Geological period. Neogene period. Triassic. Jurassic period. Jurassic period Jurassic period animals and plants
Our planet is several billion years old, and man appeared on it not so long ago. And millions of years ago, completely different creatures dominated the Earth - powerful, fast and huge. Of course, we are talking about dinosaurs that inhabited almost the entire surface of the planet many centuries ago. The number of species of these animals is quite large, and it can be said with certainty that the dinosaurs and the Jurassic world as a whole were the most diverse. And this era can be considered the heyday of the life of all flora and fauna.
Life is everywhere
The Jurassic period took place 200-150 million years ago. Quite a hot climate is characteristic of that time. Dense vegetation, lack of snow and cold led to the fact that life on earth was everywhere: on land, in air and in water. The increased humidity of the air led to the violent growth of plants, which became the food of herbivores, which grew to gigantic sizes. But they, like smaller animals, served as food for predators, the diversity of which is quite interesting.
The level of the World Ocean was much higher than now, and the favorable climate led to a rich variety of life in the water. The shallow waters teemed with mollusks and small animals, which became food for large marine predators. Life in the air was no less intense. The flying dinosaurs of the Jurassic period - pterosaurs - have seized dominance in the sky. But in the same period, the ancestors of modern birds appeared, in the wings of which there were no leather membranes, but feathers were born.
herbivorous dinosaurs
The Jurassic era gave the world many large reptiles. Most of them reached fantastically gigantic sizes. The largest dinosaur of the Jurassic period - diplodocus, which lived on the territory of the modern United States, reached a length of 30 meters and weighed almost 10 tons. It is noteworthy that the animal ate not only plant foods, but also stones. This was necessary so that small pebbles rubbed vegetation and tree bark in the animal's stomach. After all, the teeth of diplodocus were very small, no larger than a human fingernail, and could not help the animal to thoroughly chew plant foods.
An equally large brachiosaurus had a mass exceeding the weight of 10 elephants, and reached 30 meters in height. This animal lived on the territory of modern Africa and fed on the leaves of coniferous trees and cycads. Such a giant easily absorbed almost half a ton of plant food per day and preferred to settle near water bodies.
An interesting representative of herbivores of this era - Kentrosaurus - lived on the territory of modern Tanzania. This dinosaur of the Jurassic period was interesting for its body structure. On the back of the animal there were large plates, and the tail was covered with large spikes that helped to fight off predators. The animal was about 2 meters in height and up to 4.5 meters in length. The Kentrosaurus weighed a little over half a ton, making it the most agile dinosaur.
jurassic
The diversity of herbivores leads to the emergence of a large number of predators, because nature always keeps a balance. The largest and bloodthirsty dinosaur of the Jurassic period, the Allosaurus, reached a length of almost 11 meters and a height of 4 meters. This predator with a weight of 2 tons hunted in the United States and Portugal and earned the title of the fastest runner.
He ate not only small animals, but, uniting in groups, hunted even very large prey, such as apatosaurs or camarasaurus. To do this, a sick or young individual was beaten off from the herd by common efforts, after which they were collectively devoured.
A fairly well-known dilophosaurus, which lived on the territory of modern America, reached three meters in height and weighed up to 400 kilograms.
A fast predator with characteristic crests on its head, a rather bright representative of that period, similar to tyrannosaurs. He hunted small dinosaurs, but in a pair or a flock he could also attack an animal that was much larger than him. Great maneuverability and speed allowed Dilophosaurus to catch even a fairly fast and miniature Scutellosaurus.
Marine life
Land is not the only place that dinosaurs settled, and the world of the Jurassic period in the water was also diverse and multifaceted. A prominent representative of that era was the plesiosaur. This waterfowl predatory lizard had a long neck and reached a length of up to 18 meters. The structure of the skeleton with a short but rather wide tail and powerful paddle-like fins allowed this predator to develop great speed and reign in the depths of the sea.
An equally interesting marine dinosaur of the Jurassic period is an ichthyosaur, similar to a modern dolphin. Its peculiarity was that, unlike other lizards, this predator gave birth to live cubs, and did not lay eggs. The ichthyosaur reached 15 meters in length and hunted smaller prey.
sky kings
By the end of the Jurassic period, small pterodactyl predators conquered the heavenly heights. The wingspan of this animal reached one meter. The body of the predator was small and did not exceed half a meter, the weight of an adult individual reached 2 kilograms. The predator could not take off, and before flying, he had to climb a rock or ledge. The pterodactyl ate fish, which he could see at a considerable distance. But he himself sometimes became a victim of predators, because on land he was quite slow and clumsy.
Another representative of the flying dinosaurs was rhamphorhynchus. Slightly larger than a pterodactyl, this predator weighed three kilograms and had a wingspan of up to two meters. Habitat - Central Europe. A feature of this winged dinosaur was a long tail. Sharp teeth and powerful jaws made it possible to catch slippery and wet prey, and the basis of the animal's diet was fish, shellfish and, surprisingly, small pterodactyls.
living world
The world in that era is striking in its diversity: far from the only population of the Earth at that time were dinosaurs. And animals of the Jurassic period of other classes were quite common. After all, it was then, thanks to good conditions, that turtles appeared in the form that we are now familiar with. Frog-like amphibians bred, which became food for small dinosaurs.
