What happened after the Jurassic period? Jurassic system (period). Minerals of the Jurassic period
160 million years ago, the rich plant world provided food for the giant sauropods that had emerged by this time, and also provided shelter for a huge number of small mammals and dinosaurs. At this time, conifers, ferns, horsetails, tree ferns and cycads were widespread.
A distinctive feature of the Jurassic period was the appearance and flourishing of giant lizard-hipped herbivorous dinosaurs, sauropods, the largest land animals that ever existed. Despite their size, these dinosaurs were quite numerous.Their fossilized remains are found on all continents (except Antarctica) in rocks from the Early Jurassic to the Late Cretaceous, although they were most common in the second half of the Jurassic. At the same time, sauropods reach their most large sizes. They survived until the Late Cretaceous, when the huge hadrosaurs ("duck-billed dinosaurs") began to dominate the terrestrial herbivores.
Externally, all sauropods looked similar to each other: with an extremely long neck, an even longer tail, a massive but relatively short body, four column-like legs and a relatively small head. U various types Only the position of the body and the proportions of individual parts could change. For example, such sauropods of the Late Jurassic period as brachiosaurs (Brachiosaurus - “shouldered lizard”) were higher in the shoulder girdle than in the pelvic girdle, while contemporary diplodocus (Diplodocus - “double appendage”) were significantly lower, and at the same time their hips rose above their shoulders. Some sauropod species, such as Camarasaurus ("chamber lizard"), had a relatively short neck, only slightly longer than the body, while others, such as diplodocus, had a neck more than twice as long as the body.
Teeth and diet
The external similarity of sauropods masks the unexpectedly wide diversity in the structure of their teeth and, consequently, in their feeding methods.
The Diplodocus skull helped paleontologists understand the feeding method of this dinosaur. The abrasion of the teeth indicates that he plucked leaves either from below or from above him.
Many books on dinosaurs used to mention the "small, thin teeth" of sauropods, but it is now known that the teeth of some of them, such as Camarasaurs, were massive and strong enough to grind even very hard plant food, while the long and thin ones Diplodocus's pencil-shaped teeth do appear unable to withstand the significant stress of chewing hard plants.
diplodocus (Diplodocus). Its long neck allowed it to “comb” food from the highest coniferous plants. It is believed that Diplodocus lived in small herds and ate tree shoots.
In a study of diplodocus teeth carried out in recent years in England, unusual wear on their lateral surfaces was discovered. This pattern of tooth wear provided the key to understanding how these huge animals could feed. The side surface of the teeth could only wear down if something moved between them. Apparently, Diplodocus used its teeth to tear apart tufts of leaves and shoots, acting as a comb, while its lower jaw could move slightly back and forth. Most likely, when the animal stripped the plants it grabbed below by moving its head up and back, the lower jaw was displaced back (the upper teeth were located in front of the lower ones), and when it pulled on the branches located above tall trees down and back, then pushed lower jaw forward (the lower teeth were in front of the upper teeth).
Brachiosaurus probably used its shorter, slightly pointed teeth to pluck only high-lying leaves and shoots, as its body's vertical orientation dictated longer front legs, made it difficult to feed on plants growing low above the soil.
Narrow specialization
Camarasaurus, somewhat smaller in size than the giants mentioned above, had a relatively short and thicker neck and most likely fed on leaves located at an intermediate height between the feeding levels of brachiosaurs and diplodocus. It had a tall, rounded and more massive skull compared to other sauropods, as well as a more massive and stronger lower jaw, indicating a better ability to grind hard plant food.Details described above anatomical structure sauropods show that within the same ecological system (in the forests that covered most of the land at that time), sauropods ate a variety of plant foods, obtaining them differently at different levels. This division by feeding strategy and type of food, which can be seen in herbivore communities today, is called “tropical partitioning.”
Brachiosaurus reached more than 25 m in length and 13 m in height. Their fossilized remains and fossilized eggs are found in East Africa and North America. They probably lived in herds like modern elephants.
The main difference between today's herbivore ecosystems and those of the Late Jurassic, which were dominated by sauropods, concerns only the mass and height of the animals. None of the modern herbivores, including elephants and giraffes, reach a height comparable to that of most large sauropods, and no modern land animal requires such enormous amounts of food as these giants.
The other end of the scale
Some sauropods that lived in the Jurassic period reached fantastic sizes, for example, the brachiosaurus-like Supersaurus, whose remains were found in the USA (Colorado), probably weighed about 130 tons, that is, it was many times larger than a large male African elephant. But these supergiants shared land with tiny creatures hiding underground that did not belong to dinosaurs or even reptiles. The Jurassic period was a time of existence of numerous ancient mammals. These small, furred, viviparous, milk-feeding warm-blooded animals were called multitubercular because of the unusual structure of their molars: numerous cylindrical “tubercles” fused together to form uneven surfaces, perfectly adapted to grinding plant food.Polytubercles were the largest and most diverse group of mammals of the Jurassic and Cretaceous periods. They are the only omnivorous mammals Mesozoic era(the rest were specialized insectivores or carnivores). They are known from Late Jurassic deposits, but recent finds show that they are close to a little-known group of extremely ancient mammals of the Late Triassic, the so-called. Haramides.
The structure of the skull and teeth was very similar to today's rodents; they had two pairs of protruding incisors, giving them the appearance of a typical rodent. Behind the incisors there was a gap that did not contain teeth, followed by molars to the very end of the small jaws. However, the multitubercular teeth closest to the incisors had an unusual structure. In fact, these were the first false-rooted (premolar) teeth with curved sawtooth edges.
