A period not related to the Mesozoic era. Fauna and flora in the Mesozoic. The development of life in the Triassic, Jurassic and Cretaceous periods
| Parameter name | Meaning |
| Article subject: | Mesozoic era. |
| Rubric (thematic category) | Geology |
The Mesozoic era, which lasts 183 million years, is divided into three periods - Triassic, Jurassic and Cretaceous. Accordingly, it is subdivided into systems and the Mesozoic group of deposits.
The triassic system got its name in connection with the clear division of its deposits into three parts - the Lower, Middle and Upper Triassic. Accordingly, the Triassic period (35.0 million years) is divided into three sections - early, middle and late.
In the Mesozoic, the continents of the Northern and Southern Hemispheres were separated by a vast sea basin elongated in the latitudinal direction. He got the name Tethys- in honor of the ancient Greek goddess of the sea.
At the beginning of the Triassic, powerful volcanic eruptions occurred in some regions of the globe. Thus, in Eastern Siberia, outpourings of basaltic magma formed a sequence of basic rocks, which occur in the form of huge covers. Such coverings are called traps"(Swedish" trappa - stairs). It is worth saying that they are characterized by columnar separation in the form of stairs. Volcanic eruptions have also occurred in Mexico and Alaska, Spain and North Africa. In the Southern Hemisphere, Triassic volcanism has manifested itself sharply in New Caledonia, New Zealand, the Andes and other areas.
The Triassic saw one of the largest sea regressions in Earth's history. It coincided with the beginning of a new folding, which continued throughout the Mesozoic and was called "Mesozoic". The folded structures that arose at that time were called "mesozoid".
The Jura system is named after the Jura Mountains in Switzerland. In the Jurassic period, which lasted 69.0 million years, a new transgression of the sea began. But at the end of the Jurassic, in the region of the Tethys Ocean (Crimea, the Caucasus, the Himalayas, etc.), and especially noticeably in the region of the Pacific margins, mountain-building movements resumed. Οʜᴎ led to the formation of mountain structures of the outer Pacific ring: Verkhoyansk-Kolyma, Far Eastern, Andean, Cordillera. Folding was accompanied by active volcanic activity. In South Africa and South America (the Paraná river basin), large outpourings of basic lavas of a trap character occurred at the beginning of the Jurassic. The thickness of the basalt strata here reaches more than 1000 meters.
The Cretaceous system got its name due to the fact that layers of white chalk are widespread in its deposits. The Cretaceous period lasted 79.0 million years. Its beginning coincided with the most extensive sea transgression. According to one of the hypotheses, the northern supercontinent Laurasia at that time broke up into a number of separate continents: East Asian, North European, North American. Gondwana also broke up into separate continental masses: South American, African, Indian, Australian and Antarctic. In the Mesozoic, perhaps all modern oceans were formed, except, apparently, the more ancient Pacific Ocean.
In the Late Cretaceous, in the territories adjacent to the Pacific Ocean, a powerful phase of Mesozoic folding manifested itself. Less intense mountain-building movements at that time took place in a number of areas of the Mediterranean region (Eastern Alps, Carpathians, Transcaucasia). As in the Jurassic, folding was accompanied by intense magmatism.
Mesozoic rocks are "pierced" by granite intrusions introduced into them. And in the vast expanses of the Siberian, Indian, African-Arabian platforms at the end of the Mesozoic, grandiose outpourings of basalt lavas occurred, which formed trap covers (Swedish ʼʼ trapʼʼ - stairs). Now they come to the surface, for example, along the banks of the Nizhnyaya Tunguska River. Here one can observe remnants of solid basalts rising to several hundred meters, which were previously embedded in sedimentary rocks, destroyed after coming to the surface by the processes of weathering and erosion. Vertical ledges of black (dark gray), called ʼʼpillarsʼʼ, traps alternate with horizontal platforms. This is why they are loved by climbers and tourists. The thickness of such covers on the Deccan Plateau in Hindustan reaches 2000-3000 m.
O rgani ch i ch e s k i y r m e s o s o o i. At the turn of the Paleozoic and Mesozoic eras, the animal and plant world was significantly updated (Fig. 14, 15). The Triassic period is characterized by the appearance in the seas of new cephalopods (ammonites, belemnites) and lamella-gill mollusks, six-ray corals and other groups of animals. Bony fish appeared.
On land, this was the time of the dominance of reptiles. New groups of them arose - the first lizards, turtles, crocodiles, snakes. At the beginning of the Mesozoic, the first mammals appeared - small marsupials the size of a modern rat.
In the Triassic - Jura, belemnites appeared and flourished, giant herbivorous and predatory reptile dinosaurs (Greek "dinos" - terrible, "savros" - lizard). Οʜᴎ reached a length of 30 m or more and weighed up to 60 tons. Dinosaurs (Fig. 16) mastered not only land, but also the sea. Ichthyosaurs lived here (Greek "ichthys" - fish) - large predatory fish lizards, reaching a length of more than 10 m and resembling modern dolphins. At the same time, the first flying lizards appeared - pterosaurs (Greek "pteron" - wing), "savros" - lizard). These were mostly small (up to half a meter) reptiles adapted to flight.