The seas and oceans teemed with many kinds of fish, such as sharks, rays, and other cartilaginous and bony ones. they are also belemnites, they were the lowest link in the food chain, but their multi-membered population supported life in the water. During this period, crustaceans appear, such as barnacles, phyllopods, and freshwater sponges.
Intermediate
The Jurassic period is notable for the appearance of bird ancestors. Of course, Archeopteryx was not that much like a modern bird, it was more like a miniraptor with feathers.
But a later ancestor, also known as Longipteryx, already resembled a modern kingfisher. Although birds for that era are a rather rare occurrence, they are the ones that give rise to a new round in the evolution of the animal world. The dinosaurs of the Jurassic period (the photo is presented above) died out long ago, but even now, looking at the remains of such giants, you are in awe of these giants.
160 million years ago, a rich plant world provided food for the giant sauropods that had arisen by this time, and also provided shelter for a huge number of small mammals and pangolins. Conifers, ferns, horsetails, tree ferns and cycads were widespread at this time.
A distinctive feature of the Jurassic period was the appearance and flourishing of giant sauropod 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 (with the exception of 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 largest size. They survived until the late Cretaceous, when the huge hadrosaurs ("duck-billed dinosaurs") began to dominate among terrestrial herbivores.
Outwardly, all sauropods looked similar to each other: with an extremely long neck, an even longer tail, a massive but relatively short body, four columnar legs and a relatively small head. In different species, 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 taller in the shoulder girdle than in the pelvic girdle, while contemporary diplodocus (Diplodocus - “double process”) were significantly lower, and at the same time their hips towered over their shoulders. In some species of sauropods, such as the Camarasaurus (Camarasaurus - "chamber lizard"), the neck was relatively short, only slightly longer than the body, while in others, such as diplodocus, it was more than twice as long as the body.
Teeth and diet
The superficial resemblance of sauropods masks the surprisingly wide variety of their tooth structure and hence feeding methods.
The diplodocus skull has helped paleontologists understand the dinosaur's way of feeding. The abrasion of the teeth indicates that he tore off the leaves either from below or from above himself.
Many books on dinosaurs used to mention "small, thin teeth" of sauropods, but it is now known that the teeth of some of them, such as Camarasaurus, were massive and strong enough to grind even very hard plant foods, while the long and thin ones, the pencil-like teeth of Diplodocus do indeed seem unable to withstand the considerable stress that comes from chewing hard plants.
diplodocus (Diplodocus). The long neck allowed him to "comb" food from the highest coniferous plants. It is believed that diplodocus lived in small herds and fed on tree shoots.
During the study of the teeth of diplodocus, carried out in recent years in England, an unusual deterioration of their lateral surfaces was discovered. This pattern of tooth abrasion gave clues to how these huge animals could have eaten. The side surface of the teeth could wear out only if something moved between them. Apparently, diplodocus used its teeth to tear apart bundles of leaves and shoots, acting as a comb, while its lower jaw could move slightly back and forth. Most likely, when the animal divided into strips of plants captured below, moving its head up and back, the lower jaw was shifted back (the upper teeth were located in front of the lower ones), and when it pulled the branches of tall trees located at the top down and back, it pushed the lower jaw forward (the lower teeth were in front of the upper ones).
Brachiosaurus probably used its shorter, slightly pointed teeth to pluck only high-lying leaves and shoots, since its vertical body orientation, due to its longer front legs, made it difficult to feed on plants growing low above the soil.
Narrow specialization
Camarasaurus, slightly smaller 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 nutritional 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 durable lower jaw, which indicates a better ability to grind solid plant food.The details of the anatomical structure of sauropods described above show that within the same ecological system (in the forests covering most of the land at that time), sauropods fed on various plant foods, obtaining it in different ways at different levels. This division by feeding strategy and type of food, which can still be seen in herbivore communities today, has been called "tropical sectioning."
Brachiosaurus (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 the sauropod-dominated ecosystems of the Late Jurassic is 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 none of the modern land animals requires such a huge amount of food as these giants.
Other end of the scale
Some sauropods that lived in the Jurassic reached fantastic sizes, for example, the supersaurus resembling a brachiosaurus (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 the land with tiny creatures hiding underground that did not belong to dinosaurs or even reptiles. The Jurassic period was the time of the existence of many numerous ancient mammals. These small, fur-covered, viviparous, and milk-feeding warm-blooded animals are called multi-lumpy because of the unusual structure of their molars: numerous, fused together cylindrical “tubercles” form uneven surfaces, perfectly adapted to grinding plant foods.The polytuberculates were the largest and most diverse group of mammals in the Jurassic and Cretaceous periods. These are the only omnivorous mammals of the 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. haramiids.
In the structure of the skull and teeth, the multituberculates were very reminiscent of today's rodents, they had two pairs of protruding incisors, giving them the appearance of a typical rodent. Behind the incisors was a toothless gap, followed by molars to the very end of the small jaws. However, the teeth closest to the incisors had an unusual structure. In fact, these were the first false-rooted (premolar) teeth with curved sawtooth edges.