This unusual dental structure has reappeared in the process of evolution in some of the modern marsupials, for example, in the rat kangaroos of Australia, whose teeth are of the same shape and located in the same place in the jaw as the false-rooted teeth of polytubercles. When chewing food at the moment of closing the jaws, multituberculates could move the lower jaw back, moving these sharp saw-toothed teeth across the food fibers, and the long incisors could be used to pierce dense plants or the hard exoskeletons of insects.
A saurian megalosaurus (Megalosaurus) and its young that overtook an ornithischian scelidosaurus (Scelidosaurus). Scelidosaurus is an ancient species of dinosaur of the Jurassic period with unevenly developed limbs, reaching 4 m in length. Its dorsal shell helped protect itself from predators.
The combination of sharp front incisors, serrated blades and chewing teeth means that the feeding apparatus of multitubercles was quite versatile. Today's rodents are also a very successful group of animals, thriving in a wide variety of ecological systems and habitats. Most likely, it was the highly developed dental apparatus, which allows them to eat a variety of foods, that became the reason for the evolutionary success of multitubercles. Their fossilized remains, found on most continents, belong to different species: some of them apparently lived in trees, while others, reminiscent of modern gerbils, were probably adapted to exist in arid desert climates.
Changing Ecosystems
The existence of polytubercles spans a period of 215 million years, extending from the Late Triassic through the entire Mesozoic era to the Oligocene era Cenozoic era. This phenomenal success, unique among mammals and most terrestrial tetrapods, makes polytubercles the most successful group of mammals.Small animal ecosystems of the Jurassic period also included small lizards of a wide variety of species and even their aquatic forms.
Thrinadoxon (cynodont species). Its limbs protruded slightly to the sides, and were not located under the body, as in modern mammals.
They and the rarely encountered reptiles of the group of synapsids (“beast-like reptiles”), tritylodonts, who survived to this time, lived at the same time and in the same ecosystems as polytubercular mammals. Tritylodonts were numerous and widespread throughout the Triassic period, but, like other cynodonts, suffered greatly during the Late Triassic extinction event. They are the only group of cynodonts to survive into the Jurassic period. By appearance they, like multitubercular mammals, closely resembled modern rodents. That is, a significant part of the ecosystems of small animals of the Jurassic period consisted of animals resembling rodents: trilodonts and polytubercular mammals.
Polytuberculates were by far the most numerous and diverse group of mammals of the Jurassic period, but other groups of mammals existed at this time, including: morganacodonts (the oldest mammals), amphilestids (peramurids), amphitherids (amphitherids), tynodonts ( tinodontids) and docodonts.
All these small mammals looked like mice or shrews. Docodonts, for example, developed distinctive, wide molars well suited for chewing hard seeds and nuts. At the end of the Jurassic period, significant changes occurred at the other end of the size scale in the group of large bipedal predatory dinosaurs, theropods, represented at this time by allosaurs (AUosaurus - “strange lizards”). At the end of the Jurassic period, a group of theropods became isolated, called spinosaurids (“spiny or spiny lizards”). distinctive feature
which had a crest of long processes of the trunk vertebrae, which, perhaps, like the dorsal sail of some pelycosaurs, helped them regulate body temperature. Spinosaurids such as Siamosaurus (“lizard from Siam”), which reached a length of 12 m, along with other theropods shared the niche of the largest predators in the ecosystems of that time.
Bird-like dinosaurs
In Late Jurassic time, other types of theropods arose, very different from such huge, weighing up to 4 tons, predators as allosaurus. These were ornithominids - long-legged, long-necked, small-headed, toothless omnivores, strikingly reminiscent of modern ostriches, which is why they got their name “bird imitators”.The earliest ornithominid, Elaphrosaums ("light lizard"), from the Late Jurassic deposits of North America had light, hollow bones and a toothless beak, and its limbs, both hind and forelimbs, were shorter than those of later Cretaceous ornithominids, and, accordingly, it was a slower animal.
Another ecologically important group of dinosaurs that arose in the Late Jurassic are the nodosaurs, four-legged dinosaurs with massive, shell-covered bodies, short, relatively thin limbs, a narrow head with an elongated snout (but with massive jaws), small leaf-shaped teeth, and a horny beak. Their name (“knobby lizards”) is associated with the bony plates covering the skin, protruding processes of the vertebrae and growths scattered across the skin, which served as protection from attacks by predators. Nodosaurs became widespread only in the Cretaceous period, and in the Late Jurassic they, along with huge tree-eating sauropods, were only one of the elements of a community of herbivorous dinosaurs that served as prey for a number of huge predators.
The Jurassic period is the middle of the Mesozoic era. This piece of history is primarily famous for its dinosaurs, it was very good time
for all living things. During the Jurassic period, for the first time, reptiles dominated everywhere: in water, on land and in the air.
The Jurassic period lasted from 213 to 144 million years ago. At the very beginning of the Jurassic period, the climate throughout the Earth was dry and warm. All around were deserts. But later they began to be saturated with moisture by heavy rains. And the world became greener, lush vegetation began to bloom.
