inhabitants of the land.

The ancient fish with lungs had amazing paw-like fins with a jointed, brush-like skeleton, very mobile and muscular. On these fins they crawled along the bottom. Probably, they also climbed ashore in order to calmly breathe and relax here. (The land at that time was deserted - perfect place for those seeking solitude.) Gradually, the stilted fins turned into real paws. The fish came out of the water and began to live on land.

But what reason prompted the fish, which, presumably, felt quite well in the water, to leave their native element? Lack of oxygen?

No, there was enough oxygen. When there was little of it in the musty water, they could rise to the surface and breathe clean air. So, the lack of oxygen in the water could not be the reason that forced the fish to change their place of residence.

Maybe hunger drove them to land?

Also not, because the land at that time was more deserted and poorer in food than the seas and lakes.

Maybe danger?

No, and not a danger, since lobe-finned fish were the largest and most powerful predators in the lakes of that era.

The desire to stay in the water - that's what prompted to leave the water! It sounds paradoxical, but this is precisely the conclusion that scientists have come to by carefully examining possible reasons. In that distant era, shallow land reservoirs often dried up. Lakes turned into swamps, and those into puddles. Finally, puddles dried up under the scorching rays of the sun. The lobe-finned fish, which, on their amazing fins, were able to crawl well along the bottom so as not to die, had to look for new shelters, new puddles filled with water.

In search of water, the fish had to crawl along the coast for considerable distances. And those who crawled well survived, who could better adapt to land image life. So gradually, thanks to the harsh selection of fish that were looking for water, they found a new home. They became inhabitants of two elements - water and land. There were amphibians, or amphibians, and from them - reptiles, then mammals and birds. And finally, a man walked across the planet! Here we are too far ahead of ourselves. So far, a man has turned out from a giant “frog”, almost 400 million years have passed. So let's go in order. Next up are amphibians.

Origin of amphibians

It is believed that favorable conditions for the emergence and formation of amphibians about 385 million years ago (in the middle of the Devonian period) climatic conditions(warmth and humidity), as well as the availability of sufficient food in the form of already formed numerous small invertebrates.

And, in addition, during that period, a large amount of organic residues was washed into water bodies, as a result of the oxidation of which, the level of oxygen dissolved in water decreased, which contributed to the formation of changes in the respiratory organs in ancient fish and their adaptation to breathing atmospheric air.

Ichthyostega

Thus, the origin of amphibians, i.e. the transition of aquatic vertebrates to a terrestrial way of life was accompanied by the appearance of respiratory organs adapted to absorb atmospheric air, as well as organs that facilitate movement on a solid surface. Those. the gill apparatus was replaced by lungs, and the fins were replaced by five-fingered stable limbs that serve as a support for the body on land.

At the same time, there was a change in other organs, as well as their systems: the circulatory system, nervous system and sense organs. The main progressive evolutionary changes in the structure of amphibians (aromorphosis) are the following: the development of the lungs, the formation of two circles of blood circulation, the appearance of a three-chambered heart, the formation of five-fingered limbs and the formation of the middle ear. The beginnings of new adaptations can also be observed in some groups of modern fish.

ancient crossopterans

Until now, there has been controversy in the scientific world about the origin of amphibians. Some believe that amphibians originated from two groups of ancient lobe-finned fish - Porolepiformes and Osteolepiformes, most others argue in favor of osteolepiform lobe-finned fish, but do not exclude the possibility that several closely related phyletic lineages of osteolepiform fish could develop and evolve in parallel.

Shell-headed amphibians - stegocephals

These same scientists suggest that the parallel lineages later died out. One of the specially evolved, i.e. mutated species of ancient lobe-finned fish was Tiktaalik, which acquired a number of transitional characters that made it an intermediate species between fish and amphibians.

I would like to list these signs: a shortened head, separated from the belt of the forelimbs, resembling a crocodile, shoulder and elbow joints, a modified fin that allowed him to rise above the ground and occupy various fixed positions, it is possible that he can walk in shallow water. Tiktaalik breathed through the nostrils, and the air into the lungs, perhaps, was pumped not by the gill apparatus, but by the buccal pumps. Some of these evolutionary changes are also characteristic of the ancient lobe-finned fish Panderichthys.

ancient crossopterans

Origin of amphibians: the first amphibians

It is believed that the first amphibians Ichthyostegidae (lat. Ichthyostegidae) appeared at the end of the Devonian period in fresh water. They formed transitional forms, i.e. something between the ancient lobe-finned fish and the existing ones - modern amphibians. The skin of these ancient creatures was covered with very small fish scales, and along with paired five-fingered limbs, they had an ordinary fish tail.

From the gill covers they have only rudiments left, however, from the fish they have preserved the cleithrum (a bone belonging to the dorsal region and connecting the shoulder girdle to the skull). These ancient amphibians could live not only in fresh water, but also on land, and some of them crawled out onto land only periodically.

Ichthyostega

Discussing the origin of amphibians, one cannot but say that later, in the Carboniferous period, a number of branches were formed, consisting of numerous superorders and orders of amphibians. So, for example, the superorder Labyrinthodonts was very diverse and existed until the end of the Triassic period.