Common representatives of pterosaurs were flying lizards - rhamphorhynchus (Greek ramphos "beak," rhinos "nose) and pterodactyls (Greek "pteron" - feather, "dactylos" - finger). Their forelimbs turned into flying organs - membranous wings The main food of rhamphorhynchus was fish and insects.The smallest pterodactyls were the size of a sparrow, the largest reached the size of a hawk.
Flying lizards were not the ancestors of birds. Οʜᴎ are a special, independent evolutionary branch of reptiles, which completely died out at the end of the Cretaceous period. Birds are descended from other reptiles.
The very first bird, apparently, is Archeopteryx (Greek "archeos" - ancient, "pteron" - wing). It was a transitional form from reptiles to birds. Archeopteryx was about the size of a crow. It had short wings, sharp predatory teeth and a long tail with fan-shaped plumage. The shape of the body, the structure of the limbs and the presence of plumage, Archeopteryx was similar to birds. But in a number of ways it was still close to reptiles.
The remains of primitive mammals have been found in the Jurassic deposits.
The Cretaceous period is the time of the greatest flowering of reptiles. Dinosaurs reached enormous sizes (up to 30 m in length); their mass exceeded 50 tons. Οʜᴎ widely populated the land and waters, reigned in the air. Flying lizards in the Cretaceous period reached gigantic proportions - with a wingspan of about 8 m.
Giant sizes were characteristic in the Mesozoic and some other groups of animals. So, in the Cretaceous seas there were mollusks - ammonites, the shells of which reached 3 m in diameter.
Of the plants on land, starting from the Triassic period, gymnosperms prevailed: conifers, gingkoves, etc.; from spores - ferns. In the Jurassic period, ground vegetation developed rapidly. At the end of the Cretaceous, angiosperms appeared; grass cover formed on land.
At the end of the Cretaceous period, the organic world again underwent drastic changes. Many invertebrates and most giant lizards died out. The reasons for their extinction have not been reliably established. According to one hypothesis, the death of dinosaurs is associated with a geological catastrophe that occurred about 65 million years ago. It is believed that then a large meteorite collided with the Earth.
In the 70s of the twentieth century. University of California geologist Walter Alvarez and
his father, physicist Luis Alvarez, discovered in the boundary Cretaceous-Paleogene deposits of the Gubbio section (Italy) an unusually high content of iridium - an element contained in large quantities in meteorites. An anomalous content of iridium was also found at the Cretaceous–Paleogene boundary in other
regions of the globe. In this regard, the father and son of Alvarez put forward a hypothesis about the collision with the Earth of a large cosmic body of an asteroid size. The consequence of the collision was the mass extinction of Mesozoic plants and animals, in particular dinosaurs. This happened about 65 million years ago at the turn of the Mesozoic and Cenozoic eras.
Hosted on ref.rf
At the moment of collision, myriads of meteorite particles and terrestrial matter rose in a giant cloud into the sky and covered the Sun for years. The earth was plunged into darkness and cold.
Numerous geochemical studies were carried out in the first half of the 1980s. Οʜᴎ have shown that the content of iridium in the boundary Cretaceous-Paleogene deposits is indeed very high - two or three orders of magnitude higher than its average content (clarke) in the earth's crust.
At the end of the Late Late Age, large groups of higher plants also disappeared.
Useful mesozoic fossils.
Mesozoic deposits contain many minerals. Deposits of ore minerals were formed as a result of the manifestation of basaltic magmatism.
The widespread Triassic weathering crust contains deposits of kaolins and bauxites (Urals, Kazakhstan). In the Jurassic and Cretaceous periods, powerful coal accumulation took place. In Russia, deposits of Mesozoic brown coal are located within the Lena, South Yakutsk, Kansko-Achinsk, Cheremkhovo, Chulym-Yenisei, Chelyabinsk basins, in the Far East and in other areas.
The famous oil and gas fields of the Middle East, Western Siberia, as well as Mangyshlak, Eastern Turkmenistan and Western Uzbekistan are confined to the Jurassic and Cretaceous deposits.
In the Jurassic, oil shale was formed (Volga region and General Syrt), sedimentary iron ores (Tula and Lipetsk regions), phosphorites (Chuvashia, Moscow region, General Syrt, Kirov region).
Phosphorite deposits are associated with Cretaceous deposits (Kursk, Bryansk, Kaluga, etc.).