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. Throughout the northern hemisphere, the vegetation was quite monotonous. But already starting from the middle of the Jurassic period, about 170-165 million years ago, two (conditional) plant belts were formed: northern and southern. In the northern plant belt ginkgo and herbaceous ferns predominated. 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. The habitats of ferns and cordaites of the Jurassic period are now occupied by tropical forests, consisting mainly of cycads. Cycads are a class of gymnosperms that dominated the green cover of the Jurassic Earth. Nowadays they are found here and there 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 they were even initially identified as palm trees in the plant system.
In the Jurassic period, ginkgos were also common - deciduous (which is unusual for gymnosperms) trees with an oak-like crown and small fan-shaped leaves. Only one species has survived to this day - Ginkgo biloba. The first cypress and, possibly, spruce trees appear precisely during the brisk period. Coniferous forests Jurassic period were similar to modern ones.
During the Jurassic period, a temperate climate established on Earth. Even arid zones were rich in vegetation. Such conditions were ideal for the reproduction of dinosaurs. Among them are the lizard and ornithischians.
Lizards moved on four legs, had five toes on their feet, and ate plants. Most of them had 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 Jurassic dinosaurs there was a brachiosaurus that reached a length of 26 m and weighed 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. 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. Brontosaurus weighed about 30 tons and was over 20 in length. Lizard-footed dinosaurs (sauropods) were the largest land animals known so far. All of them were herbivores. Until recently, paleontologists believed that such heavy creatures were forced to spend most of their lives in water. It was believed that on land his shin bones would “break” under the weight of the colossal carcass. However, the findings recent years(in particular, the remains of the legs) indicate that sauropods preferred to wander in shallow water; they also entered solid ground. Relative to body size, brontosaurs had an extremely small brain, weighing no more than a pound. There was an expansion in the area of the sacral vertebrae of the Brontosaurus spinal cord. Being much larger than the brain, it controlled the muscles of the hind limbs and tail.
Ornithischian dinosaurs are divided into bipeds and quadrupeds. Different in size and appearance, they fed mainly on vegetation, but predators also appeared among them.
Stegosaurs are herbivores. Stegosaurs are especially abundant in North America, where several species of these animals are known, reaching a length of 6 m. The back was steeply convex, the height of the animal reached 2.5 m. The body was massive, although the stegosaurus moved on four legs, its forelimbs were much shorter rear On the back there were large bone plates in two rows that protected the spinal column. At the end of the short, thick tail, used by the animal for protection, there were two pairs of sharp spines. Stegosaurus was a vegetarian and had an exceptionally small head and correspondingly tiny brain, little more than walnut. Interestingly, the expansion of the spinal cord in the sacral region, associated with the innervation of the powerful hind limbs, was much larger in diameter than the brain.
Many scaly lepidosaurs appear - small predators with beak-like jaws.
Flying lizards first appeared in the Jurassic period. They flew using a leathery shell stretched between the long finger of the hand and the bones of the forearm. Flying lizards were well adapted to flight. They had light tube-shaped bones. The extremely elongated outer fifth digit of the forelimbs consisted of four joints. The first finger looked like a small bone or was completely absent. The second, third and fourth fingers consisted of two, rarely three bones and had claws. The hind limbs were quite developed. There were sharp claws at their ends. The skull of flying lizards was relatively large, usually elongated and pointed. In old lizards, the cranial bones fused and the skulls became similar to the skulls of birds. The premaxillary bone sometimes grew into an elongated toothless beak. Toothed lizards had simple teeth and sat in recesses. The largest teeth were in the front. Sometimes they stuck out to the side. This helped the lizards catch and hold prey. The spine of animals consisted of 8 cervical, 10-15 dorsal, 4-10 sacral and 10-40 caudal vertebrae. The chest was wide and had a high keel. The shoulder blades were long pelvic bones have grown together. The most typical representatives of flying lizards are pterodactyl and rhamphorhynchus.
Pterodactyls were in most cases tailless, varying in size - from the size of a sparrow to a crow. They had wide wings and a narrow skull elongated forward with a small number of teeth in the front. Pterodactyls lived in large flocks on the shores of the lagoons of the Late Jurassic Sea. During the day they hunted, and at nightfall they hid in trees or rocks. The skin of pterodactyls was wrinkled and bare. They ate mainly fish, sometimes sea lilies, mollusks, and insects. In order to fly, pterodactyls were forced to jump from cliffs or trees.
Rhamphorhynchus had long tails, long narrow wings, a large skull with numerous teeth. Long teeth of varying sizes curved forward. The lizard's tail ended in a blade that served as a rudder. Rhamphorhynchus could take off from the ground. They settled on the banks of rivers, lakes and seas, feeding on insects and fish.
Flying lizards lived only in the Mesozoic era, and their heyday occurred in the Late Jurassic period. Their ancestors were, apparently, extinct ancient reptiles pseudosuchians. Long-tailed forms appeared earlier than short-tailed ones. At the end of the Jurassic period they became extinct.
It should be noted that flying lizards were not the ancestors of birds and bats. Flying lizards, birds and the bats each originated and developed in its own way, and there are no close family ties between them. The only thing they have in common is the ability to fly. And although they all acquired this ability due to changes in the forelimbs, the differences in the structure of their wings convince us that they had completely different ancestors.
The seas of the Jurassic period were inhabited by dolphin-like reptiles - ichthyosaurs. They had a long head, sharp teeth, large eyes surrounded by a bony ring. The length of the skull of some of them was 3 m, and the length of the body was 12 m. The limbs of ichthyosaurs consisted of bone plates. The elbow, metatarsus, hand and fingers differed little from each other in shape. About a hundred bone plates supported the wide flipper. The shoulder and pelvic girdles were poorly developed. There were several fins on the body. Ichthyosaurs were viviparous animals.