In the Carboniferous period, a new branch of early amphibians, the Lepospondyli (lat. Lepospondyli), was formed. These ancient amphibians were adapted to life exclusively in water and existed until about the middle of the Permian period, giving rise to modern amphibian orders - Legless and Tailed.

I would like to note that all amphibians, called stegocephals (shell-headed), which appeared in the Paleozoic, died out already in the Triassic period. It is assumed that their first ancestors were bony fish, which combined primitive structural features with more developed (modern) ones.

Stegocephalus

Considering the origin of amphibians, I would like to draw your attention to the fact that most of all the armored-headed fish are close to the lobe-finned fish, since they had pulmonary respiration and a skeleton resembling the skeletons of stegocephals (shell-headed).

In all probability, Devonian, in which the shell-headed ones were formed, was distinguished by seasonal droughts, during which many fish lived "unsweetened", since the water was depleted in oxygen, and the numerous overgrown aquatic vegetation made it difficult for them to move in the water.

Stegocephalus

In such a situation, the respiratory organs of aquatic creatures had to change and turn into lung sacs. At the beginning of the occurrence of breathing problems, ancient lobe-finned fish simply had to rise to the surface of the water to receive the next portion of oxygen, and later, in the conditions of drying up of reservoirs, they were forced to adapt and go to land. Otherwise, animals that did not adapt to new conditions simply died.

Only those aquatic animals that were able to adapt and adapt, and whose limbs were modified to such an extent that they became able to move on land, were able to survive these extreme conditions, and eventually turn into amphibians. In such difficult conditions, the first amphibians, having received new, more advanced limbs, were able to move overland from a dried-up reservoir to another reservoir, where water was still preserved.

Labyrinthodonts

At the same time, those animals that were covered with heavy bone scales (scaly shell) could hardly move on land and, accordingly, whose skin breathing was difficult, were forced to reduce (reproduce) the bone shell on the surface of their body.

In some groups of ancient amphibians, it was preserved only on the belly. I must say that the shell-headed (stegocephalic) managed to survive only until the beginning mesozoic era. All modern, i.e. The present orders of amphibians were formed only at the end of the Mesozoic period.

On this note, we end our story about the origin of amphibians. I would like to hope that you liked this article, and you will return to the pages of the site again, plunging into reading wonderful world living nature.

And in more detail, with the most interesting representatives of amphibians (amphibians), you will be introduced to these articles:

Loop-finned fish are one of the most ancient species fish known to mankind. Until the beginning of the twentieth century, they were considered extinct about 70 million years ago. Their fossilized remains have been found in many freshwater and marine reservoirs of the planet. Careful inspection of the fossils led scientists to assume that these fish belonged to the category of rather serious predators. Numerous conical teeth, powerful muscles and a fairly decent body length (from 7 cm to 5 m) made this animal a serious contender in any aquatic environment.

The lobe-finned fish got their name from the unusual structure of the skeleton of fleshy fins. It consisted of several brush-shaped branched segments. Such a structure of the fins not only allowed the fish to spend a fairly large amount of time at the bottom of the reservoir, but also successfully move along the bottom with the help of fins. The main result of such movements was a rather powerful musculature.

After weighing all the data obtained, modern scientists have come to the conclusion that general characteristics fish allows us to draw a parallel between lobe-finned fish and the first amphibians. This conclusion suggests itself on the basis of some curious features that both classes have. One of the confirmations of such a theory was called Tiktaalik. A creature belonging to the cross-finned fish, endowed with the appearance of a crocodile, had the greatest number of features that unite it with amphibians. He possessed gills and lungs, and the fins almost resembled the structure of the limbs of an animal.

Based on all of the above, science has come to the conclusion that the superorder lobe-finned fish took a direct part in the evolution of amphibians, gave life to other creatures on earth, and completely died out.

However, this statement was considered correct only until 1938, when an unusual fish caught in South Africa created a huge sensation among scientists. Looking at another catch in an ordinary fishing trawler, Ms. Latimer came across a strange blue fish, about 150 cm long and weighing about 57 kg. With her find, the woman went to the museum, however, there she could not decide on species affiliation instance. With no way to keep the fish alive, Latimer, with the help of a taxidermist, made a stuffed animal of this creature. What was the surprise of the famous professor Smith when in this exhibit he saw all the characteristics of a representative of the crossopteran order. After a thorough examination and analysis of the find, this fish was named after the woman who opened it to the light. Now Latimeria chalumnae is the only living lobe-finned fish on the planet.

The hype around unusual find, made many people rush in search of these strange inhabitants of the reservoirs. However, the caught coelacanth quickly dies, deprived natural conditions a habitat. That is why the free catch of the "resurrected" fish was banned and its main populations were taken under strict state protection.

Cross-finned coelacanth fish, like their ancient ancestors, are staunch predators. Like millions of years ago, they terrify their victims with a large number of sharp teeth and strong strong fins resembling animal paws. Under the cover of night, coelacanths lie in wait for their prey: squids and smaller fish. However, they themselves can easily become a dinner for larger predators, which are sharks.

The largest specimens of this species reach a length of about 2 m and weigh almost 100 kg. The body length of a newborn baby coelacanth is about 33 cm. Scientists believe that babies grow rather slowly, but due to their tendency to long life, they eventually grow into rather large specimens.