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The Cenozoic era The Cenozoic era - the era of new life - began about 67 million years ago and continues in our time. In this era, the modern relief, climate, atmosphere, flora and fauna, and man were formed. The Cenozoic era is divided into three periods:

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At first there was nothing. In the vast outer space, there was only a giant cloud of dust and gases. It can be assumed that from time to time spaceships with representatives of the universal mind rushed through this substance at great speed. The humanoids boredly looked out of the windows and did not even remotely guess that in a few billion years intelligence and life would arise in these places.

The gas and dust cloud eventually transformed into the solar system. And after the luminary appeared, the planets appeared. One of them was our native Earth. It happened 4.5 billion years ago. It is from those distant times that the age of the blue planet is counted, thanks to which we exist in this world.

Stages of the Earth's development

The entire history of the Earth is divided into two huge time periods. The first stage is characterized by the absence of complex living organisms. There were only single-celled bacteria that settled on our planet about 3.5 billion years ago. The second stage began about 540 million years ago. This is the time when living multicellular organisms settled on the Earth. This refers to both plants and animals. Moreover, both seas and land became their habitat. The second period continues to this day, and its crown is man.

Such huge time steps are called eons. Each eon has its own eonoteme. The latter represents a certain stage in the geological development of the planet, which is fundamentally different from other stages in the lithosphere, hydrosphere, atmosphere, and biosphere. That is, each eonoteme is strictly specific and not similar to others.

There are 4 aeons in total. Each of them, in turn, is divided into eras of the Earth, and those are divided into periods. This shows that there is a rigid gradation of large time intervals, and the geological development of the planet is taken as the basis.

catarchean

The most ancient eon is called Katarchaeus. It began 4.6 billion years ago and ended 4 billion years ago. Thus, its duration was 600 million years. Time is very ancient, so it was not divided into eras or periods. At the time of the Katarchean, there was neither the earth's crust nor the core. The planet was a cold cosmic body. The temperature in its bowels corresponded to the melting point of the substance. From above, the surface was covered with regolith, like the lunar surface in our time. The relief was almost flat due to constant powerful earthquakes. Naturally, there was no atmosphere and oxygen.

archaeus

The second aeon is called Archaea. It began 4 billion years ago and ended 2.5 billion years ago. Thus, it lasted 1.5 billion years. It is divided into 4 eras: Eoarchean, Paleoarchean, Mesoarchean and Neoarchean.

Eoarchean(4-3.6 billion years) lasted 400 million years. This is the period of formation of the earth's crust. A huge number of meteorites fell on the planet. This is the so-called Late Heavy Bombardment. It was at that time that the formation of the hydrosphere began. Water appeared on Earth. In large quantities, comets could bring it. But the oceans were still far away. There were separate reservoirs, and the temperature in them reached 90 ° Celsius. The atmosphere was characterized by a high content of carbon dioxide and a low content of nitrogen. There was no oxygen. At the end of the era, the first supercontinent of Vaalbar began to form.

paleoarchaean(3.6-3.2 billion years) lasted 400 million years. In this era, the formation of the solid core of the Earth was completed. There was a strong magnetic field. His tension was half the current. Consequently, the surface of the planet received protection from the solar wind. This period also includes primitive life forms in the form of bacteria. Their remains, which are 3.46 billion years old, have been found in Australia. Accordingly, the oxygen content in the atmosphere began to increase, due to the activity of living organisms. The formation of Vaalbar continued.

Mesoarchean(3.2-2.8 billion years) lasted 400 million years. Most notable was the existence of cyanobacteria. They are capable of photosynthesis and release oxygen. The formation of a supercontinent has been completed. By the end of the era, it had split. There was also a fall of a huge asteroid. A crater from it still exists on the territory of Greenland.

neoarchean(2.8-2.5 billion years) lasted 300 million years. This is the time of formation of the real earth's crust - tectogenesis. Bacteria continued to grow. Traces of their life are found in stromatolites, whose age is estimated at 2.7 billion years. These lime deposits were formed by huge colonies of bacteria. They are found in Australia and South Africa. Photosynthesis continued to improve.

With the end of the Archean, the eras of the Earth were continued in the Proterozoic eon. This is a period of 2.5 billion years - 540 million years ago. It is the longest of all eons on the planet.

Proterozoic

The Proterozoic is divided into 3 eras. The first is called Paleoproterozoic(2.5-1.6 billion years). It lasted 900 million years. This huge time interval is divided into 4 periods: siderium (2.5-2.3 billion years), riasium (2.3-2.05 billion years), orosirium (2.05-1.8 billion years), staterium (1.8-1.6 billion years).

siderius remarkable in the first place oxygen catastrophe. It happened 2.4 billion years ago. It is characterized by a radical change in the Earth's atmosphere. It contained a large amount of free oxygen. Prior to this, the atmosphere was dominated by carbon dioxide, hydrogen sulfide, methane and ammonia. But as a result of photosynthesis and the extinction of volcanic activity at the bottom of the oceans, oxygen filled the entire atmosphere.

Oxygen photosynthesis is characteristic of cyanobacteria, which bred on Earth 2.7 billion years ago. Prior to this, archaebacteria dominated. They do not produce oxygen during photosynthesis. In addition, at first oxygen was spent on the oxidation of rocks. In large quantities, it accumulated only in biocenoses or bacterial mats.

In the end, the moment came when the surface of the planet was oxidized. And the cyanobacteria continued to release oxygen. And it began to accumulate in the atmosphere. The process has accelerated due to the fact that the oceans also stopped absorbing this gas.

As a result, anaerobic organisms died, and they were replaced by aerobic ones, that is, those in which energy synthesis was carried out through free molecular oxygen. The planet was enveloped in the ozone layer and the greenhouse effect decreased. Accordingly, the boundaries of the biosphere expanded, and sedimentary and metamorphic rocks turned out to be completely oxidized.