Plesiosaurs lived alongside ichthyosaurs. Appearing in the Middle Triassic, they reached their peak already in the Lower Jurassic; in the Cretaceous they were common in all seas. They were divided into two main groups: long-necked with a small head (plesiosaurs proper) and short-necked with a rather massive head (pliosaurs). The limbs turned into powerful flippers, which became the main organ of swimming. More primitive Jurassic pliosaurs come mainly from Europe. A plesiosaur from the Lower Jurassic reached a length of 3 m. These animals often went ashore to rest. Plesiosaurs were not as agile in water as pliosaurs. This deficiency was to a certain extent compensated for by the development of a long and very flexible neck, with the help of which plesiosaurs could grab prey with lightning speed. They ate mainly fish and shellfish.
During the Jurassic period, new genera of fossil turtles appeared, and at the end of the period, modern turtles appeared.
Tailless frog-like amphibians lived in fresh water bodies.
There were a lot of fish in the Jurassic seas: bony fish, stingrays, sharks, cartilaginous fish, and ganoid fish. They had an internal skeleton made of flexible cartilaginous tissue impregnated with calcium salts: a dense scaly bone cover that protected them well from enemies, and jaws with strong teeth.
Of the invertebrates in the Jurassic seas, there were ammonites, belemnites, sea lilies. However, in the Jurassic period there were much fewer ammonites than in the Triassic. Jurassic ammonites differ from Triassic ammonites in their structure, with the exception of phyloceras, which did not change at all during the transition from the Triassic to the Jurassic. Certain groups of ammonites have preserved mother-of-pearl to this day. Some animals lived in the open sea, others inhabited bays and shallow inland seas.
Cephalopods - belemnites - swam in whole schools in the Jurassic seas. Along with small specimens, there were real giants - up to 3 m long.
Remains of belemnite internal shells, known as “devil's fingers,” are found in Jurassic sediments.
In the seas of the Jurassic period we received significant development also bivalves, especially those belonging to the oyster family. They begin to form oyster banks. Significant changes are undergoing sea urchins, settled on the reefs. Along with the round forms that have survived to this day, there lived bilaterally symmetrical, irregularly shaped hedgehogs. Their body was stretched in one direction. Some of them had a jaw apparatus.
The Jurassic seas were relatively shallow. Rivers brought muddy water into them, delaying gas exchange. The deep bays were filled with rotting remains and silt containing, a large number of hydrogen sulfide. That is why in such places the remains of animals brought in are well preserved. sea currents or waves.
Many crustaceans appear: barnacles, decapods, phyllopods, freshwater sponges, among insects - dragonflies, beetles, cicadas, bugs.
Deposits of coal, gypsum, oil, salt, nickel and cobalt are associated with Jurassic deposits.
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Jurassic period, Jurassic period movie
Jurassic period (Yura) - 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. Sediment complex ( rocks), corresponding to a given age, is called Jurassic system. different regions planets, 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 variety of conditions.
- 1 Jurassic Division
- 1.1 Geological events
- 1.2 Climate
- 1.3 Vegetation
- 1.4 Marine organisms
- 1.5 Land animals
- 2 Notes
- 3 Literature
- 4 Links
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 | |
| Upper (malm) | Tetonian | 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 in accordance with IUGS as of January 2015 | ||||
Geological events
213-145 million years ago, the single supercontinent Pangea began to break up into separate continental blocks. Shallow seas formed between them.
Climate
The climate in the Jurassic period was humid and warm (and by the end of the period - arid in the equator region).
Vegetation
Drooping cycad (Cycas revoluta) is one of the cycads growing todayGinkgo biloba (Ginkgo biloba). Botanical illustration from Siebold and Zuccarini's book Flora Japonica, Sectio Prima, 1870
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.
The conifers were very diverse, similar to modern pines and cypresses, which flourished at that time not only in the tropics, but had already mastered temperate zone. The ferns gradually disappeared.
Marine organisms
Leedsichthys and LiopleurodonCompared 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. Folds up new type reef communities, approximately the same as what exists now. It is based on six-rayed corals that appeared in the Triassic.
Land animals
Reconstruction of Archeopteryx,Oxford University Museum
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. There were free fingers on his wings (from modern birds they are preserved only in hoatzin chicks).
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), dominant on land, lived in forests, lakes, and swamps. The range of differences between them is so great that family ties between their species are established with great difficulty. There were dinosaurs ranging in size from a cat to a whale. Different types dinosaurs could walk on two or four limbs. Among them were both predators and herbivores. Of the latter, the Jurassic period saw the heyday of sauropods - diplodocus, brachiosaurs, apatosaurs, and camarasaurs. Sauropods were hunted by other lizard-hipped dinosaurs, namely large theropods.
Brachiosaurus
Ceratosaurus
Pseudotribos
Notes
- International Stratigraphic Chart (January 2013 version) on the website of the International Commission on Stratigraphy
Literature
- Iordansky N. N. Development of life on earth. - M.: Education, 1981.
- Karakash N.I. Jurassic system and period // encyclopedic Dictionary Brockhaus and Efron: in 86 volumes (82 volumes and 4 additional). - St. Petersburg, 1890-1907.
- Koronovsky N.V., Khain V.E., Yasamanov N.A. Historical geology: Textbook. - M.: Academy, 2006.
