Life on earth during the Cretaceous. Cretaceous period. Key Features What Happened in the Cretaceous Period

The Cretaceous period is considered the longest period of the Mesozoic, as it lasted for about 79 million years.

Geography

The divided parts of the Pangea supercontinent drifted apart. The Tethys Ocean continued to separate the northern continent of Laurasia from southern Gondwana. The North and South Atlantic were still inaccessible. By the middle of the period, ocean levels were much higher; most of the land we knew was still under water. By the end of the period, the continents acquired outlines close to modern ones. Africa and South America have taken on their own distinctive forms; but India had not yet collided with Asia, and Australia remained part of the Antarctic.

Climate

During the Cretaceous period, climatic conditions on Earth became warmer. It was colder at the poles. Fossils of tropical plants and ferns support this assumption.

Animals lived everywhere, even in colder areas. For example, Late Cretaceous hadrosaur fossils have been found in Alaska.

When the asteroid struck, the world was likely experiencing a so-called "nuclear winter," when dust particles blocked many of the sun's rays from reaching the land surface.

Vegetable world

One of the hallmarks of the Cretaceous period was the development of flowering plants. The oldest fossil of angiosperms - Archaefructus liaoningensis- was found in China. This plant is believed to be most similar to modern black pepper and is at least 122 million years old.

It used to be that pollinating insects such as bees and wasps evolved around the same time as angiosperms, a process called coevolution (co-evolution). However, new research indicates that insect pollination was probably widespread even before the first flowers. While the oldest fossil bee is about 80 million years old, evidence has been found that bees or wasps built their nests in Arizona's Petrified Forest (Petrified Forest National Park).

Found by Stephen Hasiotis and his team at the University of Colorado, these nests are at least 207 million years old. It is now believed that competition for insect attention has likely contributed to the relatively rapid success and diversification of flowering plants. As a variety of flower forms lured insects for pollination, insects adapted to different ways of collecting nectar and moving pollen, thereby creating the complex co-evolutionary systems with which we are familiar today.

There is limited evidence that dinosaurs ate angiosperms. According to research published at the 2015 Society of Paleontologists Annual Meeting. In Utah, two dinosaur coprolites (fossilized excrement) were found that contained angiosperm particles. This conclusion, like others (including the fact that angiosperms are contained in the intestines of Early Cretaceous ankylosaurs), suggests that some animals ate flowering plants.

Animal world

During the Cretaceous period, more began to fly, joining the pterosaurs in the air. The origin of flights is debated by many experts. In the tree-down theory, it is believed that small reptiles may have evolved from hopping behavior. The ground-up hypothesis suggests that the small theropods may have jumped high to grab their prey and were able to develop the ability to fly. Feathers probably evolved from early skin, the main function of which, most likely, was thermoregulation.

If anything, it is clear that the birds were quite successful and became widely diversified during the Cretaceous period. Confuciusornis (125-120 million years ago) is a bird with a modern beak and huge claws at the fingertips. Iberomesornis was about the size of a sparrow, knew how to run, and probably ate insects.

By the end of the Jurassic, some large sauropods such as Apatosaurus and Diplodocus became extinct. But other giant sauropods, including the titanosaurs, flourished, especially in the late Cretaceous.

Large herds of herbivorous ornithischian dinosaurs also flourished during the Cretaceous, including the iguanodont, ankylosaurus, and horned dinosaurs. Theropods including Tyrannosaurus rex, continued to remain at the summit until the end of the Cretaceous.

Mass Cretaceous-Paleogene (K-T) extinction

About 66 million years ago, almost all large and many tropical became extinct. Geologists call this a Cretaceous-Paleogene extinction event because it marks the boundary between the Cretaceous and Paleogene.

In 1979, a geologist studying rock layers between the Cretaceous and Paleogene discovered a thin layer of gray clay separating the two eras. Other scientists have found this gray layer all over the world, and tests have shown that it contains high concentrations of iridium, which is rare on Earth but is common in most meteorites.

Also present in this layer are signs of "shocked quartz" and tiny glass particles called tektites, which are formed by the rapid heating and rapid cooling of rock, as occurs when an extraterrestrial object hits the Earth with great force.