Hosted on ref.rf
region) and bauxites (Hungary, Yugoslavia, Italy, France). Deposits of polymetallic ores (gold and silver, copper, lead, zinc, tin, molybdenum, tungsten, etc.) are associated with Cretaceous granite intrusions and basaltic outpourings. These are, for example, the Sadon (Northern Caucasus) deposit of polymetallic ores, tin ores of Bolivia, etc. Two of the richest Mesozoic ore belts stretch along the shores of the Pacific Ocean: from Chukotka to Indochina and from Alaska to Central America. In South Africa and Eastern Siberia, diamond deposits are associated with Cretaceous deposits.
Cenozoic era. The Cenozoic era lasts 65 million years. In the international scale of geological time, it is divided into "Tertiary" and "Quaternary" periods. In Russia and other states of the former Soviet Union, the Cenozoic is divided into three periods: Paleogene, Neogene, and Anthropogenic (Quaternary).
The Paleogene period (40.4 million years) is divided into early - Paleocene (10.1 million years), middle - Eocene (16.9 million years) and late - Oligocene (13.4 million years) era. In the Northern Hemisphere in the Paleogene, the North American and Eurasian continents existed. They were separated by the depression of the Atlantic Ocean. In the Southern Hemisphere, the continents continued to develop independently, breaking away from Gondwana and separated by depressions of the Atlantic and Indian oceans.
In the Eocene epoch, the first phase of powerful Alpine folding appeared in the Mediterranean region. It caused the uplift of some of the central sections of this area. By the end of the Paleogene, the sea completely left the territory of the Himalayan-Indostan part of the Tethys.
The formation of numerous deep faults in the North Strait and adjacent areas of Ireland, Scotland, Northern England and the Hebrides; the region of Southern Sweden and the Skagerrak, as well as in the entire region of the North Atlantic (Svalbard, Iceland, West Greenland) contributed to basaltic outpourings.
At the end of the Paleogene period, discontinuous and block movements of the earth's crust were widely manifested in many parts of the globe. In a number of regions of the Western European Hercynides, a system of grabens arose (Upper Rhine, Lower Rhine). The system of narrow meridionally elongated grabens (Dead and Red Seas, Lake Alberta, Nyasa, Tanganyika) arose in the eastern part of the African Platform). It stretched from the northern edge of the platform almost to the extreme south at a distance of over 5000 km. Faulty dislocations here were accompanied by grandiose outpourings of basalt magmas.
The Neogene period includes two epochs: early - Miocene (19.5 million years) and late - Pliocene (3.5 million years). It is worth saying that the Neogene was characterized by active mountain building. By the end of the Neogene, alpine folding turned most of the Tethys region into the youngest alpine folded area in the structure of the earth's crust. At this time, many mountain structures acquired their modern look. There were chains of the Sunda, Moluccas, New Guinea, New Zealand, Philippine, Ryukkyu, Japanese, Kuril, Aleutian Islands, etc.
Hosted on ref.rf
Coast ranges have risen in a narrow band within the Eastern Pacific coastal margins. Mountain building also took place in the region of the Central Asian mountain belt.
In the Neogene, powerful block movements caused the subsidence of large sections of the earth's crust - the areas of the Mediterranean, Adriatic, Black, East China, South China, Japan, Okhotsk and other marginal seas, as well as the Caspian Sea.
Uplifts and subsidence of crustal blocks in the Neogene were accompanied by
initiation of deep faults. Lava flowed through them. For example,
in the Central Plateau of France. In the zone of these faults, volcanoes Vesuvius, Etna, as well as Kamchatka, Kuril, Japanese and Javanese volcanoes arose in the Neogene.
In the history of the Earth, there were frequent periods of cooling, alternating with warming. About 25 million years ago, from the end of the Paleogene, there was a cooling. One of the warmings took place at the beginning of the late Neogene (Pliocene epoch). The next cold snap formed mountain-valley and sheet glaciers in the northern hemisphere and a thick ice sheet in the Arctic. Perennial freezing of rocks in the north of Russia continues to the present.
The anthropogenic period got its name because at the beginning of this period a man appeared (Greek . "anthropos" - a person). Its former name is quaternary system. The question of the duration of the Anthropogenic period has not yet been finally resolved. Some geologists determine the duration of the Anthropogen at least 2 million years. The anthropogen is subdivided into eopleistocene(gr. "eos" - dawn, "pleistos" - the largest, "kainos" - new), Pleistocene and Holocene(gr. "voice" - all, "kainos" - new). The duration of the Holocene does not exceed 10 thousand years. But some scientists attribute the Eopleistocene to the Neogene and draw the lower boundary of the Anthropogen at the level of 750 thousand years ago.
At this time, the uplift of the Central Asian mountain-fold belt continued more actively. According to some scientists, the Tien Shan and Altai mountains have risen several kilometers during the Anthropogenic period. And the basin of Lake Baikal plunged to 1600 m.
In the Anthropogen, intense volcanic activity is manifested. The most powerful basalt eruptions in the modern era are observed in the mid-ocean ridges and other vast expanses of the ocean floor.