- Ushakov S.A., Yasamanov N.A. Continental drift and climates of the Earth. - M.: Mysl, 1984.
- Yasamanov N.A. Ancient climates of the Earth. - L.: Gidrometeoizdat, 1985.
- Yasamanov N.A. Popular paleogeography. - M.: Mysl, 1985.
Links
- Jurassic.ru - Site about the Jurassic period, a large library of paleontological books and articles.
| ← | P A l e O h O th | Mesozoic (251-65 million years ago) | TO A th n O h O th | → | ||
|---|---|---|---|---|---|---|
| ← | Triassic (251-199) | (199-145) | Cretaceous period (145-65) | → | ||
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Jurassic Period Information About
, conglomerates formed in a variety of conditions.
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 | |
| Yura | Upper (malm) |
Tetonian | 152,1-145,0 | |
| Kimmeridge | 157,3-152,1 | |||
| Oxford | 163,5-157,3 | |||
| Average (dogger) |
Callovian | 166,1-163,5 | ||
| Bathian | 168,3-166,1 | |||
| Bayocian | 170,3-168,3 | |||
| Aalensky | 174,1-170,3 | |||
| Lower (lias) |
Toarsky | 182,7-174,1 | ||
| Pliensbachian | 190,8-182,7 | |||
| Sinemyursky | 199,3-190,8 | |||
| Hettangian | 201,3-199,3 | |||
| Triassic | Upper | Rhetic | more | |
| Divisions are given according to IUGS as of April 2016 | ||||
Geological events
213-145 million years ago, the single supercontinent Pangea began to break up into separate continental blocks. Shallow seas formed between them.
Climate
The climate in the Jurassic period was humid and warm (and by the end of the period - arid in the equator region).
Vegetation
During the Jurassic, vast areas were covered with lush vegetation, primarily diverse forests. They mainly consisted of ferns and gymnosperms.
Land animals
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 work "On the Origin of Species" and became a strong argument in favor of the theory of evolution - it was initially considered transitional form from reptiles to birds (in fact, this was a dead-end branch of evolution, not directly related to real birds). Archeopteryx flew rather 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. During the Jurassic period, the division of mammals into monotremes, marsupials and placentals occurred.
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Notes
Literature
- Iordansky N. N. Development of life on earth. - M.: Education, 1981.
- Karakash N. I. ,. Jurassic system and period // Encyclopedic Dictionary of Brockhaus and Efron: in 86 volumes (82 volumes and 4 additional). - St. Petersburg. , 1890-1907.
- Koronovsky N.V., Khain V.E., Yasamanov N.A. Historical geology: Textbook. - M.: Academy, 2006.
- Ushakov S.A., Yasamanov N.A. Continental drift and climates of the Earth. - M.: Mysl, 1984.
- Yasamanov N.A. Ancient climates of the Earth. - L.: Gidrometeoizdat, 1985.
- Yasamanov N.A. Popular paleogeography. - M.: Mysl, 1985.
Links
- - Site about the Jurassic period, a large library of paleontological books and articles.
| ← | P A l e O h O th |
Mesozoic (252.2-66.0 million years ago) | TO A th n O h O th |
→ | ||
|---|---|---|---|---|---|---|
| ← | Triassic (252,2-201,3) |
Jurassic period (201,3-145,0) |
Cretaceous period (145,0-66,0) |
→ | ||
An excerpt characterizing the Jurassic period
The trees stood bare and featureless, lazily moving their drooping, thorny branches. Further behind them stretched the joyless, burnt-out steppe, getting lost in the distance behind a wall of dirty, gray fog... Many gloomy, drooping human beings restlessly wandered back and forth, senselessly looking for something, not paying any attention to the world around them, which, and however, it did not evoke the slightest pleasure so that one would want to look at it... The whole landscape evoked horror and melancholy, seasoned with hopelessness...“Oh, how scary it is here...” Stella whispered, shuddering. – No matter how many times I come here, I just can’t get used to it... How do these poor things live here?!
– Well, probably these “poor things” were too guilty once if they ended up here. Nobody sent them here - they just got what they deserved, right? – still not giving up, I said.
“But now you’ll look...” Stella whispered mysteriously.
A cave overgrown with grayish greenery suddenly appeared in front of us. And out of it, squinting, came a tall, stately man who in no way fit into this wretched, soul-chilling landscape...
- Hello, Sad! – Stella greeted the stranger affectionately. - So I brought my friend! She doesn't believe that good people can be found here. And I wanted to show you to her... You don’t mind, do you?
“Hello, dear...” the man answered sadly, “But I’m not that good to show off to anyone.” You're wrong...
Oddly enough, I actually immediately liked this sad man for some reason. He exuded strength and warmth, and it was very pleasant to be around him. In any case, he was in no way like those weak-willed, grief-stricken people who surrendered to the mercy of fate, with whom this “floor” was chock-full.
“Tell us your story, sad man...” Stella asked with a bright smile.
“There’s nothing to tell, and there’s nothing particularly to be proud of...” the stranger shook his head. - And what do you need this for?
For some reason, I felt very sorry for him... Without knowing anything about him, I was already almost sure that this man could not have done anything truly bad. Well, I just couldn’t!.. Stela, smiling, followed my thoughts, which she apparently really liked...
“Well, okay, I agree - you’re right!..” Seeing her happy face, I finally honestly admitted.