All these metamorphoses led to Huron glaciation, which lasted 300 million years. It began in the siderium, and ended at the end of the riasian 2 billion years ago. The next Orosirium period notable for intensive mountain building processes. At this time, 2 huge asteroids fell on the planet. The crater from one is called Vredefort and is located in South Africa. Its diameter reaches 300 km. Second crater Sudbury is located in Canada. Its diameter is 250 km.

Last statheric period notable for the formation of the supercontinent Columbia. It included almost all the continental blocks of the planet. There was a supercontinent 1.8-1.5 billion years ago. At the same time, cells were formed that contained nuclei. That is eukaryotic cells. This was a very important stage in evolution.

The second era of the Proterozoic is called mesoproterozoic(1.6-1 billion years). Its duration was 600 million years. It is divided into 3 periods: potassium (1.6-1.4 billion years), exatium (1.4-1.2 billion years), stenium (1.2-1 billion years).

At the time of the kalimium, the supercontinent Columbia collapsed. And during the time of exatia, red multicellular algae appeared. This is indicated by a fossil find on the Canadian island of Somerset. Its age is 1.2 billion years. A new supercontinent, Rodinia, formed in the walls. It arose 1.1 billion years ago, and broke up 750 million years ago. Thus, by the end of the Mesoproterozoic, there was 1 supercontinent and 1 ocean on Earth, which was called Mirovia.

The last era of the Proterozoic is called neoproterozoic(1 billion-540 million years). It includes 3 periods: Tonian (1 billion-850 million years), Cryogeny (850-635 million years), Ediacaran (635-540 million years).

During the time of Toni, the disintegration of the supercontinent Rodinia began. This process ended in cryogeny, and the Pannotia supercontinent began to form from 8 separate pieces of land formed. Cryogeny is also characterized by complete glaciation of the planet (Snowball Earth). The ice reached the equator, and after they receded, the process of evolution of multicellular organisms sharply accelerated. The last period of the Neoproterozoic Ediacaran is notable for the appearance of soft-bodied creatures. These multicellular animals are called vendobionts. They were branching tubular structures. This ecosystem is considered the oldest.

Life on Earth originated in the ocean

Phanerozoic

Approximately 540 million years ago, the time of the 4th and last eon, the Phanerozoic, began. There are 3 very important eras of the Earth here. The first is called Paleozoic(540-252 million years). It lasted 288 million years. It is divided into 6 periods: Cambrian (540-480 Ma), Ordovician (485-443 Ma), Silurian (443-419 Ma), Devonian (419-350 Ma), Carboniferous (359-299 Ma) and Permian (299-252 Ma).

Cambrian considered the lifetime of trilobites. These are marine animals that look like crustaceans. Together with them, jellyfish, sponges and worms lived in the seas. This abundance of living beings is called Cambrian explosion. That is, there was nothing like this before, and suddenly it suddenly appeared. Most likely, it was in the Cambrian that mineral skeletons began to emerge. Previously, the living world had soft bodies. They, of course, did not survive. Therefore, complex multicellular organisms of more ancient eras cannot be detected.

The Paleozoic is notable for the rapid spread of organisms with hard skeletons. From vertebrates, fish, reptiles and amphibians appeared. In the plant world, algae predominated at first. During Silurian plants began to colonize the land. At first Devonian swampy shores are overgrown with primitive representatives of the flora. These were psilophytes and pteridophytes. Plants reproduced by spores carried by the wind. Plant shoots developed on tuberous or creeping rhizomes.

Plants began to develop land in the Silurian period

There were scorpions, spiders. The real giant was the Meganevra dragonfly. Its wingspan reached 75 cm. Acanthodes are considered the oldest bony fish. They lived during the Silurian period. Their bodies were covered with dense diamond-shaped scales. IN carbon, which is also called the Carboniferous period, the most diverse vegetation flourished on the shores of the lagoons and in countless swamps. It was its remains that served as the basis for the formation of coal.

This time is also characterized by the beginning of the formation of the supercontinent Pangea. It was fully formed in the Permian period. And it broke up 200 million years ago into 2 continents. These are the northern continent of Laurasia and the southern continent of Gondwana. Subsequently, Laurasia split, and Eurasia and North America were formed. And South America, Africa, Australia and Antarctica arose from Gondwana.

On Permian there were frequent climate changes. Dry times gave way to wet ones. At this time, lush vegetation appeared on the banks. Typical plants were cordaites, calamites, tree and seed ferns. Mesosaurus lizards appeared in the water. Their length reached 70 cm. But by the end of the Permian period, early reptiles died out and gave way to more developed vertebrates. Thus, in the Paleozoic, life reliably and densely settled on the blue planet.

Of particular interest to scientists are the following eras of the Earth. 252 million years ago mesozoic. It lasted 186 million years and ended 66 million years ago. It consisted of 3 periods: Triassic (252-201 million years), Jurassic (201-145 million years), Cretaceous (145-66 million years).

The border between the Permian and the Triassic period is characterized by the mass extinction of animals. 96% of marine species and 70% of terrestrial vertebrates died. A very strong blow was dealt to the biosphere, and it took a very long time to recover. And it all ended with the appearance of dinosaurs, pterosaurs and ichthyosaurs. These sea and land animals were of enormous size.

But the main tectonic event of those years - the collapse of Pangea. A single supercontinent, as already mentioned, was divided into 2 continents, and then broke up into those continents that we know now. The Indian subcontinent also broke away. Subsequently, it connected with the Asian plate, but the collision was so violent that the Himalayas were created.

