Jurassic period. Jurassic system (period) The historical period follows the Jurassic
Jurassic geological period, Jura, Jurassic system, middle Mesozoic period. Began 200-199 million years ago. n. and ended 144 million liters. n.
For the first time, deposits of this period were discovered and described in the Jura (mountains in Switzerland and France), hence the name of the period. The deposits of the Jurassic period are very diverse: limestones, clastic rocks, shales, igneous rocks, clays, sands, conglomerates, formed in a wide variety of conditions. The deposits of that time are quite diverse: limestones, clastic rocks, shales, igneous rocks, clays, sands, conglomerates, formed in a wide variety of conditions.
Jurassic tectonics: At the beginning of the Jurassic period, the single supercontinent Pangea began to break up into separate continental blocks. Shallow seas formed between them. Intense tectonic movements at the end of the Triassic and the beginning of the Jurassic periods contributed to the deepening of large bays, which gradually separated Africa and Australia from Gondwanaland. The gulf between Africa and America has deepened. Depressions formed in Eurasia: German, Anglo-Paris, West Siberian. The Arctic Sea flooded the northern coast of Laurasia. It was due to this that the climate of the Jurassic period became more humid. During the Jurassic period, the outlines of the continents began to form: Africa, Australia, Antarctica, North and South America. And although they are located differently than now, they were formed precisely in the Jurassic period.
Climate and vegetation of the Jurassic period
Volcanic activity at the end of the Triassic - beginning of the Jurassic period caused transgression of the sea. The continents separated and the climate in the Jurassic period became more humid than in the Triassic. In place of the deserts of the Triassic period, lush vegetation grew in the Jurassic period. Huge areas were covered with lush vegetation. Jurassic forests consisted primarily of ferns and gymnosperms.
The warm and humid climate of the Jurassic period contributed to the vigorous development of the planet's flora.
Ferns, conifers and cycads formed vast swampy forests. Araucarias, thujas, and cycads grew on the coast. Ferns and horsetails formed vast forest areas. At the beginning of the Jurassic period, about 195 million years ago. n. Throughout the northern hemisphere, the vegetation was quite monotonous. The northern plant belt was dominated by ginkgo and herbaceous ferns. During the Jurassic period, ginkgos were very widespread. Groves of ginkgo trees grew throughout the belt.
The southern plant belt was dominated by cycads and tree ferns.
Ferns from the Jurassic period survive today in some parts of the wild. Horsetails and mosses were almost no different from modern ones.
animals: Jurassic period - the dawn of the age of dinosaurs. It was the lush development of vegetation that contributed to the emergence of many species of herbivorous dinosaurs. The increase in the number of herbivorous dinosaurs gave impetus to the increase in the number of predators. Dinosaurs settled all over the land and lived in forests, lakes, and swamps. The range of differences between them is so great that family ties between them are established with great difficulty. The diversity of dinosaur species during the Jurassic period was great. They could be the size of a cat or chicken, or they could reach the size of huge whales.
The Jurassic period is the time when many famous dinosaurs lived. Of the lizards, these are Allosaurus and Diplodocus. Of the ornithischians, this is the stegosaurus.
During the Jurassic period, winged lizards - pterosaurs - reigned supreme in the air. They appeared in the Triassic, but their heyday was precisely in the Jurassic period. Pterosaurs were represented by two groups: pterodactyls and rhamphorhynchus.
During the Jurassic period, the first birds or something between birds and lizards appeared. Creatures that appeared in the Jurassic period and have the properties of lizards and modern birds are called Archeopteryx. The first birds were Archeopteryx, the size of a pigeon. Archeopteryx lived in forests. They ate mainly insects and seeds.
Bivalves displace brachiopods from shallow waters. Brachiopod shells are replaced by oysters. Bivalve mollusks fill all life niches of the seabed. Many stop collecting food from the ground and switch to pumping water using their gills. Other important events took place in the warm and shallow seas of the Jurassic period.
The Jurassic period gave rise to many species of plesiosaurs and ichthyosaurs, competing with fast-moving sharks and extremely agile bony fish. and in the depths of the sea, Leopleuradon non-stop patrolled its territory in search of food.
But one creature could rightfully be called the master of the Jurassic seas. This is a giant Liopleurodon weighing up to 25 tons. Liopleurodon was the most dangerous predator of the Jurassic seas, and perhaps in the entire history of the planet.