"Great" glaciations took place in the vast expanses of the northern continents and in the Anthropogenic period. Οʜᴎ also formed the ice sheet of Antarctica. The Eopleistocene and Pleistocene are characterized by a general cooling of the Earth's climate and the periodic occurrence of continental glaciations in the middle latitudes. In the middle Pleistocene, powerful glacial tongues descended to almost 50 ° N. latitude. in Europe and up to 40°N. in the USA. Here, the thickness of moraine deposits is a few tens of meters. Interglacial epochs were characterized by a relatively mild climate. Average temperatures increased by 6 - 12 ° C (N.V. Koronovsky, A.F. Yakushova, 1991). .
Formed by the waters of the seas and oceans, huge masses of ice in the form of glaciers moved towards the land. Frozen rocks spread over vast areas. Holocene - postglacial epoch. Its beginning coincides with the end of the last continental glaciation in Northern Europe.
O rgani ch i ch e s k i y r k a i n o o s o i. By the beginning of the Cenozoic era, belemnites, ammonites, giant reptiles, etc., are dying out.
Hosted on ref.rf
In the Cenozoic, protozoa (foraminifera), mammals, and bony fish began to actively develop. Οʜᴎ took a dominant position among other representatives of the animal world. In the Paleogene, oviparous and marsupials predominated among them (a similarity of this type of fauna was partially preserved in Australia). In the Neogene, these groups of animals recede into the background, and ungulates, proboscis, predators, rodents, and other now known classes of higher mammals begin to play the main role.
The organic world of the anthropogen is similar to the modern one. In the Anthropogenic period, humans evolved from primates that existed in the Neogene 20 million years ago.
The Cenozoic era is characterized by a wide distribution of terrestrial vegetation: angiosperms, grasses, close to modern ones.
Useful fossils of the Cainozoic. In the Paleogene period, powerful coal formation took place. Brown coal deposits are known in the Paleogene of the Caucasus, Kamchatka, Sakhalin, the USA, South America, Africa, India, Indochina, and Sumatra. Paleogenic manganese ores have been discovered in Ukraine (Nikopol), in Georgia (Chiatura), in the North Caucasus, Mangyshlak. Paleogene deposits of bauxites (Chulym-Yenisei, Akmola), oil and gas are known.
Oil and gas deposits are confined to the Neogene deposits (Baku, Maikop, Grozny, Southwestern Turkmenistan, Western Ukraine, Sakhalin). In the Black Sea basin, on the territory of the Kerch and Taman Peninsulas, during the Neogene period, iron ores were deposited in various areas.
In the Anthropogenic period, deposits of salts, building materials (crushed stone, gravel, sand, clay, loam), lake-marsh iron ores were formed; as well as placer deposits of gold, platinum, diamonds, tin, tungsten ores, precious stones, etc.
Table 5
Mesozoic era. - concept and types. Classification and features of the category "Mesozoic era." 2017, 2018.
Lesson topic:"The Development of Life in the Mesozoic Era"
The duration of the Mesozoic era is approximately 160 million years. The Mesozoic era includes the Triassic (235-185 million years ago), Jurassic (185-135 million years) and Cretaceous (135-65 million years ago) periods. The development of organic life on Earth and the evolution of the biosphere continued against the background of paleogeographical changes characteristic of this stage.
The Triassic is characterized by a general uplift of platforms and an increase in land area.
By the end of the Triassic, the destruction of most of the mountain systems that arose in the Paleozoic ended. The continents turned into huge plains, which in the next, Jurassic, period, the ocean began to advance. The climate became milder and warmer, capturing not only the tropical and subtropical zones, but also modern temperate latitudes. During the Jurassic, the climate is warm and humid. The increased rainfall caused the formation of seas, huge lakes and large rivers. The change in physical and geographical conditions affected the development of the organic world. The extinction of representatives of the marine and terrestrial biota continued, which began in the arid Permian, which was called the Permian-Triassic crisis. After this crisis, and as a result of it, the flora and fauna of the land evolved.
In biological terms, the Mesozoic was a time of transition from old, primitive to new, progressive forms. The Mesozoic world was much more diverse than the Paleozoic, fauna and flora appeared in it in a significantly updated composition.
Flora
The vegetation cover of the land at the beginning of the Triassic period was dominated by ancient coniferous and seed ferns (pteridosperms). in arid climates, these gymnosperms gravitated to moist places. On the coasts of drying reservoirs and in disappearing swamps, the last representatives of ancient club mosses, some groups of ferns, perished. By the end of the Triassic, a flora was formed in which ferns, cycads, and ginkgoes dominated. Gymnosperms flourished during this period.
In the Cretaceous, flowering plants appeared and conquered the land.
The supposed ancestor of flowering plants, according to most scientists, was closely related to seed ferns and represented one of the branches of this group of plants. Paleontological remains of primary flowering plants and a group of plants intermediate between them and gymnosperm ancestors, unfortunately, are still unknown to science.