Such nature was in the early Cretaceous period

The Mesozoic is notable for being considered the warmest period of the Phanerozoic eon.. This is the time of global warming. It began in the Triassic and ended at the end of the Cretaceous. For 180 million years, even in the Arctic there were no stable pack glaciers. Heat spread evenly throughout the planet. At the equator, the average annual temperature corresponded to 25-30 ° Celsius. The polar regions were characterized by a moderately cool climate. In the first half of the Mesozoic, the climate was dry, while the second half was characterized by humid. It was at this time that the equatorial climatic zone was formed.

In the animal world, mammals arose from a subclass of reptiles. This was due to the improvement of the nervous system and brain. The limbs moved from the sides under the body, the reproductive organs became more perfect. They ensured the development of the embryo in the mother's body, followed by feeding it with milk. A woolen cover appeared, blood circulation and metabolism improved. The first mammals appeared in the Triassic, but they could not compete with dinosaurs. Therefore, for more than 100 million years, they occupied a dominant position in the ecosystem.

The last era is Cenozoic(beginning 66 million years ago). This is the current geological period. That is, we all live in the Cenozoic. It is divided into 3 periods: the Paleogene (66-23 million years), the Neogene (23-2.6 million years) and the modern anthropogen or Quaternary period, which began 2.6 million years ago.

There are 2 major events in the Cenozoic. The mass extinction of dinosaurs 65 million years ago and the general cooling on the planet. The death of animals is associated with the fall of a huge asteroid with a high content of iridium. The diameter of the cosmic body reached 10 km. This resulted in the formation of a crater. Chicxulub with a diameter of 180 km. It is located on the Yucatan Peninsula in Central America.

Earth's surface 65 million years ago

After the fall, there was an explosion of great force. Dust rose into the atmosphere and covered the planet from the sun's rays. The average temperature dropped by 15°. Dust hung in the air for a whole year, which led to a sharp cooling. And since the Earth was inhabited by large heat-loving animals, they died out. Only small representatives of the fauna remained. It was they who became the ancestors of the modern animal world. This theory is based on iridium. The age of its layer in geological deposits corresponds exactly to 65 million years.

During the Cenozoic, the continents diverged. Each of them formed its own unique flora and fauna. The diversity of marine, flying and land animals has increased significantly in comparison with the Paleozoic. They have become much more advanced, and mammals have taken the dominant position on the planet. In the plant world, higher angiosperms appeared. This is the presence of a flower and an ovule. There were also cereal crops.

The most important thing in the last era is anthropogen or Quaternary, which began 2.6 million years ago. It consists of 2 epochs: the Pleistocene (2.6 million years - 11.7 thousand years) and the Holocene (11.7 thousand years - our time). During the Pleistocene era mammoths, cave lions and bears, marsupial lions, saber-toothed cats and many other animal species that became extinct at the end of the era lived on Earth. 300 thousand years ago, a man appeared on the blue planet. It is believed that the first Cro-Magnons chose for themselves the eastern regions of Africa. At the same time, Neanderthals lived on the Iberian Peninsula.

Notable for the Pleistocene and Ice Ages. For a whole 2 million years, very cold and warm periods of time alternated on Earth. Over the past 800 thousand years, there have been 8 ice ages with an average duration of 40 thousand years. In cold times, glaciers advanced on the continents, and receded in interglacials. At the same time, the level of the World Ocean was rising. About 12 thousand years ago, already in the Holocene, another ice age ended. The climate became warm and humid. Thanks to this, humanity has settled all over the planet.

The Holocene is an interglacial. It has been going on for 12 thousand years. Human civilization has been developing for the last 7 thousand years. The world has changed in many ways. Significant transformations, thanks to the activities of people, have undergone flora and fauna. Today, many animal species are on the verge of extinction. Man has long considered himself the ruler of the world, but the eras of the Earth have not disappeared. Time continues its steady course, and the blue planet conscientiously revolves around the Sun. In a word, life goes on, but what will happen next - the future will show.

The article was written by Vitaly Shipunov

Hello! In this article I want to tell you about the geochronological column. This is a column of periods of the Earth's development. And also more about each era, thanks to which you can draw a picture of the formation of the Earth throughout its history. What types of life first appeared, how did they change, and how much did it take.

The geological history of the Earth is divided into large intervals - eras, eras are divided into periods, periods are divided into epochs. Such a division was associated with events that took place on. The change in the abiotic environment influenced the evolution of the organic world on Earth.

Geological eras of the Earth, or geochronological scale:

And now about everything in more detail:

Designations:
eras;
periods;
Epochs.

1. Catharchean era (from the creation of the Earth, about 5 billion years ago, to the origin of life);

2. Archean era , the most ancient era (3.5 billion - 1.9 billion years ago);

3. Proterozoic era (1.9 billion - 570 million years ago);

Archean and Proterozoic are still combined into Precambrian. The Precambrian covers the largest part of geological time. Formed, areas of land and sea, active volcanic activity took place. Shields of all continents were formed from Precambrian rocks. Traces of life are usually rare.

4. Palaeozoic (570 million - 225 million years ago) with such periods :

Cambrian period(from the Latin name for Wales)(570 million - 480 million years ago);

The transition to the Cambrian is marked by the unexpected appearance of a huge number of fossils. This is a sign of the beginning of the Paleozoic era. Marine life flourished in numerous shallow seas. Trilobites were especially widespread.

Ordovician period(from the British Ordovician tribe)(480 million - 420 million years ago);

On a significant part of the Earth it was soft, most of the surface was still covered by the sea. The accumulation of sedimentary rocks continued, mountain building took place. There were reef builders. An abundance of corals, sponges and molluscs has been noted.

Silurian (from the British Silur tribe)(420 million - 400 million years ago);

Dramatic events in the history of the Earth began with the development of jawless fish (the first vertebrates), which appeared in the Ordovician. Another significant event was the appearance in the late Silurian of the first terrestrial.