And Switzerland. The beginning of the Jurassic period is determined by radiometric method at 185±5 million years, the end - at 132±5 million years; the total duration of the period is about 53 million years (according to 1975 data).
The Jurassic system in its modern extent was identified in 1822 by the German scientist A. Humboldt under the name “Jurassic formation” in the Jura mountains (Switzerland), Swabian and Franconian Albs (). In the territory, Jurassic deposits were first established by the German geologist L. Buch (1840). The first scheme of their stratigraphy and division was developed by the Russian geologist K. F. Roulier (1845-49) in the Moscow region.
Divisions. All the main divisions of the Jurassic system, which were subsequently included in the general stratigraphic scale, are identified in the territory of Central Europe and Great Britain. The division of the Jurassic system into departments was proposed by L. Buch (1836). The foundations of the staged division of the Jurassic were laid by the French geologist A. d'Orbigny (1850-52). The German geologist A. Oppel was the first to produce (1856-58) a detailed (zonal) division of Jurassic deposits. See table.
Most foreign geologists classify the Callovian Stage as the middle section, citing the priority of the three-member division of the Jurassic (black, brown, white) by L. Bukh (1839). The Tithonian Stage is recognized in the sediments of the Mediterranean biogeographical province (Oppel, 1865); for the northern (boreal) province, its equivalent is the Volgian stage, first identified in the Volga region (Nikitin, 1881).
general characteristics. Jurassic deposits are widespread on all continents and are present in the periphery, parts of ocean basins, forming the base of their sedimentary layer. By the beginning of the Jurassic period, two large continental masses were separated in the structure of the earth's crust: Laurasia, which included platforms and Paleozoic folded regions of North America and Eurasia, and Gondwana, which united the platforms of the Southern Hemisphere. They were separated by the Mediterranean geosynclinal belt, which was the Tethys oceanic basin. The opposite hemisphere of the Earth was occupied by the Pacific Ocean depression, along the margins of which geosynclinal regions of the Pacific geosynclinal belt developed.
In the Tethys oceanic basin, throughout the Jurassic period, deep-sea siliceous, clayey and carbonate sediments accumulated, accompanied in places by manifestations of submarine tholeiitic-basaltic volcanism. The wide southern passive margin of Tethys was an area of accumulation of shallow-water carbonate sediments. On the northern margin, which in different places and at different times had both an active and passive character, the composition of sediments is more variegated: sandy-clayey, carbonate, in places flysch, sometimes with the manifestation of calc-alkaline volcanism. Geosynclinal areas of the Pacific belt developed in the regime of active margins. They are dominated by sandy-clayey sediments, a lot of siliceous ones, and volcanic activity was very active. The main part of Laurasia in the Early and Middle Jurassic was land. Marine transgressions from geosynclinal belts captured in the Early Jurassic only the territories of Western Europe, the northern part of Western Siberia, the eastern margin of the Siberian Platform, and in the Middle Jurassic the southern part of the East European Platform. At the beginning of the Late Jurassic, the transgression reached its maximum, spreading to the western part of the North American platform, the eastern European platform, all of Western Siberia, the Ciscaucasia and the Transcaspian region. Gondwana remained dry land throughout the Jurassic period. Marine transgressions from the southern edge of Tethys captured only the northeastern part of the African and northwestern part of the Hindustan platform. The seas within Laurasia and Gondwana were vast but shallow epicontinental basins where thin sandy-clayey sediments accumulated, and in the Late Jurassic in areas adjacent to the Tethys - carbonate and lagoonal (gypsum and salt-bearing) sediments. In the rest of the territory, Jurassic deposits are either absent or represented by continental sandy-clayey, often coal-bearing strata, filling individual depressions. The Pacific Ocean in the Jurassic was a typical oceanic basin, where thin carbonate-siliceous sediments and covers of tholeiitic basalts accumulated, preserved in the western part of the basin. At the end of the Middle - beginning of the Late Jurassic, the formation of “young” oceans began; The opening of the Central Atlantic, the Somali and North Australian basins of the Indian Ocean, and the Amerasian basin of the Arctic Ocean occurs, thereby beginning the process of dismemberment of Laurasia and Gondwana and the separation of modern continents and platforms.
The end of the Jurassic period is the time of manifestation of the Late Cimmerian phase of Mesozoic folding in geosynclinal belts. In the Mediterranean belt, folding movements manifested themselves in places at the beginning of the Bajocian, in Pre-Callovian time (Crimea, Caucasus), and at the end of the Jurassic (Alps, etc.). But they reached a particular scale in the Pacific belt: in the Cordillera of North America (Nevadian folding), and the Verkhoyansk-Chukotka region (Verkhoyansk folding), where they were accompanied by the introduction of large granitoid intrusions, and completed the geosynclinal development of the regions.
