The Devonian period of the Paleozoic era: characteristics, major events, animals and plants
The Devonian period is the fourth period of the Paleozoic era in the geological history of our planet. This is a time of rapid development of the biological system and serious cataclysms. The events that took place in those times had an extraordinary influence on the development of the subsequent mortal life. This is the period of formation of the soil, the development of new forms and types of living beings, the dynamic conquest of land by them, the beginning of the formation of humus and mineral deposits.
For the first time this term was singled out by scientists - the Englishmen Adam Sedgwick and Roderick Murchison - in 1839 in the county of Devonshire, hence the name of the period. With the help of radiological studies, the times (420–350 million years ago) and the duration of the Devonian period, which becomes about 60 million years, are established.In 1845, the German scientists Zanberger brothers, having divided the longlines in the Ardenes and the Rhine Mountains, made up the first division of the system. At the moment, Devon is divided into three periods and seven tiers, which have undergone some changes since the first experiments.
Fossils are indicators of the era
Paleontology - the science of vegetation, wildlife, geology of past periods. The remains extracted from the rock layers of their time serve as an indicator of their era. Fossil fossils help to make a correct picture of the climate, the conditions of existence of organisms, their evolution and adaptation to the natural environment, which is constantly changing under the influence of cataclysms. The Devonian period is the time of the first ferns, the first terrestrial animals, spore plants, bivalves, trilobites, fish, corals, the first terrestrial insects and amphibians.
The geological period of the Devonian is characterized as the era of land dominance, which has risen due to the regress of the sea. After a series of earthquakes and volcanic eruptions of the early period, the seas in the folds of the Ural-Tien-Shan,The Cordillera and Tasmanian geosynclines, the troughs in which were gradually filled with sand and pebbles, which were formed in the process of smearing land. As a result, huge areas of red sandstone were formed. Multiple rivers that endure sediments to the seas have formed swampy deltas, very convenient for life and development of various forms and types of living beings. The territories of the East European Platform, Western Sayan and Central Kazakhstan have become dry. As a result of the collision of Eastern Europe and North America, the mainland Lavrussia was formed.
Time of cataclysms
During the Middle Devonian period, the seas again began their offensive. Contributed to this activation of volcanoes. Drying began to sink again. The Ural-Tien-Shan geosyncline has become wider. Large parts of the East European and Siberian platforms were flooded, the sea was filled with some of the North American and Australian platforms. In parallel, the African and South American platforms remained dry.
The geological period of Devon ended with the Siberian Platform completely transferred to the land and formed the mainland Angarida,in Africa, the area of the sea has decreased, and South America has completely freed itself from the sea.
The Devonian period of the Paleozoic era is characterized by arid and hot climatic conditions, which contributed to the evaporation of moisture and reduce the territory of water bodies. Arid desert climate established in most of the continents. On land, deserts and semi-deserts were formed, the salt concentration in the seas increased. A climatic zonality was established, which was more pronounced than at the beginning of the era.
Chemical analysis of the remains of that period allowed us to establish an approximate temperature scale, characteristic of that time. The territory of modern Eastern Europe and the Urals was in the equatorial belt, and Transcaucasia - in the tropics.
The Devonian period in the final phase is characterized by a milder and more humid climate, weakening of volcanic processes. Established conditions have become suitable for the development of land living organisms.
Jawless and armored
Volcanic activity, the redistribution of land and sea, cosmic and atmospheric phenomena in the Devonian period led to the mass extinction of living creatures that appeared in previous geological periods. There was a revolution of species on land and at sea.But the biggest revival came in the world of fish. Scientists call this part of the Paleozoic era fish era.
Fish agna had no jaws and teeth, the front of their torso covered the skeleton, which was a huge advantage in the struggle for survival. One of the shellfish fossil fish, diniztis, had a terrible head with a stone "bag" about a meter long. Fishes lived in reservoirs, moving along the bottom with the help of sharp fins - thorns. Subsequently, armor-clad jawless fish became extinct, giving way to bone and cross-shaped congeners, but some of them have survived to this day. These are ocean lampreys and mixins. These ancient predators, of course, got rid of the heavy shell, and the rest of the structure and way of life is very similar to the ancient ancestors.
Heavy armored fish gave way to lighter moving descendants, with a flexible tail and powerful fins. They had powerful developed jaws and thin scales. The first bony fish are osteichthies and are the ancestors of most modern fish. Osteichthy lungs with bony skeletons instead of cartilaginous ones, were equipped with a new important organ - the air bubble.Ancestors of modern sharks and stingrays also appeared in the Devonian period. The fish were gradually divided into ray-finned (most modern fish) and cross-fin.