Devonian (from Devonshire in England)(400 million - 320 million years ago);

In the early Devonian, mountain building movements reached their peak, but basically it was a period of spasmodic development. The first seed plants settled on land. A great variety and number of fish-like species was noted, the first terrestrial animals- amphibians.

Carboniferous or Carboniferous period (from the abundance of coal in the seams) (320 million - 270 million years ago);

Mountain building, folding, and erosion continued. In North America, swampy forests and river deltas were flooded, and large carbonaceous deposits formed. The southern continents were covered by glaciation. Insects spread rapidly, the first reptiles appeared.

Permian period (from the Russian city of Perm)(270 million - 225 million years ago);

A large part of Pangea - the supercontinent that united everything - was dominated by conditions. Reptiles spread widely, modern insects evolved. A new terrestrial flora developed, including conifers. Several marine species have disappeared.

5. Mesozoic era (225 million - 70 million years ago) with such periods:

Triassic (from the tripartite division of the period proposed in Germany)(225 million - 185 million years ago);

With the advent of the Mesozoic era, Pangea began to disintegrate. On land, the dominance of conifers was established. Diversity among reptiles is noted, the first dinosaurs and giant marine reptiles appeared. Primitive mammals evolved.

Jurassic period(from mountains in Europe)(185 million - 140 million years ago);

Significant volcanic activity was associated with the formation of the Atlantic Ocean. Dinosaurs dominated the land, flying reptiles and primitive birds conquered the air ocean. There are traces of the first flowering plants.

Cretaceous period (from the word "chalk")(140 million - 70 million years ago);

During the maximum expansion of the seas, chalk deposits occurred, especially in Britain. The dominance of dinosaurs continued until the extinction of them and other species at the end of the period.

6. Cenozoic era (70 million years ago - up to our time) with such periods And epochs:

Paleogene period (70 million - 25 million years ago);

— Paleocene epoch ("the oldest part of the new epoch")(70 million - 54 million years ago);
— Eocene epoch ("dawn of a new era")(54 million - 38 million years ago);
— Oligocene era ("not very new")(38 million - 25 million years ago);

Neogene period (25 million - 1 million years ago);

— Miocene epoch ("comparatively new")(25 million - 8 million years ago);
— Pliocene epoch ("very new")(8 million - 1 million years ago);

The Paleocene and Neocene periods are still combined into the Tertiary period. With the advent of the Cenozoic era (new life), there is an abrupt spread of mammals. Many large species have evolved, although many have become extinct. There has been a sharp increase in the number of flowering plants. With the cooling of the climate, herbaceous plants appeared. There has been a significant uplift.

Quaternary period (1 million - our time);

— Pleistocene era ("newest")(1 million - 20 thousand years ago);

— Holocene epoch(“a completely new era”) (20 thousand years ago - our time).

This is the last geological period that includes the present. Four major glaciations alternated with warming periods. The number of mammals has increased; they have adapted to. There was a formation of man - the future ruler of the Earth.

There are also other ways of dividing eras, epochs, periods, eons are added to them, and some epochs are still divided, like in this table, for example.

But this table is more complicated, the confusing dating of some eras is purely chronological, not based on stratigraphy. Stratigraphy is the science of determining the relative geologic age of sedimentary rocks, subdividing rock strata, and correlating different geological formations.

Such a division, of course, is relative, since there was no sharp distinction between today and tomorrow in these divisions.

But still, at the turn of neighboring eras and periods, significant geological transformations mainly took place: the processes of formation of mountains, the redistribution of seas, changing of the climate etc.

Each subsection was characterized, of course, by the originality of flora and fauna.

, And can be found in the same section.

Thus, these are the main eras of the Earth, on which all scientists rely 🙂

The notion of how life originated in the ancient eras of the Earth give us the fossil remains of organisms, but they are distributed in separate geological periods extremely uneven.

Geological periods

The era of the ancient life of the Earth includes 3 stages of the evolution of flora and fauna.

Archean era

Archean era- the oldest era in the history of existence. Its beginning takes a count of about 4 billion years ago. And the duration is 1 billion years. This is the beginning of the formation of the earth's crust as a result of the activity of volcanoes and air masses, sharp changes in temperature and pressure. There is a process of destruction of the primary mountains and the formation of sedimentary rocks.

The most ancient Archeozoic layers of the earth's crust are represented by highly altered, otherwise metamorphosed rocks, and therefore they do not contain noticeable remains of organisms.
But on this basis it is absolutely wrong to consider the archaeozoic a lifeless era: in the archaeozoic there were not only bacteria and algae, but also more complex organisms.

Proterozoic era

The first reliable traces of life in the form of extremely rare finds and poor quality preservation are found in Proterozoic, otherwise - the era of "primary life". The duration of the Proterozoic era is about 2 million years

Traces of crawling found in Proterozoic rocks annelids, sponge needles, shells of the simplest forms of brachiopods, arthropod remains.

Brachiopods, distinguished by an exceptional variety of forms, were widespread in the most ancient seas. They are found in the deposits of many periods, especially the next, the Paleozoic era.

Shell of the brachiopod "Horistites Moskmenzis" (ventral valve)

Only certain species of brachiopods have survived to this day. Most of the brachiopods had a shell with unequal valves: the ventral one, on which they lie or are attached to the seabed with the help of a "leg", was usually larger than the dorsal one. On this basis, in general, it is not difficult to recognize brachiopods.

An insignificant amount of fossil remains in the Proterozoic deposits is explained by the destruction of most of them as a result of a change (metamorphization) of the containing rock.