The organic world of the Earth in the Jurassic period had a typically Mesozoic appearance. Among marine invertebrates, cephalopods (ammonites, belemnites) flourish; bivalves and gastropods, six-rayed corals, and “irregular” sea urchins are widespread. Among vertebrates in the Jurassic period, reptiles (lizards) predominated sharply, reaching gigantic sizes (up to 25-30 m) and great diversity. There are known terrestrial herbivores and predatory lizards (dinosaurs), sea-swimming ones (ichthyosaurs, plesiosaurs), and flying lizards (pterosaurs). Fish are widespread in water basins; the first (toothed) birds appear in the air in the Late Jurassic. Mammals, represented by small, still primitive forms, are not very common. The land cover of the Jurassic period is characterized by the maximum development of gymnosperms (cycads, bennetites, ginkgos, conifers), as well as ferns.
And was replaced by chalk, and had a duration of about 56 million years.
Geography and climate
During the Jurassic period, the supercontinent Pangea began to split into two separate continents:
- the northern part known as Laurasia (which eventually split into North America and Eurasia, opening basins to the Atlantic Ocean and the Gulf of Mexico)
- the southern part - Gondwanaland - drifted east (and eventually divided into Antarctica, Madagascar, India and Australia, and its western part formed Africa and South America).
This process of Pangea's separation, along with warmer global temperatures, allowed reptiles such as dinosaurs to diversify and dominate the Earth for long periods of time.
Plant life
During the Mesozoic era, plants developed the ability to lead a terrestrial lifestyle and not be limited only to the oceans. By the beginning of the Jurassic, life came from bryophytes, low-growing bryophytes and liverworts, which had no vascular tissue and were limited to wet, marshy areas.
Ginkgo trees
Ferns and gingaceae, which had roots and vascular tissue for transporting water and nutrients, and reproduced by spores, were the dominant plants of the Early Jurassic. During the Jurassic period, a new way of plant reproduction appeared. Gymnosperms, such as conifers, have evolved pollen that is dispersed over long distances by the wind to pollinate female cones. This method of reproduction made it possible to significantly increase the number of gymnosperms by the end of the Jurassic period. Flowering plants did not evolve until the Cretaceous period.
Age of Dinosaurs
As depicted in the movie Jurassic Park, reptiles were the dominant animal life form during the Jurassic period. They overcame evolutionary obstacles that limited . Reptiles had strong, ossified skeletons with advanced muscular systems to support and move the body. Some of the largest animals that ever lived were the dinosaurs of the Jurassic period. Reptiles could also develop amniotic eggs that were incubated on land.
sauropods
Sauropods (lizard-footed dinosaurs) are herbivorous quadrupeds with long necks and heavy tails. Many sauropods, such as brachiosaurs, were huge. Representatives of some genera had a body length of about 25 m, and weight ranged from 50-100 tons, which makes them the largest land animals that have ever existed on Earth. Their skulls were relatively small, with nostrils raised high towards the eyes. Such small skulls meant very small brains. Despite their small brains, this group of animals flourished during the Jurassic period and had a wide geographic distribution. Sauropod fossils have been found on every continent except Antarctica. Other famous Jurassic dinosaurs include stegosaurs and flying pterosaurs.
Carnosaurs were one of the main predators of the Mesozoic era. The genus Allosaurus was one of the most widespread carnosaurs in North America. They are similar to later tyrannosaurs, although studies have shown that they have little in common. Allosaurs had strong hind limbs, heavy front legs and long jaws.
Early mammals
Adelobazilevs
Dinosaurs may have been the dominant land animals, but they were not the only fauna. Early mammals were mostly very small herbivores or insectivores, and did not compete with larger reptiles. Adelobasileus is a predatory ancestor of mammals. He had a special structure of the inner ear and jaws. This animal appeared at the end of the Triassic period.
In August 2011, scientists from China announced the discovery of Yuramaya. This tiny mid-Jurassic animal caused excitement among scientists because it was a clear ancestor of placental mammals, indicating that mammals evolved much earlier than previously thought.
Sea life
Plesiosaur
The Jurassic period was also very diverse. The largest marine predators were plesiosaurs. These carnivorous marine reptiles typically had wide bodies and long necks with four flipper-shaped limbs.