Chicxulub crater on the Yucatan Peninsula dates back to this time. The crater is more than 180 kilometers in diameter, and chemical analysis shows that the sedimentary rocks of the area were melted and mixed together depending on the impact of the impact of an asteroid about 10 kilometers in diameter.

When the asteroid hit the Earth, it caused shock waves, massive tsunamis, and sent a large cloud of hot rocks and dust into the atmosphere. As the hot debris fell to Earth, it sparked numerous forest fires, raising the ambient temperature.

A rain of dust and rocks raised the global temperature on the planet within hours of the impact and wiped out animals that were too large to seek refuge. Small representatives of the fauna, hiding under the ground or water, in caves or large tree trunks, were probably able to survive this disaster.

The tiny fragments most likely remained in the atmosphere and blocked some of the sun's rays for months or years. With a decrease in the amount of sunlight, plants could not participate in and died, like the animals that fed on them.

Smaller, terrestrial animals such as mammals, lizards, turtles, and birds may have been able to survive as scavengers by feeding on the carcasses of dead dinosaurs, fungi, roots, and decaying plant matter.

There is also evidence that a series of huge volcanic eruptions occurred along the tectonic boundary between India and Asia, and began just before the Cretaceous-Paleogene extinction. It is likely that these regional catastrophes affected many living organisms on the planet.

Cretaceous period - geological period, the last period of the Mesozoic era.

It began 145 million years ago and ended 65 million years ago. The Cretaceous period lasted for about 80 million years.

In the Cretaceous period, the first angiosperms appeared - flowering plants. This led to an increase in the diversity of insects that became flower pollinators. The evolution of the plant world gave impetus to the rapid development of the animal world, including dinosaurs. The diversity of dinosaur species reached its peak during the Cretaceous.

Cretaceous tectonics

During the Cretaceous period, the movement of the continents continued. Laurasia and Gondwana were falling apart. Africa, India and Australia also began to diverge in different directions, and as a result, giant islands were formed south of the equator. South America and Africa moved away from each other, and the Atlantic Ocean became wider and wider. There were no obvious catastrophes in the Cretaceous period, so the process of evolution proceeded naturally. The land took shape very close to those that are known to us.

Cretaceous climate

The climate has changed in comparison with the Jurassic period. Due to the change in the position of the continents, the change of seasons became more and more noticeable. Snow began to fall at the poles, although there were no such ice caps as now on Earth. The climate was different on different continents. This caused differences in the development of flora and fauna in different parts of the world.

Flora of the Cretaceous period

The flora of the Cretaceous period was rich and varied. In addition to the plant species that have passed from the Jurassic period, a new, revolutionary branch of flowering plants appears

Gradually settling on land, new groups of plants began to form vast forests. There, a wide variety of leaves and other edible vegetation were at the service of land animals. Due to the appearance of flowering plants in the Cretaceous, the amount of plant biomass increased.

The reverse process took place at sea. This was again aided by the development of flowering plants. The dense roots prevented soil erosion and therefore fewer minerals were allowed to enter the sea. The amount of phytoplankton has decreased.

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Cretaceous period is the last of the three periods that make up the Mesozoic era. It began 144 million years ago, lasted almost 80 million years and ended 65 million years ago. Its name comes from the abundance of writing chalk formed from dying invertebrates in its sediments. The Cretaceous period is remarkable for the second largest (after the Permian) world extinction of species.

Cretaceous division, geographic features and climatic changes

In 2016, the International Union of Geological Sciences adopted the following Cretaceous subdivision:

The lower section is divided into the Berriassian, Valanginian, Hauterivsky, Barremian, Altsky and Albian stages;
The upper section is subdivided into the Cenomanian, Turonian, Cognac, Santonian, Campanian and Maastricht tiers.