The primary type of flowering plant was, according to most botanists, an evergreen tree or low shrub. The herbaceous type of flowering plant appeared later under the influence of limiting environmental factors. The idea of the secondary nature of the herbaceous type of angiosperms was first expressed in 1899 by the Russian botanical geographer A.N. Krasnov and the American anatomist C. Jeffrey.
The evolutionary transformation of woody forms into herbaceous ones occurred as a result of a weakening, and then a complete or almost complete decrease in the activity of the cambium. Such a transformation probably began at the dawn of the development of flowering plants. With the passage of time, it proceeded more rapidly in the most distant groups of flowering plants and eventually acquired such a wide scale that it covered all the main lines of their development.
Of great importance in the evolution of flowering plants was neoteny - the ability to reproduce at an early stage of ontogenesis. It is usually associated with limiting environmental factors - low temperature, lack of moisture and a short growing season.
Of the huge variety of woody and herbaceous forms, flowering plants turned out to be the only group of plants capable of forming complex multi-tiered communities. The emergence of these communities led to a more complete and intensive use of the natural environment, the successful conquest of new territories, especially unsuitable for gymnosperms.
In the evolution and mass dispersal of flowering plants, the role of pollinating animals is also great, especially insects. Feeding on pollen, insects carried it from one strobilus of the original angiosperm ancestors to another and, thus, were the first agents of cross-pollination. Over time, insects adapted to eat the ovules, already causing significant damage to plant reproduction. The reaction to such a negative influence of insects was the selection of adaptive forms with closed ovules.
The conquest of land by flowering plants marks one of the decisive, turning points in the evolution of animals. This parallelism between the suddenness and rapidity of the spread of angiosperms and mammals is explained by interdependent processes. The conditions associated with the flowering of angiosperms were also favorable for mammals.
Fauna
Fauna of the seas and oceans: Mesozoic invertebrates were already approaching modern ones in character. A prominent place among them was occupied by cephalopods, to which modern squids and octopuses belong. The Mesozoic representatives of this group included ammonites with a shell twisted into a "ram's horn", and belemnites, the inner shell of which was cigar-shaped and overgrown with the flesh of the body - the mantle. Ammonites were found in the Mesozoic in such quantities that their shells are found in almost all marine sediments of this time.
By the end of the Triassic, most of the ancient groups of ammonites die out, but in the Cretaceous period they are still numerous., but during the Late Cretaceous, the number of species in both groups begins to decline. The diameter of the shells of some ammonites reaches 2.5 m.
At the end of the Mesozoic, all ammonites became extinct. Of the cephalopods with an outer shell, only the genus Nautilus has survived to this day. Forms with an internal shell are more widely distributed in modern seas - octopuses, cuttlefish and squids, remotely related to belemnites.
Six-pointed corals began to actively develop(Hexacoralla), whose colonies were active reef-formers. Mesozoic echinoderms were represented by various types of crinoids, or crinoids (Crinoidea), which flourished in the shallow waters of the Jurassic and partly Cretaceous seas. However sea urchins have made the most progress. Starfish were plentiful.
Bivalve molluscs also spread strongly.
During the Jurassic, the foraminifera flourished again that survived the Cretaceous period and reached modern times. In general, unicellular protozoa were an important component in the formation of Mesozoic sedimentary rocks. The Cretaceous period was also a time of rapid development of new types of sponges and some arthropods, in particular insects and decapods.
The Mesozoic era was a time of unstoppable expansion of vertebrates. Of the Paleozoic fish, only a few moved into the Mesozoic.. Among them were freshwater sharks, marine sharks continued to evolve throughout the Mesozoic; most modern genera were already represented in the seas of the Cretaceous, in particular.
Almost all the lobe-finned fish from which the first terrestrial vertebrates developed died out in the Mesozoic. Paleontologists believed that the crossopterans became extinct by the end of the Cretaceous. But in 1938 an event occurred that attracted the attention of all paleontologists. An individual of a fish species unknown to science was caught off the South African coast. Scientists who studied this unique fish came to the conclusion that it belongs to the "extinct" group of crossopterans ( Coelacanthida). Until now this view remains the only modern representative of the ancient lobe-finned fish. He got the name Latimeria chalumnae. Such biological phenomena are referred to as "living fossils".
Sushi fauna: New groups of insects appeared on land, the first dinosaurs and primitive mammals. The most widespread in the Mesozoic were reptiles, which became truly the dominant class of this era.
With the advent of dinosaurs early reptiles became completely extinct in the middle of the Triassic cotylosaurs and mammals, as well as the last large amphibian stegocephals. Dinosaurs, which were the most numerous and diverse superorder of reptiles, have become the leading Mesozoic group of terrestrial vertebrates since the end of the Triassic. For this reason, the Mesozoic is called the era of the dinosaurs. In the Jurassic, among the dinosaurs, real monsters could be found, up to 25-30 m long (with a tail) and weighing up to 50 tons. Of these giants, such forms as the brontosaurus (Brontosaurus), diplodocus (Diplodocus) and brachiosaurus (Brachiosaurus) are best known.