To judge how much life was represented in the Proterozoic, deposits help limestone, which then turned into marble. Limestones obviously owe their origin to a special type of bacteria that secreted carbonic lime.

The presence of interlayers in the Proterozoic deposits of Karelia shungite, similar to anthracite coal, suggests that the initial material for its formation was the accumulation of algae and other organic residues.

In this distant time, the most ancient dry land was still not lifeless. In the vast expanses of still desert primary continents, bacteria settled. With the participation of these simple organisms, the weathering and loosening of the rocks that made up the most ancient earth's crust took place.

According to the Russian academician L. S. Berga(1876-1950), who studied how life originated in the ancient eras of the Earth, at that time soils had already begun to form - the basis for the further development of vegetation cover.

Palaeozoic

Deposits next in time, Paleozoic era, otherwise, the era of "ancient life", which began about 600 million years ago, differs sharply from the Proterozoic in the abundance and variety of forms even in the most ancient, Cambrian period.

Based on the study of the remains of organisms, it is possible to restore the following picture of the development of the organic world, characteristic of this era.

There are six periods of the Paleozoic era:

Cambrian period

Cambrian period was described for the first time in England, the county of Cambria, from where its name came from. During this period, all life was connected with water. These are red and blue-green algae, limestone algae. Algae released free oxygen, which made it possible for the development of organisms that consume it.

Careful study of blue-green Cambrian clays, which are clearly visible in the deep sections of the river valleys near St. Petersburg and especially in the coastal regions of Estonia, made it possible to establish in them (through a microscope) the presence plant spores.

This definitely suggests that some species that have existed in water since the earliest times of the development of life on our planet moved to land about 500 million years ago.

Among the organisms that inhabited the oldest Cambrian reservoirs, invertebrates were exceptionally widespread. Of the invertebrates, except for the smallest protozoa - rhizopods, were widely represented worms, brachiopods and arthropods.

Of the arthropods, these are primarily various insects, especially butterflies, beetles, flies, dragonflies. They appear much later. To the same type of animal world, in addition to insects, also belong arachnids and centipedes.

Among the most ancient arthropods, there were especially many trilobites, similar to modern wood lice, only much larger than them (up to 70 centimeters), and crustaceans, which sometimes reached impressive sizes.

In the body of a trilobite, three lobes are clearly distinguished, it is not for nothing that it is called so: in translation from the ancient Greek “trilobos” - three-lobed. Trilobites not only crawled along the bottom and burrowed into the silt, but could also swim.

Among the trilobites, generally medium-sized forms prevailed.
By definition of geologists, trilobites - "guiding fossils" - are characteristic of many deposits of the Paleozoic.

Fossils that prevail at a given geological time are called guiding fossils. From guide fossils, the age of the deposits in which they are found is usually easily determined. Trilobites reached their peak during the Ordovician and Silurian periods. They disappeared at the end of the Paleozoic era.

Ordovician period

Ordovician period characterized by a warmer and milder climate, as evidenced by the presence of limestone, shale and sandstone in the rock deposits. At this time, the area of ​​the seas increases significantly.

This promotes the reproduction of large trilobites, from 50 to 70 cm long. Appear in the seas sea ​​sponges, clams, and the first corals.

Silurian

What did the Earth look like? Silurian? What changes have taken place on the primeval continents? Judging by the imprints on clay and other stone material, one can definitely say that at the end of the period, the first terrestrial vegetation appeared on the shores of water bodies.

The first plants of the Silurian period

These were small leafy plants, resembling rather sea brown algae, having neither roots nor leaves. The role of the leaves was played by green successively branching stems.

The scientific name of these ancient progenitors of all terrestrial plants (psilophytes, otherwise - "naked plants", that is, plants without leaves) well conveys their distinctive features. (Translated from the ancient Greek "psilos" - bald, naked, and "phytos" - the trunk). Their roots were also undeveloped. Psilophytes grew on swampy marshy soils. An imprint in the rock (right) and a restored plant (left).

The inhabitants of the reservoirs of the Silurian period

From inhabitants maritime Silurian reservoirs It should be noted, apart from trilobites, corals And echinoderms - sea ​​lilies, sea urchins and stars.

Sea lilies, the remains of which were found in sediments, looked very little like predatory animals. Sea lily "Acanthocrinus-rex" means "spiny lily-king" in translation. The first word is formed from two Greek words: "acantha" - a prickly plant and "krinon" - a lily, the second Latin word "rex" - a king.

A huge number of species were represented by cephalopods and especially brachiopods. In addition to cephalopods, which had an inner shell, like belemnites, cephalopods with an external shell were widely used in the most ancient periods of the life of the Earth.

The shape of the shell was straight and curved in a spiral. The shell was successively divided into chambers. The body of the mollusk was placed in the largest outer chamber, the rest were filled with gas. A tube passed through the chambers - a siphon, which allowed the mollusk to regulate the amount of gas and, depending on this, float or sink to the bottom of the reservoir.

At present, of such cephalopods, only one ship with a coiled shell has been preserved. ship, or nautilus, which is the same thing, translated from Latin - an inhabitant of the warm sea.

The shells of some Silurian cephalopods, such as orthoceras (translated from the ancient Greek “straight horn”: from the words “orthoe” - straight and “keras” - horn), reached gigantic sizes and looked more like a straight two-meter pillar than a horn.

Limestones in which orthoceratites occur are called orthoceratite limestones. Square limestone slabs were widely used in pre-revolutionary St. Petersburg for sidewalks, and characteristic cuts of orthoceratite shells were often clearly visible on them.

A remarkable event of the Silurian time was the appearance in fresh and brackish water bodies of clumsy " armored fish”, which had an external bone shell and an unossified internal skeleton.