Cretaceous (chalk)	Departments	Tiers
	Lower	Berriasian
		Valanginian
		Hoterivsky
		Barrem
		Altsky
		Albian
	Upper	Cenomanian
		Turonian
		Cognac
		Santonese
		Campanian
		Maastricht

In the Cretaceous, the division of Laurasia into the North American continent and the European-Asian continent continued. Gondwana finally disintegrated into the South American continent, the African, Indian segment, Antarctica and Australia. Throughout the Cretaceous, these gigantic land areas diverged more and more from each other, the southern and northern parts of the Atlantic Ocean were now connected not by narrow straits, but acquired an integral oceanic structure. But, despite this, a significant part of Europe, the Middle East, the Caucasus and the northern part of Africa were still under water until the very end of the Cretaceous.

Cretaceous climate compared to the previous Jurassic, it became noticeably colder. At first, its average temperature across the planet dropped by 5 degrees, which led to the formation of pole ice caps, but after a while the climate warmed up again, and in general it was relatively warm throughout the planet, winter temperatures even in the coldest zones of the globe fluctuated on average within + 4 ° C. Towards the end of the period, the greenhouse effect caused by spillovers caused an even larger and sharp rise in temperature.

Sedimentation

The Cretaceous period is characterized by the highest flysch accumulations in the entire history of the Earth in geosyncal areas. As a result of violent magmatism caused by the splitting of continental regions, siliceous and split-dibasic formations were formed, and granitoid ejections are extensive and grandiose. In general, the accumulation of trigene and volcanogenic strata was widespread during the Cretaceous. Such rift zones arose in Africa and Brazil. In the depths of the sea, huge strata of writing chalk accumulate.

Cretaceous animals

The most significant among marine invertebrates in the Cretaceous period were cephalopods. In the Upper Cretaceous, the role of outer shell (ammonoids) slightly decreased, but intra shell (belemnites) were fundamental until the very end of the period. Closer to the middle, some ammonoids, for example, such as ammotoceras, reached 2 meters in size.

Such mollusks as pelecypods (bivalves) and gastropods (gastropods) were also widely developed. Most bivalves will be completely extinct by the end of the Cretaceous. Irregular sea urchins also developed along with large foraminifers.

Felt great and Cretaceous insects... Most of them, adapted to today's flowering plants, were forced to change themselves due to biological changes in vegetation, but in general, the species of both flying and crawling insects progressed steadily. All kinds of worms also felt great.

The first lobsters and other predatory crustaceans such as crabs and shrimps appeared in coastal seas and oceanic zones.

Rice. 1 - Dinosaurs of the Cretaceous period

Vertebrates Cretaceous animals were distinguished by the fact that among them, as in the Jurassic period, reptiles reigned supreme (Fig. 1). Among them were crawling, and walking on four limbs, and moving only on two hind limbs, and waterfowl and, of course, flying hymenoptera. The richness of their varieties and forms was truly amazing. This entire large army of reptiles incessantly devoured both huge masses of green spaces and themselves, meanwhile, increasing in numbers, until incomprehensibly in the upper Maastrichtian tier of the Cretaceous period almost completely and everywhere died out.

The first snakes appeared (Fig. 2). Some grew to truly gigantic sizes and hunted mainly in the aquatic environment, in coastal or river basins. For some of them it was not difficult to twine around and crush or strangle the gaping one and a half meter raptor.

Rice. 2 - Cretaceous snake

The variety of flying dinosaurs was also great. The real giant was the pteradon, whose wingspan averaged 8 meters. These giant reptiles hunted mainly over the sea, diving with ease in the air currents and now and then, snatching fish and other representatives of the marine fauna from the water.

Birds also developed widely, the first species of which appeared in the Jurassic period. In the Cretaceous period, highly organized and specialized formations appeared among them.

And in the depths of the sea, fish with a hard-boned skeleton were further developed. The ray-finned offspring of the Triassic and Jurassic multiplied unusually, a huge number of new species appeared, both among the inhabitants of freshwater and inland basins, and among salty marine and oceanic species (Fig. 3).