Such an unusual structure of teeth in the process of evolution re-emerged in some of the modern marsupials, for example, in rat kangaroos in Australia, whose teeth are the same shape and are located in the same place in the jaw as the pseudo-rooted teeth of polytuberculates. When chewing food at the moment of jaw closure, multituberculates could shift the lower jaw back, moving these sharp sawtooth teeth across food fibers, and long incisors could be used to pierce dense plants or hard external skeletons of insects.
Lizard-hipped megalosaurus (Megalosaurus) and its cubs, overtaking the ornithischian Scelidosaurus (Scelidosaurus). Scelidosaurus is an ancient species of dinosaurs of the Jurassic period with unevenly developed limbs, reaching 4 m in length. Its dorsal shell helped protect against predators.
The combination of sharp front incisors, serrated blades, and chewing teeth means that the feeding apparatus of the multituberculates 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 various foods, that became the reason for the evolutionary success of the multituberculates. Their fossilized remains, found on most continents, belong to various species: some of them, apparently, lived in trees, while others, resembling modern gerbils, were probably adapted to existence in an arid desert climate.
Ecosystem change
The existence of multituberculates covers a period of 215 million years, stretching from the late Triassic through the entire Mesozoic era to the Oligocene era of the Cenozoic era. This phenomenal success, unique to mammals and most terrestrial tetrapods, makes the polytuberculates the most successful group of mammals.The ecosystems of small animals of the Jurassic also included small lizards of various 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 rare reptiles of the synapsid group (“animal reptiles”), the tritylodonts, who survived to this time, lived at the same time and in the same ecosystems as the multi-tuberous mammals. Tritylodonts were a numerous and widespread species throughout the Triassic period, but, like other cynodonts, suffered greatly during the Late Triassic extinction. This is the only group of cynodonts that survived from the Jurassic. In appearance, they, like multi-tuberous mammals, very much 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 multituberous mammals.
The multitubercular mammals were by far the most numerous and diverse group of mammals of the Jurassic period, but other groups of mammals also existed at this time, including: tinodontids) and docodonts (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, significant changes occurred at the other end of the size scale in a group of large bipedal predatory dinosaurs, theropods, represented at that time by allosaurs (AUosaurus - "strange lizards"). At the end of the Jurassic, a group of theropods became isolated, called spinosaurids (“spiky or spiked lizards”), whose distinguishing feature was a crest of long processes of the trunk vertebrae, which, perhaps, like the dorsal sail in some pelycosaurs, helped them regulate body temperature. Such spinosaurids as Siamosaurus ("lizard from Siam"), whose length reached 12 m, together with other theropods, shared the niche of the largest predators in the ecosystems of that time.
Spinosaurids had non-serrated teeth and elongated, less massive skulls compared to other theropods of that time. These structural features indicate that they differed in their way of feeding from theropods such as allosaurs, Eustreptospondylus ("strongly curved vertebrae") and ceratosaurus (Ceratosaurus - "horned lizard"), and most likely hunted other prey.
bird-like dinosaurs
In the late Jurassic, other types of theropods arose, very different from such huge, weighing up to 4 tons, predators, like allosaurs. They were ornithominids - long-legged, long-necked, small-headed, toothless omnivores strikingly reminiscent of modern ostriches, which is why they got their name "bird mimics".The very first ornithominid, Elaphrosaums ("light lizard"), from the Late Jurassic of North America, had light, hollow bones and a toothless beak, and its limbs, both hind and fore, 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, armored 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 bone plates covering the skin, protruding processes of the vertebrae and growths scattered over the skin, which served as protection against predator attacks. Nodosaurs became widespread only in the Cretaceous, and in the Late Jurassic, they, along with huge tree-eating sauropods, were only one element of the herbivorous dinosaur community 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 a very good time for all living things. During the Jurassic period, for the first time, reptiles ruled everywhere: in water, on land and in the air.
This period was named after a mountain range in Europe. The Jurassic period began about 208 million years ago. This period was more revolutionary than the Triassic. This revolutionism was with those estates that occurred with the earth's crust, because it was during the Jurassic period that the mainland of Pangea began to diverge. The climate has since become warmer and more humid. In addition, the level of water in the world's oceans began to rise. All this gave great opportunities for animals. Due to the fact that the climate became more favorable, plants began to appear on land. And corals began to appear in shallow waters.
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 heavy rains began to soak them with moisture. And the world became greener, lush vegetation began to flourish.
Ferns, conifers, and cycads formed extensive marshy forests. Araucaria, arborvitae, cicadas 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 rather 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. Ginkgo and herbaceous ferns predominated in the northern vegetation belt. In the Jurassic period, Ginkgoaceae were very widespread. Groves of ginkgo trees grew throughout the belt.
In the southern vegetation belt, cycads and tree ferns predominated.