Their spinal column was answered by a cartilaginous cord - a chord. The shells did not have jaws and paired fins. They were poor swimmers and therefore stuck more to the bottom; their food was silt and small organisms.

The armored fish pterichthys was generally a poor swimmer and led a natural lifestyle.

It can be assumed that bothriolepis was already much more mobile than pterychthys.

Sea predators of the Silurian period

In later deposits, there are already remains marine predators close to sharks. Of these lower fish, which also had a cartilaginous skeleton, only teeth were preserved. Judging by the size of the teeth, for example, from the deposits of the Carboniferous age of the Moscow region, it can be concluded that these predators reached considerable sizes.

In the development of the animal world of our planet, the Silurian period is interesting not only because distant ancestors of fish appear in its reservoirs. At the same time, another equally important event took place: representatives of arachnids got out of the water onto land, among them ancient scorpions, still very close to crustaceans.

On the right, above, a predator armed with strange claws - pterygotus, reaching 3 meters, glory - eurypterus - up to 1 meter long.

Devonian

The land - the arena of the future life - gradually takes on new features, especially characteristic of the next, Devonian period. At this time, already woody vegetation appears, first in the form of low-growing shrubs and small trees, and then larger ones. Among the Devonian vegetation, we will meet well-known ferns, other plants will remind us of an elegant horsetail tree and green cords of club mosses, but not creeping along the ground, but proudly rising up.

Fern-like plants also appear in later Devonian deposits, which reproduced not by spores, but by seeds. These are seed ferns, occupying a transitional position between spore and seed plants.

Fauna of the Devonian period

Animal world seas Devonian period rich in brachiopods, corals and sea lilies; trilobites begin to play a secondary role.

Among the cephalopods, new forms appear, only not with a straight shell, like in Orthoceras, but with a spirally twisted one. They are called ammonites. They got their name from the Egyptian sun god Ammon, near the ruins of whose temple in Libya (in Africa) these characteristic fossils were first discovered.

In general appearance, they are difficult to confuse with other fossils, but at the same time it is necessary to warn young geologists about how difficult it is to identify individual types of ammonites, the total number of which is not hundreds, but thousands.

Ammonites reached a particularly magnificent flourishing in the next, Mesozoic era. .

Significant development in the Devonian time received fish. Armored fish have shortened their bony shells, making them more mobile.

Some armored fish, such as the nine-meter giant dinichthys, were terrible predators (in Greek, “deinos” is terrible, terrible, and “ichthys” is fish).

The nine-meter dinichthys obviously posed a great threat to the inhabitants of the reservoirs.

In the Devonian reservoirs, there were also lobe-finned fish, from which the lungfish originated. This name is explained by the structural features of the paired fins: they are narrow and, in addition, sit on an axis covered with scales. In this feature, the lobe-finned fish differ, for example, from pike perch, perch and other bony fish called ray-finned fish.

The lobe-finned ancestors of bony fish, which appeared much later - at the end of the Triassic.
We would not even have an idea of ​​how the loach-finned fish actually looked like, which lived at least 300 million years ago, if it were not for the successful catches of the rarest specimens of their modern generation off the coast of South Africa in the middle of the 20th century.

They live, obviously, at considerable depths, which is why they come across so rarely to fishermen. The caught species was named coelacanth. It reached 1.5 meters in length.
In their organization, lungfish are close to the cross-finned fish. They have lungs corresponding to the swim bladder of a fish.

In their organization, lungfish are close to the cross-finned fish. They have lungs corresponding to the swim bladder of a fish.

How unusual the crossopterygians looked can be judged by a specimen, a coelacanth, caught in 1952 off the Comoros, west of the island of Madagascar. This fish, 1.5 liters long, weighed about 50 kg.

A descendant of ancient lungfish - the Australian ceratodus (translated from ancient Greek - horned tooth) - reaches two meters. He lives in drying up reservoirs and, as long as there is water in them, he breathes with gills, like all fish, but when the reservoir begins to dry out, he switches to pulmonary respiration.

Its respiratory organs are the swim bladder, which has a cellular structure and is equipped with numerous blood vessels. In addition to ceratodus, two more species of lungfish are now known. One of them lives in Africa, and the other - in South America.

Transition of vertebrates from water to land

Table of transformation of amphibians.

The first picture shows the oldest cartilaginous fish, diplocanthus (1). Below it is a primitive crossopterygian eusthenopteron (2), a putative, transitional form (3) is shown below. In a huge amphibious eogyrinus (about 4.5 m long), the limbs are still very weak (4), and only as they master the land lifestyle do they become a reliable support, for example, for overweight eriops, about 1.5 m long (5).

This table helps to understand how, as a result of a gradual change in the organs of movement (and respiration), aquatic organisms moved to land, how the fin of a fish was transformed into the limb of amphibians (4), and then reptiles (5). Along with this, the spine and skull of the animal change.

The appearance of the first wingless insects and terrestrial vertebrates belongs to the Devonian period. Hence, it can be assumed that it was at this time, and possibly even somewhat earlier, that the transition of vertebrates from water to land took place.

It was carried out through such fish, in which the swim bladder was changed, like that of lungfish, and the limbs, similar to fins, gradually turned into five-fingered ones, adapted to a terrestrial lifestyle.

Metopoposaurus still struggled to get out on land.

Therefore, the closest ancestors of the first terrestrial animals should be considered not lungfish, but lobe-finned fish, adapted to breathing atmospheric air as a result of periodic drying up of tropical reservoirs.

The connecting link between terrestrial vertebrates and the lobe-feathered ones is the ancient amphibians, or amphibians, united by the common name stegocephals. Translated from ancient Greek, stegocephaly means “covered heads”: from the words “stege” - roof and “kefale” - head. This name is given because the roof of the skull is an oversized shell of bones closely adjacent to each other.