Rice. 3 - Cretaceous marine animals

Despite the undivided domination of reptiles, mammals still advanced in their evolutionary development in the Cretaceous period. Having appeared on the threshold of the Mesozoic, these animal-like animals (synapsids) slowly but surely waited for their time throughout the era, more and more adapting to the difficult life in the background. Synapsids often settled in cold areas of the continents, where predatory, but thermophilic reptiles were rare guests. Those who were forced to live among reptiles in hot regions went out to hunt mainly at night. All this greatly contributed to their habituation to difficult conditions, which caused mammals to survive in the difficult conditions of the asteroid winter that hit the Earth at the end of the Cretaceous.

Everything synapsids were divided into three main types - dicinodonts, cynodonts and alloteria. Dicyodonts and cynodonts became almost completely extinct during the Cretaceous period, and allodonts developed into mammals. During the Late Jurassic and subsequent Cretaceous period, they clearly divided into three branches - oviparous, marsupial and placental. Oviparous, unable to withstand competition with marsupials and placentals, soon also disappeared, marsupials today survived only on the territory of Australia, namely from placentals and all subsequent species of modern mammals developed. The placentals at that time were divided into larasiatheria and gondvanateria. It was the Gondvanotheria that were the ancestors of modern rodents and primates.

From the marsupial branch opossum-like ones originated, and from the oviparous at the present time only one platypus has remained. The ancestor of primates is considered to be the ancient mammal Purgatorius.

Primarily Cretaceous mammals(Fig. 4) weighed no more than half a kilogram and rarely exceeded the size of a modern rat. There were, of course, such rare specimens as one-meter and fourteen-kilogram repenomas, but they were too few in number.

Rice. 4 - Cretaceous mammals

For the most part, reptiles owe their extinction to these small creatures, which, having multiplied unusually by the end of the Cretaceous, fed mainly on insects, but did not disdain the eggs of reptiles.

Despite the fact that the first flowering plants began to appear long before the Cretaceous period, it was at this time that the formation of flowering plants entered the stage of a real boom. It is no coincidence that half of all currently known plants are flowering. And this is connected with this.

By spreading spores downwind, primitive plants took great risks. And not in vain, since the bulk of the disputes never reached their intended goal. And many plants of that era have not yet acquired at least some varieties of spore dispersion mechanisms. Their spores were forced to fall to the ground, right in the same place where the plants themselves grew. It is clear that with such a reproduction it was not possible to achieve a more or less reliable result. Hence the vital need for the development of new, more effective methods for the distribution of pollen. And insects came to the aid of the plants.

A kind of union began to improve and grow stronger between the flower groups. While the insects carried the pollen of the plants, the plants produced nectar for them to work more intensively on pollination. In the process of evolution, it so happened that many insects simply could no longer do without flowering plants, since their whole life and body biology was inextricably linked and aimed at life associated with such plants. And the plants, with the help of their insect assistants, began to multiply many times faster, and soon dense vegetation spread even to those parts of the land on which it had never existed before. This kind of partnership between plants and insects persists even sow the day.

Rice. 5 - Plants of the Cretaceous period

Underwater Cretaceous plants were in many ways similar to plants of the previous periods of the Mesozoic. The only difference was that microscopic algae such as nanoplankton (for example, golden coccolithophorids) and diatoms multiplied unusually. It is nanoplankton and small foraminifera that are responsible for the formation of such thick layers of writing chalk.

By the end of the Mesozoic era, the flora of the land has undergone a number of significant changes. From the middle of the Cretaceous period, the first angiosperms began to appear, which, towards the end of the Cretaceous, already constituted the overwhelming majority of terrestrial plants. The first varieties of plants with foliage of increased juiciness began to appear. This applies most to places where the climate began to acquire a more arid and hot character.

What happened at the turn of the Mesozoic and Cenozoic, or rather, in the Maastrichtian - the final stage of the upper section, Cretaceous extinction of species was the second largest after the Permian. Overnight, the coccolithophorids ceased to exist, and the Cretaceous planktonic foramonifera, ammonites, belemnites, coral-like bivalve mollusks - rudists - disappeared. Dinosaurs and many other species of reptiles have disappeared from the face of the earth. Many species of birds and insects of both the surface and the underwater world have ceased to exist. In particular, the total number of all kinds of raliolaria decreased by 50%, 75% of all brachiopods, from 30 to 75% of bivalves and gastropods, sea lilies and hedgehogs became extinct. Only 25% of the total number of sharks remained. More than 100 different families of marine invertebrates have ceased to exist. In general, the damage suffered by the flora and fauna was truly enormous.