The original ancestors of the dinosaurs may have been the Upper Permian eosuchia, a primitive detachment of small reptiles with a physique resembling a lizard. From them, in all likelihood, a large branch of reptiles arose - archosaurs, which then broke up into three main branches - dinosaurs, crocodiles and winged pangolins. The archosaurs were thecodonts. Some of them lived in the water and outwardly resembled crocodiles. Others, like large lizards, lived in open areas of land. These terrestrial thecodonts adapted to bipedal walking, which provided them with the ability to observe in search of prey. It was from such thecodonts, which became extinct at the end of the Triassic, that dinosaurs originated, inheriting a bipedal mode of movement, although some of them switched to a quadrupedal mode of movement. Representatives of the climbing forms of these animals, which eventually switched from jumping to gliding flights, gave rise to pterosaurs (pterodactyls) and birds. Dinosaurs included both herbivores and carnivores.
By the end of the Cretaceous, the mass extinction of characteristic Mesozoic groups of reptiles, including dinosaurs, ichthyosaurs, plesiosaurs, pterosaurs and mosasaurs, occurs.
Members of the bird class (Aves) first appear in Jurassic deposits. The only known first bird was Archeopteryx. The remains of this first bird were found near the Bavarian city of Solnhofen (Germany). During the Cretaceous, bird evolution proceeded at a rapid pace; characteristic of this time, still possessing serrated jaws. The emergence of birds was accompanied by a number of aromorphoses: they acquired a hollow septum between the right and left ventricles of the heart, lost one of the aortic arches. The complete separation of arterial and venous blood flows determines the warm-bloodedness of birds. Everything else, namely, feather cover, wings, horny beak, air sacs and double breathing, as well as shortening of the hindgut, are idioadaptations.
First mammals (Mammalia), modest animals, not exceeding the size of a mouse, descended from animal-like reptiles in the late Triassic. Throughout the Mesozoic, they remained few in number, and by the end of the era, the original genera had largely died out. Their occurrence is associated with a number of major aromorphoses, developed in representatives of one of the subclasses of reptiles. These aromorphoses include: the formation of hair and a 4-chambered heart, complete separation of arterial and venous blood flow, intrauterine development of offspring and feeding the baby with milk. Aromorphoses include development of the cerebral cortex, causing the predominance of conditioned reflexes over unconditioned ones and the possibility of adapting to changing environmental conditions by changing behavior.
Almost all Mesozoic groups of the animal and plant kingdoms retreat, die out, disappear; on the ruins of the old, a new world arises, the world of the Cenozoic era, in which life receives a new impetus to development and, in the end, the living species of organisms are formed.
Era. Continued for 56 million years. It began 201 million years ago and ended 145 million years ago. The geochronological scale of the history of the Earth of all eons, eras and periods is located.
The name "Jura" was named after the mountain range of the same name in Switzerland and France, where deposits of this period were first discovered. Later, geological formations of the Jurassic period were discovered in many other places on the planet.
In the Jurassic period, the Earth almost completely recovered from the largest in history. Various forms of life - marine organisms, land plants, insects and many animal species - begin to flourish and increase their species diversity. Dinosaurs reign in the Jurassic period - large, and sometimes just giant lizards. Dinosaurs existed almost everywhere and everywhere - in the seas, rivers and lakes, in swamps, forests, in open spaces. Dinosaurs received such a wide variety and distribution that over millions of years of evolution, some of them began to differ radically from each other. Dinosaurs included both herbivores and carnivores. Some of them were the size of a dog, while others reached a height of more than ten meters.
One of the species of lizards in the Jurassic period became the ancestor of birds. Archeopteryx, which existed just at this time, is considered an intermediate link between reptiles and birds. In addition to lizards and giant dinosaurs, warm-blooded mammals already lived on earth at that time. Mammals of the Jurassic period were mostly small in size and occupied rather insignificant niches in the living space of the earth of those times. Against the background of the prevailing number and diversity of dinosaurs, they were almost invisible. This will continue throughout the Jurassic and all subsequent periods. Mammals will become full owners of the Earth only after the Cretaceous-Paleogene extinction, when all dinosaurs disappear from the face of the planet, opening the way for warm-blooded animals.
Jurassic period animals
Allosaurus
Apatosaurus
Archeopteryx
Barosaurus
Brachiosaurus
Diplodocus
Dryosaurs
Giraffatitan
Camarasaurus
Camptosaurus
Kentrosaurus
Liopleurodon
Megalosaurus
Pterodactyls
ramphorhynchus
Stegosaurus
Scelidosaurus
Ceratosaurus
To protect your home or property, you need to use the best security systems. Alarm systems can be found at http://www.forter.com.ua/ohoronni-systemy-sygnalizatsii/. In addition, here you can buy intercoms, video cameras, metal detectors and much more.