There are five holes in the skull of the stegocephalus: two pairs of holes - eye and nasal, and one - for the parietal eye. In appearance, stegocephals somewhat resembled salamanders and often reached considerable sizes. They lived in swampy areas.

The remains of stegocephalians were sometimes found in the hollows of tree trunks, where they apparently hid from daylight. In the larval state, they breathed with gills, like modern amphibians.

Stegocephals found especially favorable conditions for their development in the next Carboniferous period.

Carboniferous period

Warm and humid climate, especially in the first half carboniferous period, favored the lush flourishing of terrestrial vegetation. Unseen coal forests, of course, were quite unlike modern ones.

Among those plants that about 275 million years ago settled in the swampy swampy expanses, giant tree-like horsetails and club mosses clearly stood out in their characteristic features.

Of tree-like horsetails, calamites were widely used, and of club mosses, giant lepidodendrons and graceful sigillaria, somewhat inferior to them in size, were widely used.

Well-preserved remnants of vegetation are often found in coal seams and overlying rocks, not only in the form of clear imprints of leaves and tree bark, but also whole stumps with roots and huge trunks turned into coal.

Based on these fossil remains, one can not only restore the general appearance of the plant, but also get acquainted with its internal structure, which is clearly visible under a microscope in the thinnest sections of the trunk, like a sheet of paper. Calamity derives its name from the Latin word "kalamus" - reed, reed.

Slender, hollow inside the trunks of calamites, ribbed and with transverse constrictions, like those of the well-known horsetails, rose in slender columns 20-30 meters from the ground.

Small narrow leaves, collected in rosettes on short stems, gave, perhaps, a certain resemblance to calamite with larch of the Siberian taiga, transparent in its elegant dress.

Nowadays, horsetails - field and forest - are distributed throughout the globe, except for Australia. In comparison with their distant ancestors, they seem to be miserable dwarfs, who, moreover, especially the field horsetail, enjoy a bad reputation with the farmer.

Horsetail is the worst weed, which is difficult to fight, as its rhizome goes deep into the ground and constantly gives new shoots.

Large species of horsetail - up to 10 meters in height are currently preserved only in the tropical forests of South America. However, these giants can only grow by leaning against neighboring trees, since they are only 2-3 centimeters across.
Lepidodendrons and sigillaria occupied a prominent place among the Carboniferous vegetation.

Although in appearance they did not look like modern club mosses, they nevertheless resembled them in one of their characteristic features. The powerful trunks of lepidodendrons, reaching 40 meters in height, with a diameter of up to two meters, were covered with a distinct pattern of fallen leaves.

These leaves, while the plant was still young, sat on the trunk in the same way as its small green scales - leaves - sit on the club moss. As the tree grows, the leaves age and fall off. From these scaly leaves, the giants of the coal forests - lepidodendrons, otherwise - "scaly trees" (from the Greek words: "lepis" - scales and "dendron" - tree) got their name.

Traces of fallen leaves on the bark of sigillaria had a slightly different shape. They differed from lepidodendrons in their smaller height and greater slenderness of the trunk, which branched only at the very top and ended in two huge bunches of hard leaves, each meter long.

Acquaintance with the Carboniferous vegetation will be incomplete if we do not also mention cordaites, which are close to conifers in terms of wood structure. These were tall (up to 30 meters), but relatively thin-stemmed trees.

Cordaites derive their name from the Latin elephant "cor" - heart, since the seed of the plant had a heart-shaped shape. These beautiful trees were crowned with a lush crown of ribbon-like leaves (up to 1 meter in length).

Judging by the structure of the wood, the trunks of the coal giants still did not have the strength that is inherent in the bulk of modern trees. Their bark was much stronger than wood, hence the general fragility of the plant, weak resistance to fracture.

Strong winds and especially storms broke trees, felled huge forests, and new lush growth again grew from the swampy soil to replace them ... The felled wood served as the source material from which powerful layers of coal were later formed.

Lepidodendrons, otherwise - scaly trees, reached enormous sizes.

It is not correct to attribute the formation of coal only to the Carboniferous period, since coals also occur in other geological systems.

For example, the oldest Donetsk coal basin was formed in the Carboniferous time. The Karaganda basin is the same age as it.

As for the largest Kuznetsk basin, it only in an insignificant part belongs to the Carboniferous system, and mainly to the Permian and Jurassic systems.

One of the largest basins - "Zapolyarnaya Kochegarka" - the richest Pechora basin, was also formed mainly in the Permian and, to a lesser extent, in the Carboniferous.

Flora and fauna of the Carboniferous period

For marine sediments carboniferous period representatives of the simplest animals from the class rhizopods. The most typical were fusulins (from the Latin word "fuzus" - "spindle") and schwagerins, which served as the source material for the formation of strata of fusulin and schwagerin limestones.

Carboniferous rhizomes - fuzulina (1) and schwagerina (2) are enlarged 16 times.

Elongated, like grains of wheat, fuzulins and almost spherical schwagerins are clearly visible on the limestones of the same name. Corals and brachiopods have been luxuriantly developed, giving many guiding forms.

The most widespread were the genus productus (translated from Latin - “stretched”) and spirifer (translated from the same language - “carrying a spiral”, which supported the soft “legs” of the animal).

The trilobites that dominated in previous periods are much less common, but on land, other representatives of arthropods - long-legged spiders, scorpions, huge centipedes (up to 75 centimeters in length) and especially giant-shaped insects, similar to dragonflies, with a span of "wings" up to 75 centimeters! The largest modern butterflies in New Guinea and Australia reach a wingspan of 26 centimeters.

The oldest coal dragonfly seems to be an exorbitant giant compared to the modern one.