Ichthyosaur is a marine reptile that was most common in the Early Jurassic period. Because some fossils have been found with smaller individuals of their species inside their bodies, it is suggested that these animals may have been among the first to experience internal pregnancy and give birth to live young.
Cephalopods were also widespread during the Jurassic period and included the ancestors of modern squids. Among the most beautiful fossils of marine life are the spiral-shaped shells of ammonites.
For the first time, deposits of this period were found in the Jura (mountains in Switzerland and France), hence the name of the period. The Jurassic period is divided into three divisions: Leyas, Doger and Malm.
The deposits of the Jurassic period are quite diverse: limestones, clastic rocks, shales, igneous rocks, clays, sands, conglomerates, formed in a wide variety of conditions.
Sedimentary rocks containing many representatives of fauna and flora are widespread.
Intense tectonic movements at the end of the Triassic and the beginning of the Jurassic periods contributed to the deepening of large bays, which gradually separated Africa and Australia from Gondwanaland. The gulf between Africa and America has deepened. Depressions formed in Eurasia: German, Anglo-Paris, West Siberian. The Arctic Sea flooded the northern coast of Laurasia.
Intense volcanism and mountain-building processes determined the formation of the Verkhoyansk fold system. The formation of the Andes and Cordilleras continued. Warm sea currents reached Arctic latitudes. The climate became warm and humid. This is evidenced by the significant distribution of coral limestones and the remains of thermophilic fauna and flora. Very few deposits of dry climates are found: lagoonal gypsum, anhydrites, salts and red sandstones. The cold season already existed, but it was characterized only by a decrease in temperature. There was no snow or ice.
The climate of the Jurassic period depended not only on sunlight. Many volcanoes and outpourings of magma onto the bottom of the oceans heated the water and atmosphere, saturating the air with water vapor, which then rained onto the land, flowing in stormy streams into lakes and oceans. This is evidenced by numerous freshwater deposits: white sandstones alternating with dark loams.
The warm and humid climate favored the flourishing of the plant world. Ferns, cycads, and conifers formed vast swampy forests. Araucarias, thujas, and cycads grew on the coast. Ferns and horsetails formed the undergrowth. In the Lower Jurassic, throughout the northern hemisphere, vegetation was quite monotonous. But starting from the Middle Jurassic, two plant zones can be identified: the northern, in which ginkgo and herbaceous ferns predominated, and the southern with bennetites, cycads, araucarias, and tree ferns.
The characteristic ferns of the Highland period were matonia, which are still preserved in the Malayan
archipelago. Horsetails and mosses were almost no different from modern ones. The place of extinct seed ferns and cordaites is taken by cycads, which still grow in tropical forests.
Ginkgo plants were also widespread. Their leaves turned their edges towards the sun and resembled huge fans. From North America and New Zealand to Asia and Europe, dense forests of coniferous plants - araucarias and bennetites - grew. The first cypress and possibly spruce trees appear.
Representatives of the Jurassic conifers also include sequoia - the modern giant California pine. Currently, redwoods remain only on the Pacific coast of North America. Some forms have been preserved. even more ancient plants, for example glassopteris. But there are few such plants, since they were replaced by more advanced ones.
The lush vegetation of the Jurassic period contributed to the widespread distribution of reptiles. Dinosaurs have evolved significantly. Among them, lizard-hatched and ornithischian are distinguished. Lizards moved on four legs, had five toes on their feet, and ate plants. Most of them had a long neck, small head and long tail. They had two brains: one small one in the head; the second is much larger in size - at the base of the tail.
The largest of the Jurassic dinosaurs was the Brachiosaurus, reaching a length of 26 m and weighing about 50 tons. It had columnar legs, a small head, and a thick long neck. Brachiosaurs lived on the shores of Jurassic lakes and fed on aquatic vegetation. Every day, the brachiosaurus needed at least half a ton of green mass.
Diplodocus is the oldest reptile, its length was 28 m. It had a long thin neck and a long thick tail. Like a brachiosaurus, Diplodocus walked on four legs, the hind legs being longer than the front ones. Diplodocus spent most of its life in swamps and lakes, where it grazed and escaped from predators.
Brontosaurus was relatively tall, had a large hump on its back and a thick tail. Its length was 18 m. The vertebrae of the brontosaurus were hollow. Chisel-shaped small teeth were densely located on the jaws of the small head. The brontosaurus lived in swamps and on the shores of lakes.