“But you don’t know anything about him yet, but with him everything is not so simple,” Stella said, smiling slyly and contentedly. - Well, please tell her, Sad...
The man smiled sadly at us and said quietly:
– I’m here because I killed... I killed many. But it was not out of desire, but out of need...
I was immediately terribly upset - he killed!.. And I, stupid, believed it!.. But for some reason I stubbornly did not have the slightest feeling of rejection or hostility. I clearly liked the person, and no matter how hard I tried, I couldn’t do anything about it...
- Is it really the same guilt - to kill at will or out of necessity? – I asked. – Sometimes people have no choice, do they? For example: when they have to defend themselves or protect others. I have always admired heroes - warriors, knights. I generally always adored the latter... Is it possible to compare simple murderers with them?
He looked at me for a long time and sadly, and then also quietly answered:
- I don’t know, dear... The fact that I am here says that the guilt is the same... But the way I feel this guilt in my heart, then no... I never wanted to kill, I just defended my land, I was a hero there... But here it turned out that I was just killing... Is this right? I think no...
- So you were a warrior? – I asked hopefully. - But then, this is a big difference– you defended your home, your family, your children! And you don’t look like a murderer!..
- Well, we are all not like the way others see us... Because they see only what they want to see... or only what we want to show them... And about the war - I also first just as you thought, you were even proud... But here it turned out that there was nothing to be proud of. Murder is murder, and it doesn’t matter how it was committed.
“But this is not right!..” I was indignant. - What happens then - a maniac-killer turns out to be the same as a hero?!.. This simply cannot be, this should not happen!
Everything inside me was raging with indignation! And the man sadly looked at me with his sad, gray eyes, in which understanding was read...
“A hero and a murderer take lives in the same way.” Only, probably, there are “extenuating circumstances”, since a person protecting someone, even if he takes a life, does so for a bright and righteous reason. But, one way or another, they both have to pay for it... And it’s very bitter to pay, believe me...
– Can I ask you how long ago you lived? – I asked, a little embarrassed.
- Oh, quite a long time ago... This is the second time I’m here... For some reason, my two lives were similar - in both of them I fought for someone... Well, and then I paid... And it’s always just as bitter ... – the stranger fell silent for a long time, as if not wanting to talk about it anymore, but then he quietly continued. – There are people who love to fight. I always hated it. But for some reason, life is returning me to the same circle for the second time, as if I was locked in this, not allowing me to free myself... When I lived, all our peoples fought among themselves... Some seized foreign lands - others they defended the lands. Sons overthrew fathers, brothers killed brothers... Anything happened. Someone accomplished unimaginable feats, someone betrayed someone, and someone turned out to be simply a coward. But none of them even suspected how bitter the payment would be for everything they had done in that life...
– Did you have family there? – to change the subject, I asked. - Were there children?
- Certainly! But that was already so long ago!.. They once became great-grandfathers, then they died... And some are already living again. That was a long time ago...
“And you’re still here?!..” I whispered, looking around in horror.
I couldn’t even imagine that he had been existing here like this for many, many years, suffering and “paying” his guilt, without any hope of leaving this terrifying “floor” even before the time came for him to return to the physical Earth!.. And there he will again have to start all over again, so that later, when his next “physical” life ends, he will return (perhaps here!) with a whole new “baggage”, bad or good, depending on how he will live his “next” earthly life... And he could not have any hope of freeing himself from this vicious circle (be it good or bad), since, having begun his earthly life, each person “dooms” himself to this endless, an eternal circular “journey”... And, depending on his actions, returning to the “floors” can be very pleasant, or very scary...
Page 3 of 4
Jurassic period- This is the second (middle) period of the Mesozoic era. It begins 201 million years before our times, lasts 56 million years and ends 145 million years ago (according to other sources, the duration of the Jurassic period is 69 million years: 213 - 144 million years). Named after the mountains Yura, in which its sedimentary layers were first identified. Notable for the widespread proliferation of dinosaurs.
Main subsections of the Jurassic period, its geography and climate
In accordance with the classification adopted by the International Union of Geological Sciences, The Jurassic period is divided into three divisions- Lower - Leyas (stages - Hettangian, Sinemurian, Pliensbachian, Toarcian), Middle - Dogger (stages - Aalenian, Bayocian, Bathian, Callovian) and Upper Small (stages - Oxfordian, Kimmeridge, Tithonian).
| Jurassic period | Departments | tiers |
| Leias (Lower) | Hettangian | |
| Sinemyursky | ||
| Pliensbachian | ||
| Toarsky | ||
| Dogger (Medium) | Aalensky | |
| Bayocian | ||
| Bathian | ||
| Callovian | ||
| Small (Upper) | Oxford | |
| Kimmeridge | ||
| Tetonian |
During this period, the division of Pangea into component blocks - continents - continued. Upper Laurentia, which later became North America and Europe, finally separated from Gondwana, which again began to move south. As a result of this, the connection between global continents was disrupted, which had an important impact on the further evolution and development of flora and fauna. The differences that arose at that time are sharply expressed to this day.
The Tethys Sea, which expanded even more as a result of the divergence of the continents, now occupied most of modern Europe. It originated from the Iberian Peninsula and, crossing the south and southeast of Asia diagonally, came out in Pacific Ocean. Most of present-day France, Spain and England were under his warm waters. On the left, as a result of the separation of the North American section of Gondwanaland, a depression began to emerge, which in the future became the Atlantic Ocean.