Ferns of the Jurassic period have survived to this day in some parts of the wild. Horsetails and club mosses almost did not differ from modern ones. Jurassic period ferns and cordaites 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. Now they are found here and there in the tropics and subtropics. Dinosaurs roamed under the canopy of these trees. Outwardly, 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, ginkgo trees are 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 during the Jurassic period. The coniferous forests of the Jurassic period were similar to modern ones.
During the Jurassic period, a temperate climate was established on Earth. Even the arid zones were rich in vegetation. Such conditions were ideal for the reproduction of dinosaurs. Among them, lizards and ornithischians are distinguished.
Lizards moved on four legs, had five toes on their feet, and ate plants. Most of them had a long neck, a small head and a long tail. They had two brains: one small, 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, weighing about 50 tons. It had columnar legs, a small head, and a thick long neck. Brachiosaurs lived on the shores of the Jurassic lakes, 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 moved on four legs, the hind legs were longer than the front ones. Diplodocus spent most of its life in swamps and lakes, where it grazed and escaped from predators.
Brontosaurus was comparatively tall, had a large hump on its back and a thick tail. Chisel-shaped small teeth were densely located on the jaws of a small head. The brontosaurus lived in swamps, on the shores of lakes. Brontosaurus weighed about 30 tons and exceeded 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 the water. It was believed that on land, his tibia would "break" under the weight of a colossal carcass. However, the finds of recent years (in particular, footprints) indicate that sauropods preferred to roam in shallow water, and they also entered solid ground. In relation to body size, brontosaurs had an extremely small brain, weighing no more than a pound. In the region of the sacral vertebrae of the brontosaurus, there was an expansion of the spinal cord. Being much larger than the brain, it controlled the musculature of the hind limbs and tail.
Ornithischian dinosaurs are divided into bipedal and quadrupedal. Different in size and appearance, they fed mainly on vegetation, but predators also appear among them.
Stegosaurs are herbivores. Stegosaurus is especially abundant in North America, from 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, large bone plates rose in two rows, protecting the spinal column. At the end of the short, thick tail, used by the animal for defense, there were two pairs of sharp spikes. Stegosaurus was a vegetarian and had an exceptionally small head and a correspondingly tiny brain, little more than a walnut. Interestingly, the expansion of the spinal cord in the sacral region, associated with the innervation of powerful hind limbs, was much larger in diameter than the brain.
Many scaly lepidosaurs appear - small predators with beak-shaped jaws.
In the Jurassic period, flying lizards first appear. They flew with the help of 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 tubular bones. The extremely elongated outer fifth finger 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 strongly developed. They had sharp claws at their ends. The skull of flying lizards was relatively large, as a rule, elongated and pointed. In old lizards, the cranial bones fused and the skulls became similar to the skulls of birds. The premaxilla sometimes grew into an elongated toothless beak. Toothed lizards had simple teeth and sat in recesses. The largest teeth were in front. Sometimes they stick out to the side. This helped the lizards to 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, the pelvic bones were fused. The most characteristic representatives of flying lizards are pterodactyl and rhamphorhynchus.
Pterodactyls in most cases were tailless, different in size - from the size of a sparrow to a crow. They had wide wings and a narrow skull extended 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 in rocks. The skin of pterodactyls was wrinkled and bare. They ate mainly fish, sometimes sea lilies, mollusks, and insects. In order to take off, pterodactyls had to jump off rocks or trees.
Rhamphorhynchus had long tails, long narrow wings, a large skull with numerous teeth. Long teeth of various sizes arched forward. The lizard's tail ended in a blade that served as a rudder. Ramphorhynchus could take off from the ground. They settled on the banks of rivers, lakes and seas, fed on insects and fish.
Flying lizards lived only in the Mesozoic era, and their heyday falls on the late Jurassic period. Their ancestors were apparently extinct ancient reptiles pseudosuchia. The long-tailed forms appeared before the short-tailed ones. At the end of the Jurassic, they became extinct.
It should be noted that flying lizards were not the ancestors of birds and bats. Flying lizards, birds and bats originated and developed in their own ways, 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 a change 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 bone ring. The length of the skull of some of them was 3 m, and the body length was 12 m. The limbs of ichthyosaurs consisted of bone plates. Elbow, metatarsus, hand and fingers did not differ much in shape from each other. About a hundred bone plates supported a wide flipper. Shoulder and pelvic girdle were poorly developed. There were several fins on the body. Ichthyosaurs were viviparous animals.
Along with ichthyosaurs lived plesiosaurs. Appeared 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 fairly massive head (pliosaurs). The limbs turned into powerful flippers, which became the main organ of swimming. The more primitive Jurassic pliosaurs originate mainly from Europe. Plesiosaurus from the Lower Jura, reached a length of 3 m. These animals often came ashore to rest. Plesiosaurs were not as dexterous in water as pliosaurs. To a certain extent, this shortcoming was compensated by the development of a long and very flexible neck, with the help of which plesiosaurs could seize prey with lightning speed. They ate mainly fish and shellfish.
In the Jurassic period, new genera of fossil turtles appear, and at the end of the period, modern turtles.
Tailless frog-like amphibians lived in fresh water.