Jurassic period (Jurassic)- middle (second) period of the Mesozoic era. Began 201.3 ± 0.2 million years ago, ended 145.0 million years ago. Thus it continued for about 56 million years. A complex of sediments (rocks) corresponding to a given age is called the Jurassic system. In different regions of the planet, these deposits differ in composition, genesis, and appearance.
For the first time, deposits of this period were described in the Jura (mountains in Switzerland and France); This is where the name of the period came from. The deposits of that time are quite diverse: limestones, clastic rocks, shales, igneous rocks, clays, sands, conglomerates, formed in a wide variety of conditions.
Flora
In the Jurassic, vast areas were covered with lush vegetation, primarily diverse forests. They mainly consisted of ferns and gymnosperms.
Cycads are a class of gymnosperms that predominated in the green cover of the Earth. Nowadays they are found in the tropics and subtropics. Dinosaurs roamed under the shade of these trees. Externally, cycads are so similar to low (up to 10-18 m) palm trees that even Carl Linnaeus placed them among palm trees in his plant system.
During the Jurassic period, groves of gingkovic trees grew throughout the then temperate zone. Ginkgos are deciduous (unusual for gymnosperms) trees with an oak-like crown and small fan-shaped leaves. Only one species has survived to this day - ginkgo biloba.
Conifers were very diverse, similar to modern pines and cypresses, which flourished at that time not only in the tropics, but had already mastered the temperate zone. The ferns gradually disappeared.
Fauna
Marine organisms
Compared to the Triassic, the population of the seabed has changed greatly. Bivalves displace brachiopods from shallow waters. Brachiopod shells are replaced by oysters. Bivalve mollusks fill all life niches of the seabed. Many stop collecting food from the ground and switch to pumping water using their gills. A new type of reef community is emerging, approximately the same as what exists now. It is based on six-rayed corals that appeared in the Triassic.
Land animals of the Jurassic period
One of the fossil creatures that combines the characteristics of birds and reptiles is Archeopteryx, or the first bird. His skeleton was first discovered in the so-called lithographic shales in Germany. The discovery was made two years after the publication of Charles Darwin's On the Origin of Species and became a strong argument in favor of the theory of evolution. Archeopteryx still flew quite poorly (gliding from tree to tree), and was approximately the size of a crow. Instead of a beak, it had a pair of toothy, albeit weak, jaws. It had free fingers on its wings (of modern birds, only hoatzin chicks have them).
During the Jurassic period, small, furry, warm-blooded animals called mammals lived on Earth. They live next to dinosaurs and are almost invisible against their background. In the Jurassic, mammals were divided into monotremes, marsupials and placentals.
Dinosaurs (English Dinosauria, from ancient Greek δεινός - terrible, terrible, dangerous and σαύρα - lizard, lizard) lived in forests, lakes, and swamps. The range of differences between them is so great that family ties between them are established with great difficulty. There were dinosaurs ranging in size from a cat to a whale. Different types of dinosaurs could walk on two or four limbs. Among them were both predators and herbivores.
Scale
Geochronological scale | |||
---|---|---|---|
Eon | Era | Period | |
F A n e R O h O th | Cenozoic | Quaternary | |
Neogene | |||
Paleogene | |||
Mesozoic | Chalk | ||
Yura | |||
Triassic | |||
Paleozoic | Permian | ||
Carbon | |||
Devonian | |||
Silur | |||
Ordovician | |||
Cambrian | |||
D O To e m b R And th | P R O T e R O h O th | Neo- Proterozoic | Ediacaran |
Cryogenium | |||
Tony | |||
Meso- Proterozoic | Stenius | ||
Ectasy | |||
Kalimium | |||
Paleo- Proterozoic | Staterius | ||
Orosirium | |||
Riasiy | |||
Siderius | |||
A R X e th | Neoarchaean | ||
Mesoarchean | |||
Paleoarchaean | |||
Eoarchaean | |||
Katarhey |
Jurassic System Division
The Jurassic system is divided into 3 divisions and 11 tiers:
system | Department | tier | Age, million years ago | |
---|---|---|---|---|
Chalk | Lower | Berriasian | less | |
Jurassic period | Upper (malm) | Titonian | 145,0-152,1 | |
Kimmeridge | 152,1-157,3 | |||
Oxford | 157,3-163,5 | |||
Average (dogger) | Callovian | 163,5-166,1 | ||
Bathian | 166,1-168,3 | |||
Bayocian | 168,3-170,3 | |||
Aalensky | 170,3-174,1 | |||
Lower (lias) | Toarsky | 174,1-182,7 | ||
Pliensbachian | 182,7-190,8 | |||
Sinemyursky | 190,8-199,3 | |||
Hettangian | 199,3-201,3 | |||
Triassic | Upper | Rhetic | more | |
Subsections are given according to IUGS as of January 2013 |
Belemnite rostra Acrofeuthis sp. Early Cretaceous, Hauterivian
Shells of the brachiopod Kabanoviella sp. Early Cretaceous, Hauterivian
Shell of the bivalve Inoceramus aucella Trautschold, Early Cretaceous, Hauterivian
Skeleton of the saltwater crocodile Stenosaurus, Steneosaurus boltensis Jaeger. Early Jurassic, Germany, Holtzmaden. Among saltwater crocodiles, the Thalattosuchus stenosaurus was the least specialized form. It did not have flippers, but ordinary five-fingered limbs, like those of land animals, although somewhat shortened. In addition, a powerful bone armor made of plates has been preserved on the back and belly.