With the beginning of the Jurassic era average temperature on the globe began to decline little by little, and therefore in the lower part Jurassic climate was close to temperate - subtropical. But closer to the middle, the temperature began to rise again, and by the beginning of the Cretaceous period the climate became a greenhouse.
Ocean levels rose and fell slightly throughout the Jurassic, but the average sea level height was an order of magnitude higher than in the Triassic. As a result of the divergence of continental blocks, a great many small lakes were formed, in which both plant and animal life began to develop and progress very quickly, so that the quantitative and qualitative level of flora and fauna of the Jurassic period soon caught up and surpassed the Permian level to the point of worldwide mass extinction.
Sedimentation
With a drop in temperature throughout the earth, multiple precipitation began to fall abundantly, which contributed to the advancement of vegetation, and then the animal world, into the depths of the continents, which is due to Jurassic sedimentation. But the formation products are the most intense for this period earth's crust under the influence of continental shifts, and as a consequence - volcanic and other seismic activity. These are various igneous, clastic rocks. There are large deposits of shale, sand, clay, conglomerates, and limestone.
The warm and stable climate of the Jurassic period greatly contributed to the rapid development, formation and evolutionary improvement of both previous and new life forms.
(Fig. 1) rose to a new level in comparison with the sluggish Triassic, which did not particularly shine with varieties.
, both in the distant oceanic depths and in the warm coastal and inland seas.
Belemnites reached unprecedented development in the Jurassic era. They gathered in flocks and plowed the depths of the sea in search of unwary prey. Some of them at that time reached three meters in length. The remains of their shells, nicknamed “devil’s fingers” by scientists, are found almost everywhere in Jurassic sediments.
There were also numerous bivalve mollusks belonging to the oyster species. At that time, they began to form peculiar oyster banks. Numerous sea urchins, which abundantly populated reef areas at that time, also received an impetus for their development. Some of them have successfully survived to this day. But many, such as elongated hedgehogs of irregular shapes that had a jaw apparatus, became extinct. Insects also took a big step in their development. Their visual, flying and other devices were increasingly improved. More and more varieties appeared among barnacles, decapods, and leaf-footed crustaceans; most freshwater sponges and caddisflies multiplied and evolved. Ground insects of the Jurassic period
were replenished with new varieties of dragonflies, beetles, cicadas, bugs, etc. Along with the emergence of a huge number of flowering plants, a large number of pollinating insects began to appear, feeding on flower nectar. greatest development in the Jurassic era it was the reptiles that reached - dinosaurs. By the middle of the Jurassic period, they completely took over all land areas, displacing or destroying their reptilian predecessors, from whom they descended, in the pursuit of food.
IN sea depths already at the beginning of the Jurassic period reigned supreme dolphin-like ichthyosaurs. Their long heads had strong, elongated jaws studded with rows of sharp teeth, and large, highly developed eyes were framed by bone-plate rings. By the middle of the period they had become real giants. The length of the skull of some ichthyosaurs reached 3 meters, and the body length exceeded 12 meters. The limbs of these aquatic reptiles evolved under the influence of underwater life and consisted of simple bony plates. Elbows, metatarsals, hands and fingers ceased to differ from each other; one huge flipper supported more than a hundred bone plates of various sizes. The shoulder and pelvic girdles became underdeveloped, but this was not necessary, since mobility in aquatic environment they were provided with additionally grown powerful fins.
Another reptile that seriously and permanently settled in the depths of the sea was plesiosaur. They, like ichthyosaurs, arose in the seas during the Triassic period, but in the Jurassic period they branched into two varieties. Some had a long neck and a small head (plesiosaurs), others had an order of magnitude larger head, and a much shorter neck, which made them look more like underdeveloped crocodiles. Both of them, unlike ichthyosaurs, still needed rest on land, and therefore often crawled onto it, becoming the prey of land giants, such as, for example, a tyrannosaurus or herds of smaller predatory reptiles. Very agile in the water, on land they were clumsy fur seals our time. Pliosaurs were much more maneuverable in the water, but what plesiosaurs lacked in agility they made up for with their long necks, which allowed them to instantly grab prey no matter what position their bodies were in.
All kinds of fish species multiplied unusually in the Jurassic period. The water depths were literally teeming with a motley variety of coral ray-finned, cartilaginous and ganoids. Sharks and rays were also diverse, still constituting, due to their extraordinary agility, speed and agility developed over hundreds of millions of years of evolution, Jurassic underwater reptile predators. Also during this period, many new varieties of turtles and toads appeared.
But the terrestrial diversity of reptile dinosaurs was truly remarkable.
(Fig. 2) were from 10 centimeters to 30 meters in height. Many of them were simple harmless herbivores, but often there were also ferocious predators.