There were a lot of fish in the Jurassic seas: bony, rays, sharks, cartilaginous, ganoid. They had an internal skeleton made of flexible cartilaginous tissue impregnated with calcium salts: a dense bony scaly cover that protected them well from enemies, and jaws with strong teeth.
Of the invertebrates in the Jurassic seas, ammonites, belemnites, sea lilies were found. However, in the Jurassic period, there were much fewer ammonites than in the Triassic. The Jurassic ammonites also differ from the Triassic in their structure, with the exception of the phyloceras, which did not change at all during the transition from the Triassic to the Jura. Separate groups of ammonites have preserved mother-of-pearl to our time. Some animals lived in the open sea, others inhabited bays and shallow inland seas.
Cephalopods - belemnites - swam in whole flocks in the Jurassic seas. Along with small specimens, there were real giants - up to 3 m long.
The remains of internal shells of belemnites, known as "devil's fingers", are found in the sediments of the Jurassic period.
In the seas of the Jurassic period, bivalve mollusks, especially those belonging to the oyster family, also developed significantly. They start to form oyster jars. Significant changes are undergoing sea urchins that settled on 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. The rivers brought muddy water into them, delaying gas exchange. Deep bays were filled with decaying remains and silt containing a large amount of hydrogen sulfide. That is why in such places the remains of animals, carried by sea currents or waves, are well preserved.
Many crustaceans appear: barnacles, decapods, leaf-legged crayfish, freshwater sponges, among insects - dragonflies, beetles, cicadas, bedbugs.
Deposits of coal, gypsum, oil, salt, nickel and cobalt are associated with the Jurassic deposits.
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 mountains Yura, in which its sedimentary layers were first identified. Significant for the widespread flowering of dinosaurs.
The main subdivisions of the Jurassic period, its geography and climate
According to the classification adopted by the International Union of Geological Sciences, The Jurassic period is divided into three divisions- Lower - Leyas (stages - Gottangsky, Sinemursky, Plinsbakhsky, Toarsky), Middle - Dogger (levels - Aalensky, Bayossky, Batsky, Callovian) and Upper Small (levels - Oxford, Kimmeridgsky, Tithonian).
| Jurassic period | Departments | Tiers |
| Leyas (Lower) | Goettansky | |
| Sinemursky | ||
| Plinsbachsky | ||
| Toarian | ||
| Dogger (Medium) | Aalen | |
| Bayosian | ||
| Bath | ||
| Callovian | ||
| Small (Upper) | Oxford | |
| Kimmeridge | ||
| titonian |
In this period, the division of Pangea into constituent blocks - the continents - continued. Upper Laurentia, which later became North America and Europe, finally separated from Gondwana, which again began to shift south. As a result, the connection between the global continents was broken, which had an important impact on the further evolution and development of flora and fauna. The differences that originated at that time are sharply expressed to this day.
The Tethys Sea, expanded even more as a result of the separation of the continents, now occupied most of modern Europe. It originated from the Iberian Peninsula and, crossing the south and southeast of Asia diagonally, went out into the Pacific Ocean. Much of what is now France, Spain and England was under its warm waters. On the left, as a result of the separation of the North American sector of Gondwana, a depression began to emerge, which in the future became the Atlantic Ocean.
With the onset of the Jurassic, the average temperature on the globe gradually began to decrease, and therefore in the lower section Jurassic climate was close to moderate - subtropical. But closer to the middle, the temperature began to rise again, and by the beginning of the Cretaceous period, the climate became greenhouse.
The ocean level rose and fell slightly throughout the Jurassic, but the average sea level 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 the flora and fauna of the Jurassic period soon caught up and outstripped the level of the Permian to the point of global mass extinction.
sedimentation
With a drop in temperature, multiple precipitation began to fall abundantly throughout the earth, 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 most intense for this period are the products of the formation of the earth's crust under the influence of continental shifts, and as a result, volcanic and other seismic activity. These are various igneous, clastic rocks. Large deposits of shale, sand, clay, conglomerates, limestone.
The warm and stable climate of the Jurassic period greatly contributed to the rapid development, formation and evolutionary improvement of both old and new life forms. (Fig. 1) have risen to a new level compared to the sluggish, not especially shining varieties, the Triassic.
Rice. 1 - Jurassic Animals
The Jurassic seas were full of various marine invertebrates. Especially numerous were belemnites, ammonites, all kinds of sea lilies. And although there were an order of magnitude fewer ammonites in the Jurassic than in the Triassic, they mostly had a more developed body structure than their ancestors from the previous era, with the exception of the phyloceras, which did not change at all during the millions of years of transition from the Triassic to the Jurassic. It was at that time that many ammonites acquired their indescribable mother-of-pearl coating, which has survived to this day. Ammonites were found in large quantities, both in the distant oceanic depths and in coastal warm and inland seas.
Belemnites in the Jurassic era reached an unprecedented development. They huddled in flocks and plowed the depths of the sea in search of gaping prey. Some of them at that time reached three meters in length. The remains of their shells, nicknamed by scientists "devil's fingers" are found in the sediments of the Jurassic period almost everywhere.