Which he followed. The Mesozoic era is sometimes referred to as the "era of the dinosaurs" because these animals were the dominant representatives for much of the Mesozoic.
After the Permian mass extinction wiped out more than 95% of ocean life and 70% of land species, a new Mesozoic era began about 250 million years ago. It consisted of the following three periods:
Triassic period, or Triassic (252-201 million years ago)
The first big changes were seen in the type that dominated the Earth. Most of the flora that survived the Permian extinction became plants containing seeds, such as gymnosperms.
Cretaceous period, or Cretaceous (145-66 million years ago)
The last period of the Mesozoic was called the Cretaceous. In the growth of flowering terrestrial plants. They were helped by newly appeared bees and warm climatic conditions. Conifers were still plentiful during the Cretaceous.
As for the marine animals of the Cretaceous period, sharks and rays became commonplace. survivors of the Permian extinction, such as starfish, were also abundant during the Cretaceous.
On land, the first small mammals began to evolve during the Cretaceous period. First, marsupials appeared, and then other mammals. There were more birds and more reptiles. The dominance of dinosaurs continued, and the number of carnivorous species increased.
At the end of the Cretaceous and Mesozoic, another thing happened. This extinction is commonly referred to as the K-T extinction (Cretaceous-Paleogene extinction). It wiped out all dinosaurs except birds and many other life forms on Earth.
There are different versions as to why the mass disappearance occurred. Most scientists agree that it was some kind of catastrophic event that caused this extinction. Various hypotheses include massive volcanic eruptions that sent massive amounts of dust into the atmosphere, reducing the amount of sunlight reaching the Earth's surface and thereby causing the death of photosynthetic organisms such as plants and those who depended on them. Others believe that a meteorite fell to Earth, and the dust blocked the sunlight. As the plants and animals that fed on them died out, this led to predators such as carnivorous dinosaurs also dying for lack of food.
The Mesozoic era is divided into three periods: Triassic, Jurassic and Cretaceous.
Mesozoic - an era of tectonic, climatic and evolutionary activity. There is a formation of the main contours of modern continents and mountain building on the periphery of the Pacific, Atlantic and Indian oceans; the division of the landmass contributed to speciation and other important evolutionary events. The climate was warm throughout the entire time period, which also played an important role in the evolution and formation of new animal species. By the end of the era, the main part of the species diversity of life approached its modern state.
Encyclopedic YouTube
1 / 3
✪ The history of the development of life in the Mesozoic era. Part 1. Video lesson in biology Grade 11
✪ Dinosaurs (says paleontologist Vladimir Alifanov)
✪ Dinosaurs and other ancient animals (a selection of esters)
Subtitles
Geological periods
- Triassic period (251.902 ± 0.024 - 201.3 ± 0.2)
- Jurassic period (201.3 ± 0.2 - 145.0)
- Cretaceous period (145.0 - 66.0).
Tectonics and paleogeography
Compared to the vigorous mountain building of the Late Paleozoic, Mesozoic tectonic deformations can be considered relatively mild. The main tectonic event was the breakup of the Pangea supercontinent into a northern part (Laurasia) and a southern part (Gondwana). Later, they also broke up. At the same time, the Atlantic Ocean was formed, surrounded mainly by passive continental margins (for example, the east coast of North America). The extensive transgressions that prevailed in the Mesozoic led to the emergence of numerous inland seas.
By the end of the Mesozoic, the continents practically took on their modern shape. Laurasia divided into Eurasia and North America, Gondwana - into South America, Africa, Australia, Antarctica and the Indian subcontinent, the collision of which with the Asian continental plate caused intense orogeny with the rise of the Himalayan mountains.
Africa
At the beginning of the Mesozoic era, Africa was still part of the Pangea supercontinent and had a relatively common fauna with it, dominated by theropods, prosauropods and primitive ornithischian dinosaurs (by the end of the Triassic).
Late Triassic fossils are found everywhere in Africa, but are more common in the south than in the north of the continent. As is known, the time line separating the Triassic from the Jurassic period was drawn according to the global catastrophe with the mass extinction of species (Triassic-Jurassic extinction), but the African layers of this time remain poorly understood today.
Early Jurassic fossil deposits are distributed similarly to those of the Late Triassic, with more frequent outcrops in the south of the continent and fewer deposits towards the north. During the Jurassic period, such iconic groups of dinosaurs as sauropods and ornithopods increasingly spread across Africa. Paleontological layers of the middle Jurassic in Africa are poorly represented and also poorly studied.
The Late Jurassic is also poorly represented here, with the exception of the impressive collection of Jurassic Tendeguru fauna in Tanzania, whose fossils are very similar to those found in the paleobiotic Morrison Formation in western North America and date from the same period.