Judging by the fossil remains, sharks have noticeably multiplied in the seas.
Amphibians, firmly entrenched on land in the Carboniferous, go through a further path of development. The dryness of the climate, which increased at the end of the Carboniferous period, gradually forces the ancient amphibians to move away from the aquatic lifestyle and move mainly to a terrestrial existence.

These organisms, transitional to a new way of life, already laid their eggs on land, and did not spawn in the water, like amphibians. The offspring hatched from the eggs acquired such features that sharply distinguished it from the progenitors.

The body was covered, like a shell, with scale-like outgrowths of the skin, protecting the body from moisture loss through evaporation. So reptiles, or reptiles, separated from amphibians (amphibians). In the next, Mesozoic era, they conquered land, water and air.

Permian period

The last period of the Paleozoic - Permian- in duration was much shorter than the Carboniferous. It should be noted, in addition, the great changes that have taken place on the ancient geographical map of the world - land, as confirmed by geological research, receives a significant predominance over the sea.

Plants of the Permian period

The climate of the northern continents of the Upper Permian was dry and sharply continental. Sandy deserts are widely distributed in places, as evidenced by the composition and reddish hue of the rocks that make up the Permian suite.

This time was marked by the gradual extinction of the giants of the coal forests, the development of plants close to conifers, and the appearance of cycads and ginkgos, which became widespread in the Mesozoic.

Cycad plants have a spherical and tuberous stem immersed in the soil, or, conversely, a powerful columnar trunk up to 20 meters high, with a lush rosette of large pinnate leaves. In appearance, cycad plants resemble the modern sago palm of tropical forests in the Old and New Worlds.

Sometimes they form impenetrable thickets, especially on the flooded banks of the rivers of New Guinea and the Malay Archipelago (Greater Sunda Islands, Lesser Sunda, Moluccas and Philippine). Nutritious flour and cereals (sago) are made from the soft core of the palm tree, which contains starch.

Sago bread and porridge are the daily food of millions of inhabitants of the Malay Archipelago. The sago palm is widely used in residential construction and for household products.

Another very peculiar plant - ginkgo is also interesting because in the wild it has survived only in some places in southern China. Ginkgo has been carefully bred near Buddhist temples since time immemorial.

Ginkgo was brought to Europe in the middle of the 18th century. Now it is found in park culture in many places, including ours on the Black Sea coast. Ginkgo is a large tree up to 30-40 meters in height and up to two meters thick, in general it resembles a poplar, and in its youth it looks more like some conifers.

The leaves are petiolate, like those of aspen, have a fan-shaped plate with fan-shaped venation without transverse bridges and an incision in the middle. Leaves fall in winter. The fruit, a fragrant drupe like a cherry, is edible in the same way as the seeds. In Europe and Siberia, ginkgo disappeared during the Ice Age.

Cordaites, conifers, cycads and ginkgo belong to the group of gymnosperms (since their seeds lie open).

Angiosperms - monocotyledonous and dicotyledonous - appear somewhat later.

Fauna of the Permian period

Among the aquatic organisms that inhabited the Permian seas, ammonites stood out noticeably. Many groups of marine invertebrates, such as trilobites, some corals, and most brachiopods, have become extinct.

Permian period characterized by the development of reptiles. The so-called animal-like lizards deserve special attention. Although they had some features characteristic of mammals, such as teeth and skeletal features, they still retained a primitive structure that brings them closer to stegocephals (from which reptiles originated).

The animal-like Permian lizards differed in significant sizes. The sedentary herbivorous pareiasaurus reached two and a half meters in length, and the formidable predator with the teeth of a tiger, otherwise the "animal-toothed lizard" - foreigners, was even larger - about three meters.

Pareiasaurus, translated from ancient Greek, means “cheeky lizard”: from the words “pareia” - cheek and “sauros” - lizard, lizard; the animal-toothed lizard of foreigners is named so in memory of the famous geologist - prof. A. A. Inostrantseva (1843-1919).

The richest finds of the remains of these animals from the ancient life of the Earth are associated with the name of the enthusiastic geologist prof. V. P. Amalitsky(1860-1917). This persistent researcher, not receiving the necessary support from the treasury, nevertheless achieved remarkable results in his work. Instead of a well-deserved summer vacation, he, along with his wife, who shared all the hardships with him, went in a boat with two rowers in search of the remains of animal-like lizards.

Persistently, for four years he conducted his research on the Sukhona, the Northern Dvina and other rivers. Finally, he managed to make discoveries of exceptional value for world science on the Northern Dvina, not far from the town of Kotlas.

Here, in the coastal cliff of the river, in thick lentils of sand and sandstone, among striped rukhlyak, concretions of bones of ancient animals (concretions - stone accumulations) were found. Gatherings of only one year of work of geologists took two freight cars during transportation.

Subsequent developments of these bone-bearing accumulations further enriched the information about Permian reptiles.

Location of Perm pangolins discovered by professor V. P. Amalitsky in 1897. The right bank of the Malaya Severnaya Dvina River near the village of Efimovka, near the town of Kotlas.

The richest collections taken out from here amount to tens of tons, and the skeletons collected from them represent the richest collection in the Paleontological Museum of the Academy of Sciences, which has no equal in any museum in the world.

Among the ancient animal-like Permian reptiles, the original three-meter predator Dimetrodon stood out, otherwise it was “two-dimensional” in length and height (from the ancient Greek words: “di” - twice and “metron” - measure).

Its characteristic feature is the unusually long processes of the vertebrae, forming a high ridge (up to 80 centimeters) on the back of the animal, which were apparently connected by a skin membrane. In addition to predators, this group of reptiles also included plant- or mollusk-eating forms, also of very considerable size. The fact that they ate mollusks can be judged by the arrangement of teeth suitable for crushing and grinding shells. (No ratings yet)