Bivalve mollusks belonging to oyster varieties were also numerous. In that era, they began to form a kind of oyster jars. Numerous sea urchins, which abundantly inhabited reef areas at that time, also received an impetus in development. Some of them have successfully survived to our time. But many, such as hedgehogs of irregular shapes elongated along the length, which had a jaw apparatus, died out.
Insects have also taken a big step forward. Their visual, flying and other devices improved more and more. More and more varieties appeared among the barnacles, decapods, leaf-footed crustaceans, most of the freshwater sponges and caddisflies multiplied and evolved. Ground jurassic insects replenished with new varieties of dragonflies, beetles, cicadas, bedbugs, etc. Along with the emergence of a huge number of flowering plants, a large number of pollinating insects that feed on flower nectar began to appear.
But it was the reptiles that reached the greatest development in the Jurassic era - dinosaurs. By the middle of the Jurassic period, they completely took over all the land areas, displacing or destroying their reptilian predecessors, from which they originated, in pursuit of food.
In the depths of the sea, already at the beginning of the Jurassic period, reigned supreme dolphin-like ichthyosaurs. Their long heads had strong, oblong 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 turned into 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 bone plates. Elbows, metatarsus, hands and fingers ceased to differ from each other, one huge flipper supported more than a hundred bone plates of various sizes. The shoulder girdle, as well as the pelvic girdle, became underdeveloped, but this was not necessary, since additionally grown powerful fins provided them with mobility in the aquatic environment.
Another reptile that seriously and permanently settled in the depths of the sea was plesiosaur. They, like ichthyosaurs, originated in the seas as early as the Triassic period, but in the Jurassic period they branched into two varieties. Some had a long neck and a small head (plesiosaurs), while others had an order of magnitude larger head and a much shorter neck, which made them look more like underdeveloped crocodiles. Both, unlike ichthyosaurs, still needed to rest on land, and therefore often crawled out onto it, becoming the prey of land giants there, such as, for example, a tyrannosaurus rex or herds of smaller predatory reptiles. Very nimble in the water, on land they were the clumsy fur seals of our time. Pliosaurs were much more agile in the water, but what plesiosaurs lacked in agility was made up for by their long necks, thanks to which they instantly grabbed prey, no matter what position their body was in.
In the Jurassic period, all kinds of fish multiplied unusually. The water depths literally teemed with a motley variety of coral ray-finned, cartilaginous and ganoid. Sharks with stingrays were also diverse, which, due to their extraordinary agility, speed and agility, developed over hundreds of millions of years of evolution, still constituted Jurassic underwater reptile predators. Also during this period, many new varieties of turtles and toads appeared.
But the terrestrial variety of reptile dinosaurs was truly outstanding. (Fig. 2) were from 10 cm to 30 meters in height. Many of them were simple harmless herbivores, but often came across and ferocious predators.
Rice. 2 - Jurassic Dinosaurs
One of the largest herbivorous dinosaurs was brontosaurus(now Apatosaurus). His body weighed 30 tons, the length from head to tail reached 20 meters. And despite the fact that his height at the shoulders reached only 4.5 meters, with the help of a neck that reached a length of up to 5-6 meters, they perfectly ate tree foliage.
But the largest dinosaur of that era, as well as the absolute champion among all the animals of the Earth of all time, was a 50-ton herbivore. brachiosaurus. With a body length of 26 m, he had such a long neck that when it stretched up, his small head was 13 meters above the ground. To feed, this huge reptile needed to absorb up to 500 kg of green mass daily. It is noteworthy that with such a truly gigantic body size, 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 of the Jura is considered a 12-meter tyrannosaurus rex, 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 many times greater than them in terms of weight and other parameters. Often they, having huddled in a herd, attacked such herbivorous giants of that era as Camarasaurus (47 tons) and the aforementioned Apatosaurus.
Smaller predators also came across, for example, such as 3-meter dilophosaurs, weighing only 400 kg, but straying into a flock, attacking even larger predators.
In view of the ever-increasing danger from predatory individuals, evolution has rewarded some herbivorous individuals with formidable elements of protection. For example, such a herbivorous dinosaur as Kentrosaurus 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 such a predator as a Velociraptor or even a Dilophosaurus.
For all that, the animal world of the Jurassic period was carefully balanced. The herbivorous lizard population was controlled by predatory lizards, predators were kept in check by many smaller predators and aggressive herbivores like stegosaurs. Thus, the natural balance was maintained for many millions of years, and what caused the extinction of dinosaurs in the Cretaceous period is still not known.
By the middle of the 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 need to climb imposing hills. These, for the most part, were not very mobile specimens of ancient mammals, but from the air they could very successfully track down and attack prey in a flocking manner. Smaller representatives of flying dinosaurs preferred to make do with carrion.
In the sediments of the Jurassic period, the remains of a fledged lizard Archeopteryx were found, which for a long time was considered by scientists to be the ancestor of birds. But, as recently scientifically proven, this variety of lizards was a dead end. Birds evolved mainly from other varieties of reptiles. Archeopteryx had a long feathered tail, jaws studded with small teeth, and feathered wings had developed fingers, with which the animal grabbed branches. Archeopteryxes flew poorly, mainly gliding from branch to branch. Basically, they preferred to climb tree trunks, digging into their bark and branches with sharp curved claws. It is noteworthy that in our time, fingers on the wings remained only in the chicks of the hoatzin bird.