Rice. 2 - Jurassic Dinosaurs One of the largest herbivorous dinosaurs was brontosaurus
(now - Apatosaurus). Its body weighed 30 tons, its length from head to tail reached 20 meters. And despite the fact that its height at the shoulders reached only 4.5 meters, with the help of its neck, which reached a length of 5-6 meters, they perfectly ate up tree foliage. But most huge dinosaur of that era, as well as the absolute champion among all animals of the Earth of all times, was a 50-ton herbivore brachiosaurus
. With a body length of 26 m, he had such a long neck that when it stretched upward, his small head was 13 meters above the ground. To feed itself, this huge reptile needed to consume up to 500 kg of green mass every day. It is noteworthy that with such truly gigantic body sizes, his brain weighed no more than 450 grams. It is appropriate to say a few words about predators, of which there were also many in the Jurassic period. The most gigantic and dangerous predator Jurassic is considered 12 meters tyrannosaurus , but as scientists have proven, this predator was more opportunistic in its views on food. He rarely hunted, often preferring carrion. But they were truly dangerous allosaurs . With a height of 4 meters and a length of 11 meters, these reptile predators hunted prey that was many times larger than them in weight and other parameters. Often they, huddled in a herd, attacked such herbivorous giants
era, like Camarasaurus (47 tons) and the aforementioned Apatosaurus. We came across more small predators
In view of the ever-increasing danger from predatory individuals, evolution has awarded some herbivorous individuals with formidable elements of defense. For example, such a herbivorous dinosaur as centrosaurus was endowed with elements of protection in the form of huge sharp spikes on the tail and sharp plates along the ridge. The spikes were so large that with a strong blow, the Kentrosaurus would have pierced through a predator such as a Velociraptor or even a Dilophosaurus.
For all that, the animal world of the Jurassic period was carefully balanced. The population of herbivorous lizards was regulated by predatory lizards, predators were restrained by many smaller predators and aggressive herbivores, like stegosaurs. Thus, the natural balance was maintained for many millions of years, and what contributed to the extinction of dinosaurs in Cretaceous period it is still not known.
By the mid-Jurassic period, the airspace was filled with many flying dinosaurs such as pterodactyls and other pterosaurs. They glide quite skillfully in the air, but in order to take to the skies, they needed to climb to impressive heights. These, for the most part, were not very mobile specimens of ancient mammals, but from the air they could very successfully track and attack prey in a pack method. Smaller representatives of flying dinosaurs preferred to make do with carrion.
In Jurassic sediments, the remains of a fledgling Archeopteryx lizard were found, which for a long time considered by scientists to be the ancestor of birds. But, as it was recently scientifically proven, this species of lizards was a dead end. Birds evolved mainly from other species of reptiles. Archeopteryx had a long feathered tail, jaws studded with small teeth, and the feathered wings had developed fingers, with the help of which the animal grabbed branches. Archeopteryx flew poorly, mainly gliding from branch to branch. Basically, they preferred to climb tree trunks, digging into their bark and branches with the help of sharp curved claws. It is noteworthy that in our time only the chicks of the hoatzin bird have fingers on their wings.
The first birds, represented by small dinosaurs, jumped high either in an attempt to reach insects fluttering in the sky, or in order to escape from predators. In the process of evolution, they became more and more feathered, their jumps became longer and longer. During the jumping process, the future birds helped themselves more and more intensively by waving their forelimbs. Over time, their now wings, and not just forelimbs, acquired more and more powerful muscles, and the structure of their bones became hollow, as a result of which total weight birds became much easier. And all this led to the fact that by the end of the Jurassic period, the air space of the Jurassic, along with pterosaurs, was plowed by a large number of all kinds of ancient birds.
During the Jurassic period, small mammals also actively reproduced. But still they were not allowed to express themselves widely, since the ubiquitous power of dinosaurs was too overwhelming.
Since, during the process of climate change, the vast deserts of the Triassic began to be abundantly irrigated by precipitation, this created the preconditions for the advancement of vegetation further into the continents, and closer to the middle of the Jurassic period, almost the entire surface of the continents was covered with lush vegetation.
All low-lying places are abundantly overgrown with ferns, cycads and coniferous thickets. The sea coasts were occupied by araucarias, thujas and, again, cycads. Also, vast land masses were occupied by ferns and horsetails. Despite the fact that by the beginning of the Jurassic period the vegetation on the continents of the northern hemisphere was relatively uniform, by the middle of the Jurassic two already established and strengthened main belts of vegetation massifs were formed - northern and southern.
Northern belt was notable for the fact that at that time it was formed mainly by ginkgo plants mixed with herbaceous ferns. With all that half all vegetation northern latitudes Jurassic period consisted of varieties of ginkgo, today only one species of these plants has miraculously survived.
Southern belt were mainly cycads and tree ferns. At all Jurassic plants(Fig. 3) more than half still consisted of various ferns. Horsetails and mosses of those times were almost no different from today. In those places where cordaite and ferns grew en masse during the Jurassic period, this moment tropical cycad jungle grows. Of the gymnosperms, cycads were the most common in the Jurassic. Nowadays they can be found only in tropical and subtropical zones. It was these, with their crowns reminiscent of modern palm trees, that most herbivorous dinosaurs fed on.
Rice. 3 - Plants of the Jurassic period
In the Jurassic period northern latitudes Deciduous ginkgos began to appear for the first time. And in the second half of the period, the first spruce and cypress trees appeared. Jurassic coniferous forests were very similar to modern ones.
Minerals of the Jurassic period
The most pronounced mineral resources dating back to the Jurassic period are European and North American chromite deposits, Caucasian and Japanese copper pyrite deposits, and Alpine deposits manganese ores, tungsten ores of the Verkhoyansk-Chukotka region, Transbaikalia, Indonesia, and the North American Cordillera. Also to this era can be attributed deposits of tin, molybdenum, gold and other rare metals scattered throughout, formed in the late Cimmerian era and thrown to the surface as a result of granitoid mechanisms associated with the separation of continents that took place at the end of the Jurassic period. Iron ore deposits are numerous and widespread. There are uranium ore deposits on the Colorado Plateau.