Three of the specimens presented on the wall (the crocodile Sthenosaurus and two ichthyosaurs - Stenopterygium and Eurynosaurus) were found at one of the world's largest sites of Early Jurassic marine fauna GOLZMADEN (about 200 million years ago; Bavaria, Germany). For several centuries, slate was mined here and used as a building and decorative material.
At the same time, a huge number of remains of invertebrate fish, ichthyosaurs, plesiosaurs and crocodiles were discovered. More than 300 ichthyosaur skeletons alone have been recovered.
Small flying lizards - Sordes were numerous in the vicinity of Lake Karatau. They probably ate fish and insects. Some specimens of Sordes have preserved remains of hair, which is extremely rare in other localities.
Thecodonts- a group pre-new for other archosaurs. The first representatives (1,2) were terrestrial predators with widely spaced limbs. In the process of evolution, some thecodonts acquired a semi-vertical and vertical paw position with a four-legged mode of movement (3,5,6), others - in parallel with the development of bipedality (2,7,8). Most thecodonts were terrestrial, but some of them led an amphibiotic lifestyle (6).
Crocodiles close to thecodonts. Early crocodiles (1,2,9) were terrestrial animals, marine forms with flippers and a caudal fin also existed in the Mesozoic (10), and modern crocodiles are adapted to an amphibiotic lifestyle (11).
Dinosaurs- the central and most striking group of archosaurs. Large predatory carnosaurs (14,15) and small predatory cepurosaurs (16,17,18), as well as herbivorous ornithopods (19,20,21,22) were bipedal. Others used quadrupedal locomotion: sauropods (12,13), ceratopsians (23), stegosaurs (24) and antiposaurs (25). Sauropods and duck-billed dinosaurs (21) adopted an amphibiotic lifestyle to varying degrees. One of the most highly organized among archosaurs were flying lizards (26,27,28), which had wings with a flying membrane, hair and, possibly, a constant body temperature.
Birds- are considered direct descendants of Mesozoic archosaurs.
Small terrestrial crocodiles, grouped as Notosuchia, were widespread in Africa and South America during the Cretaceous period.
Part of the skull of a sea lizard - pliosaur. Pliosaurus cf. grandis Owen, Late Jurassic, Volga region. Pliosaurs, as well as their closest relatives, plesiosaurs, were perfectly adapted to the aquatic environment. They were distinguished by a large head, short neck and long, powerful, flipper-like limbs. Most pliosaurs had dagger-shaped teeth, and they were the most dangerous predators of the Jurassic seas. This sample, 70 cm long, is only the anterior third of the pliosaur skull, and the total length of the animal was 11-13 m. The pliosaur lived 150-147 million years ago.
Larva of the Coptoclava longipoda Ping beetle. This is one of the most dangerous predators in the lake.
Apparently, in the middle of the Cretaceous period, conditions in the lakes changed greatly and many invertebrates had to move into rivers, streams or temporary reservoirs (caddis flies, the larvae of which build tube houses from grains of sand; flies, bivalves). The bottom sediments of these reservoirs are not preserved; flowing waters erode them, destroying the remains of animals and plants. Organisms that migrate to such habitats disappear from the fossil record.
Houses made of grains of sand, which were built and carried by caddisfly larvae, are very characteristic of Early Cretaceous lakes. In later eras, such houses are found mainly in flowing waters
Larvae of the caddisfly Terrindusia (reconstruction)
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