The first birds, in the form of small dinosaurs, jumped high either in their attempts to reach out for insects fluttering in the sky, or in order to escape from predators. In the process of evolution, they were increasingly overgrown with plumage, their jumps became longer and longer. In the process of jumping, future birds helped themselves more and more intensively, 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 the overall weight of the birds became much lighter. And all this led to the fact that by the end of the Jurassic period, along with pterosaurs, a large number of all kinds of ancient birds plowed the airspace of the Jura.
In the Jurassic period, small mammals also actively multiplied. But still, they were not allowed to express themselves in breadth, because the ubiquitous power of dinosaurs was too overwhelming.
Since, in the process of climate change, the vast deserts of the Triassic began to be abundantly irrigated with precipitation, this created the prerequisites for the advancement of vegetation even deeper into the continents, and closer to the middle of the Jurassic, almost the entire surface of the continents was covered with lush vegetation.
All low-lying places are abundantly overgrown with ferns, cicadas and coniferous thickets. The coasts of the seas were occupied by araucaria, thuja and, again, cicadas. 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 main belts of plant masses, already established and strengthened, were formed - the 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 is half the whole vegetation northern latitudes jurassic consisted of Ginkgo varieties, today only one species of these plants has miraculously survived.
Southern belt were mainly cycads and tree ferns. Generally Jurassic period plants(Fig. 3) more than half still consisted of various ferns. Horsetails and club mosses of those times almost did not differ from the current ones. In those places where cordaite and ferns grew massively during the Jurassic, tropical cycad jungles are currently growing. Of the gymnosperms, cycads were the most common in the Jurassic. Today they can be found only in tropical and subtropical zones. It was them, reminiscent of modern palm trees with their crowns, that most herbivorous dinosaurs ate.
Rice. 3 - Plants of the Jurassic period
In the Jurassic period, deciduous Ginkgoaceae first began to appear in the northern latitudes. And in the second half of the period, the first spruce and cypress trees appeared. The coniferous forests of the Jura looked very much like modern ones.
Minerals of the Jurassic period
The most pronounced minerals related to the Jurassic period are European and North American chromite deposits, Caucasian and Japanese copper-pyrite deposits, Alpine deposits of manganese ores, tungsten ores of the Verkhoyansk-Chukotka region, Transbaikalia, Indonesia, North American Cordilleras. Also to this era can be attributed deposits of tin, molybdenum, gold and other rare metals scattered everywhere, formed in the late Cimmerian era and thrown to the surface due to granitoid mechanisms associated with the separation of the continents that took place at the end of the Jurassic period. Numerous and ubiquitous iron ore deposits. There are deposits of uranium ores on the Colorado Plateau.
Jurassic period (Jurassic)- the middle (second) period of the Mesozoic era. It began 201.3 ± 0.2 Ma ago and ended 145.0 Ma ago. It continued in this way for about 56 million years. The complex of deposits (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); hence the name of the period. The deposits of that time are quite diverse: limestones, clastic rocks, shales, igneous rocks, clays, sands, conglomerates, formed in a variety of conditions.
Flora
In the Jurassic, vast territories were covered with lush vegetation, primarily with various forests. They mainly consisted of ferns and gymnosperms.
Cycads - a class of gymnosperms that prevailed in the green cover of the Earth. Now they are found in the tropics and subtropics. Dinosaurs roamed under the shade of these trees. Outwardly, cycads are so similar to low (up to 10-18 m) palm trees that even Carl Linnaeus placed them in his system of plants among palm trees.
In the Jurassic period, groves of gingko trees grew throughout the then temperate zone. Ginkgoes are deciduous (unusually for gymnosperms) trees with an oak-like crown and small, fan-shaped leaves. Only one species has survived to this day - ginkgo biloba.
Very diverse were conifers, 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 with the Triassic, the population of the seabed has changed a lot. Bivalves displace brachiopods from shallow waters. Brachiopod shells are replaced by oysters. Bivalve molluscs fill all the vital niches of the seabed. Many stop collecting food from the ground and move on to pumping water with the help of gills. A new type of reef communities is emerging, approximately the same as it exists now. It is based on six-ray corals that appeared in the Triassic.
Land animals of the Jurassic period
One of the fossil creatures that combine the features of birds and reptiles is Archeopteryx, or the first bird. For the first time, his skeleton was discovered in the so-called lithographic slates 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 flew quite badly (planned from tree to tree), and was about 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, they were preserved only in hoatzin chicks).
In the Jurassic period, small, woolly warm-blooded animals - mammals - live on Earth. They live next to dinosaurs and are almost invisible against their background. In the Jura there was a division of mammals into monotremes, marsupials and placentals.
Dinosaurs (English Dinosauria, from other Greek δεινός - terrible, terrible, dangerous and σαύρα - lizard, lizard) lived in forests, lakes, 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 move on two or four limbs. Among them were both predators and herbivores.