In the middle of the Mesozoic, about 150-160 million years ago, Madagascar separated from Africa, while remaining connected to India and the rest of Gondwana. Fossils from Madagascar have included abelisaurs and titanosaurs.
In the early Cretaceous, a part of the land that made up India and Madagascar separated from Gondwana. In the Late Cretaceous, the divergence of India and Madagascar began, which continued until the modern outlines were reached.
Unlike Madagascar, the African mainland was tectonically relatively stable throughout the Mesozoic. And yet, despite the stability, significant changes occurred in its position relative to other continents as Pangea continued to fall apart. By the beginning of the Late Cretaceous, South America separated from Africa, thus completing the formation of the Atlantic Ocean in its southern part. This event had a huge impact on the global climate by changing ocean currents.
During the Cretaceous, Africa was inhabited by allosauroids and spinosaurids. The African theropod Spinosaurus turned out to be one of the largest carnivores that lived on Earth. Among the herbivores in the ancient ecosystems of those times, titanosaurs occupied an important place.
Fossil deposits from the Cretaceous are more common than those from the Jurassic, but often cannot be radiometrically dated, making their exact age difficult to determine. Paleontologist Louis Jacobs, who has spent considerable time fieldwork in Malawi, argues that African fossil deposits "need more careful excavation" and are bound to prove "fertile ... for scientific discoveries."
Climate
During the last 1.1 billion years in the history of the Earth, there have been three successive ice age-warm cycles, called the Wilson cycles. Longer warm periods were characterized by a uniform climate, a greater diversity of flora and fauna, and a predominance of carbonate sediments and evaporites. Cold periods with glaciations at the poles were accompanied by a decrease in biodiversity, terrigenous and glacial sediments. The reason for the cyclicity is considered to be the periodic process of connecting the continents into a single continent (Pangaea) and its subsequent disintegration.
The Mesozoic era is the warmest period in the Phanerozoic history of the Earth. It almost completely coincided with the period of global warming, which began in the Triassic period and ended already in the Cenozoic era with the Little Ice Age, which continues to this day. For 180 million years, even in the polar regions there was no stable ice cover. The climate was mostly warm and even, without significant temperature gradients, although there was climatic zoning in the northern hemisphere. A large amount of greenhouse gases in the atmosphere contributed to the even distribution of heat. The equatorial regions were characterized by a tropical climate (the Tethys-Pantalassa region) with an average annual temperature of 25-30°C. Up to 45-50°N the subtropical region (Peritethys) extended, then the moderately warm boreal belt lay further, and the polar regions were characterized by a moderately cool climate.
The Mesozoic had a warm climate, mostly dry in the first half of the era and humid in the second. Slight cooling in the late Jurassic and the first half of the Cretaceous, a strong warming in the middle of the Cretaceous (the so-called Cretaceous temperature maximum), at about the same time the equatorial climatic zone appears.
Flora and fauna
Giant ferns, tree horsetails, and club mosses are dying out. In the Triassic, gymnosperms, especially conifers, flourish. In the Jurassic, seed ferns die out and the first angiosperms appear (then represented only by tree forms), which gradually spread to all continents. This is due to a number of advantages - angiosperms have a highly developed conducting system, which ensures the reliability of cross-pollination, the embryo is supplied with food reserves (due to double fertilization, a triploid endosperm develops) and is protected by shells, etc.
In the animal kingdom, insects and reptiles flourish. Reptiles occupy a dominant position and are represented by a large number of forms. In the Jurassic period, flying lizards appear and conquer the air. In the Cretaceous period, the specialization of reptiles continues, they reach enormous sizes. Some of the dinosaurs weighed up to 50 tons.
The parallel evolution of flowering plants and pollinating insects begins. At the end of the Cretaceous, cooling sets in, and the area of near-water vegetation is reduced. Herbivores are dying out, followed by carnivorous dinosaurs. Large reptiles are preserved only in the tropical zone (crocodiles). Due to the extinction of many reptiles, a rapid adaptive radiation of birds and mammals begins, occupying the vacated ecological niches. In the seas, many forms of invertebrates and sea lizards are dying out.
Birds, according to most paleontologists, evolved from one of the groups of dinosaurs. The complete separation of arterial and venous blood flow determined their warm-bloodedness. They spread widely over land and gave rise to many forms, including flightless giants.
The emergence of mammals is associated with a number of large aromorphoses that arose in one of the subclasses of reptiles. Aromorphoses: a highly developed nervous system, especially the cerebral cortex, which provided adaptation to the conditions of existence by changing behavior, moving limbs from the sides under the body, the emergence of organs that ensure the development of the embryo in the mother's body and subsequent feeding with milk, the appearance of a coat, complete separation of circulatory circles, the emergence of alveolar lungs, which increased the intensity of gas exchange and, as a result, the overall level of metabolism.
Mammals appeared in the Triassic, but could not compete with dinosaurs and for 100 million years occupied a subordinate position in the ecological systems of that time.