In an era when the land and water bodies were constantly replacing each other, the fin-finned fish managed to maintain enviable vitality. Their fins were reborn in the likeness of a brush, with which fish easily crawled from a dry place to another body of water. In addition, these amphibians had the ability to breathe both on land and in the water, and gained the name of the gypsy. Currently, some species of lungfish, wild-clawed amphibians are found in South America and Africa — places that are subject to frequent droughts. In the Indian Ocean, an ancient species of fish, the cross-haired Latimeria, was discovered not so long ago.
At the beginning of the Devonian, the surface of the earth was a collection of bare stony continents in the neighborhood of small swamps and seas. Gradually warm humid climate has a beneficial effect on the development of vegetation. Animals and plants began to massively conquer new space. In the shales of the Devonian system, many remains of arthropod invertebrates were found.On the first plants, primitive insects settled, miniature mites fed on green leaves with vegetable juice. For these insects and mites hunted the same miniature ancestors of spiders. Life was in full swing!
New inhabitants of the seas
Even more changes endured underwater world. In addition to multiple species of fish, in the Devonian period development affected invertebrate mollusks. Only bivalves, born in those times, counted 56 genera, except for them 24 genera of corals and 28 genera of cephalopods. Trilobites, tabulates, echinoderms and various gastropods lived at the bottom of the sea active lifestyle. Brachiopods, such as spiriferids and atripides, have reached their peak.
Ancestors of amphibians
All the prerequisites for the transition of the inhabitants of the reservoirs to the land were prepared by the Devonian period. The characteristic of new species of sea predators, as well as the active development of cross-hair double-breathing fishes, is a confirmation of this. An impressive Devonian is a scorpiona, ancestor of modern scorpions. These predators had a long body, which ended with a tail with a long thorn, limbs in the shape of an oar for swimming, and legs for raids to the shore, where they could hunt for small insects.It is believed that these creatures were worn on the backs of the shell in the form of a spiral, which served as gills for them. The end of the Devonian period is the time of the appearance of the first amphibians, which were called stegotsefaly.
Stegocephals are a kind of a collection of amphibians, reptiles, and fish. Outwardly, they resembled modern lizards or salamanders, but with hard shell. The size of the first amphibians is very diverse - from small, several centimeters to huge four-meter specimens.
The first algae, adapted to life on the banks of reservoirs, appeared in the Silurian period and continued to exist in the early Devonian. Riniophytes had no root system and deciduous shoots. Gradually, the warm and humid climate of the Devonian allowed them to be reborn into rain trees, the thicket of which grew thicker. To ensure the vital processes of the plant stretched to the sun, and became higher. To ensure high support required a dense tree trunk. Soft stems began to grow and turn into the first shrubs and trees. During the period of the late Devonian, thick and high forests rustled in the earth, reaching in some places up to 38 meters. Species of plants also became more diverse, along with moss adjacent horsetails and ferns.The Rinians lost their advantage and became extinct by the end of the period.
Animals and plants in the Devonian period successfully mastered the land, but nevertheless, their existence depended significantly on water, and active development of new territories proceeded in a small distance from the banks of water bodies. Places far from the seas remained bare and unpopulated. And only at the end of the period, seed ferns appeared, which became the progenitors of seed plants. An increasingly complex flora was born, lived and died. Many fallen leaves and wood were processed by microorganisms. With the evolution of flora and fauna, the first soil layer was formed.
The Paleozoic era - the birth of many mineral deposits, which are so important for humanity in the modern period. In the Devonian, in places with high humidity, manganese oxides and iron hydroxides were formed. The regions of Eastern Siberia turned out to be rich in these elements. The territories of modern Uruguay, Argentina, Australia, as well as some places in the northeast and southern Asia turned out to be filled with reef limestone.The Devonian period includes the oldest coal deposits of the planet, oil and gas reservoirs of the Ural region of Russia, in the oil regions of the USA, Canada, and the Middle East.
In places of high humidity, deposits of potassium salts were formed. Active volcanic processes led to the accumulation of copper pyrite ores, lead and zinc, and manganese iron. Thus, rich deposits of the Urals, the North Caucasus, Tatarstan and central Kazakhstan were formed. Outbreaks of magmatism led to the formation of kimberlite pipes with diamonds.
Devonian Period: Major Events
Summing up, we can identify the main events of the Devonian, which significantly influenced the development of the world in the future:
- The main continental land massifs are defined.
- The formation of a green cover of land.
- The evolution of plants, the emergence of new forms and species.
- Metamorphosis in the world of fish.