Scale
| Geological scale | |||
|---|---|---|---|
| Aeon | Era | Period | |
| F a n e R about h about th | Cenozoic | Quaternary | |
| Neogene | |||
| Paleogene | |||
| Mesozoic | Chalk | ||
| Yura | |||
| Triassic | |||
| Paleozoic | Permian | ||
| Carbon | |||
| Devonian | |||
| Silurus | |||
| Ordovician | |||
| Cambrian | |||
| D about to e m b R and th | P R about t e R about h about th | Neo- Proterozoic | Ediacaran |
| cryogeny | |||
| Tony | |||
| Meso- Proterozoic | Stenius | ||
| Ectasia | |||
| potassium | |||
| Paleo- Proterozoic | Statery | ||
| Orosirium | |||
| Riasius | |||
| siderius | |||
| BUT R X e th | neoarchean | ||
| Mesoarchean | |||
| paleoarchaean | |||
| Eoarchean | |||
| catarchean | |||
Jurassic subdivision
The Jurassic system is subdivided into 3 divisions and 11 tiers:
| system | the Department | tier | Age, million years ago | |
|---|---|---|---|---|
| Chalk | Lower | Berriasian | smaller | |
| Jurassic period | Upper (malm) | titonian | 145,0-152,1 | |
| Kimmeridge | 152,1-157,3 | |||
| Oxford | 157,3-163,5 | |||
| Medium (dogger) | Callovian | 163,5-166,1 | ||
| Bath | 166,1-168,3 | |||
| Bayosian | 168,3-170,3 | |||
| Aalen | 170,3-174,1 | |||
| Lower (lias) | Toarian | 174,1-182,7 | ||
| Plinsbachsky | 182,7-190,8 | |||
| Sinemursky | 190,8-199,3 | |||
| Goettansky | 199,3-201,3 | |||
| Triassic | Upper | Rhetic | more | |
| Subsections are given in accordance with IUGS as of January 2013 | ||||
Rostras of belemnites Acrofeuthis sp. Early Cretaceous, Hauterivian
Brachiopod shells Kabanoviella sp. Early Cretaceous, Hauterivian
Bivalve shell Inoceramus aucella Trautschold, Early Cretaceous, Hauterivian
Skeleton of a saltwater crocodile Stenosaurus, Steneosaurus boltensis Jaeger. Early Jurassic, Germany, Holzmaden. Among the saltwater crocodiles, the talattosuchian stenosaurus was the least specialized form. He developed not flippers, but ordinary five-fingered limbs, like in land animals, although somewhat shortened. In addition, a powerful bone shell made of plates has been preserved on the back and belly.
Three of the specimens displayed on the wall (crocodile stenosaurus and two ichthyosaurs - stenopterygium and eurhinosaurus) were found at one of the world's largest localities of the Early Jurassic marine fauna HOLTSMADEN (about 200 million years ago; Bavaria, Germany). For several centuries, the development of shale was carried out here, which was 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 fed on fish and insects. On some specimens of sordes, remnants of the hairline have been preserved, which is extremely rare in other localities.
Thecodonts- prenova group 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 position of their paws with a quadrupedal mode of locomotion (3,5,6), others - in parallel with the development of bipedality (2,7,8). Most thecodonts were terrestrial, but some of them were amphibious (6).
crocodiles close to thecodonts. Early crocodiles (1,2,9) were terrestrial animals, marine forms with flippers and a tail fin also existed in the Mesozoic (10), and modern crocodiles are adapted to an amphibious 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) have, to varying degrees, adopted an amphibious way of life. One of the most highly organized among the archosaurs were flying pangolins (26,27,28), which had wings with a flying membrane, hair, and, possibly, a constant body temperature.
Birds- are considered direct descendants of the Mesozoic archosaurs.
Small land crocodiles, united in the Notosuchia group, were widespread in Africa and South America during the Cretaceous period.
Part of the skull of a sea lizard - pliosaurus. 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, a short neck and long, powerful flipper-like limbs. Most of the pliosaurs had dagger-like teeth, and they were the most dangerous predators of the seas of the Jurassic period. This sample, 70 cm long, is only the front third of the pliosaurus skull, and the total length of the animal was 11-13 m. The pliosaurus lived 150-147 million years ago.
Larva of the Coptoclava beetle, Coptoclava longipoda Ping. This is one of the most dangerous predators in the lake.
Apparently, in the middle of the Cretaceous, the conditions in the lakes changed dramatically and many invertebrates had to go to rivers, streams, or temporary reservoirs (caddis flies, whose larvae build tube houses from grains of sand; Bottom sediments of these reservoirs are not preserved, flowing waters wash them away, destroying the remains of animals and plants. Organisms that migrated to such habitats disappear from the fossil record.
Houses of grains of sand, which were built and carried by caddisfly larvae, are very characteristic of the Early Cretaceous lakes. In later eras, such houses are found mainly in flowing waters.
Larvae of the caddisfly Terrindusia (reconstruction)
From: , 8625 views