What caused such a massive extinction of species in the Cretaceous still not known. Scientists are divided on this issue. Opinions were also expressed about the fact that the powerful cosmic radiation formed as a result of a supernova explosion reached the Earth. Someone speaks of a strong greenhouse effect associated with extremely aggravated volcanic activity. But most stand for the version based on falling to the ground. giant asteroid(fig. 6). This version is confirmed by the presence of inclusions of iridium in the strata of this era, which is constantly found in places where meteorites fall.

Rice. 6 - The fall of the asteroid

It is argued that an asteroid from 10 to 15 km in size, entering the earth's atmosphere at great speed, split into several segments, which collided with the earth's surface. The explosive energy, amounting to about 10 to the 30th power of erg, lifted a lot of pollutant from the earth's crust, which for a long time blocked access to sunlight for plants and animals. Thus, as a result of a kind of "asteroid winter", the majority of land animals died out. Apparently, this did not affect the plant world so much because the atmosphere cleared up in a relatively short period of time. And if the seeds of plants successfully survived this disaster in the soil and soon simply sprouted as if nothing had happened, then the fauna of the Cretaceous period could not withstand this global catastrophe with such ease. And as a result, only the fittest and more tenacious species survived, such as, for example, mammals.

Cretaceous minerals

The Cretaceous period is unusually fertile for various types of minerals, most of which arose as a result of intrusive magmatism and volcanism, which accompanied the worldwide division of Pangea into smaller components. About 20% of coal deposits have been accumulated during this time. The largest coal basins of this period are Lensky and Zyryansky, as well as a number of North American coal basins.

Most of the Russian, French and Spanish deposits of bauxite, West Siberian oil and gas deposits, oil and gas deposits of Kuwait and Canada are also associated with the Cretaceous period. On the territory of Western Siberia, vast deposits of oolitic iron ores were discovered. There are also numerous phosphate deposits in the territories of Russia, Morocco, and Syria. On the territory of Turkmenistan and in some North American regions, extensive salt deposits have been found. Deposits of tin, lead and gold have been discovered in the north-east of Russia, in North America. The famous Indian and South African diamond deposits also belong to this period.

Writing chalk has been found almost everywhere in Cretaceous sediments.

Which is extracted from sedimentary deposits of this period, formed by rich accumulations of fossil invertebrates of marine organisms.

Cretaceous divisions

system	the Department	tier	Age, million years ago
Paleogene	Paleocene	Danish	less
chalk	Upper	Maastricht	72,1-66,0
		Campanian	83,6-72,1
		Santonese	86,3-83,6
		Cognac	89,8-86,3
		Turonian	93,9-89,8
		Cenomanian	100,5-93,9
	Lower	Albian	113,0-100,5
		Aptsky	125,0-113,0
		Barrem	129,4-125,0
		Hoterivsky	132,9-129,4
		Valanginian	139,8-132,9
		Berriasian	145,0-139,8
Yura	Upper	Titonian	more
Division given in accordance with IUGS as of December 2016

The Aptian anoxic event (Selli Event or OAE 1a) took place about 120 million years ago. About 116 million years ago, the average temperature on the planet dropped by 5 ° C, the global cooling lasted more than a million years. Then the warming began again - the volcanoes of the Indian Ocean began to pump carbon into the atmosphere. Global warming led to the depletion of oxygen in ocean waters, which, 94 million years ago, led to an "anoxide catastrophe" and the extinction of ichthyosaurs that did not adapt to climate change.

Approximately 91.5 ± 8.6 million years ago, a Cenomanian-Turonian biotic event took place, which led to the complete disappearance of ichthyosaurs and pliosaurs, megalosaurian and stegosaurian families, and greatly reduced the species diversity of other groups of animals.

70 million years ago, the Earth was cooling. Ice caps have formed at the poles. The winters were getting harsher. The temperature dropped in places below -10 degrees, and in Alaska - down to -45. For the dinosaurs of the Cretaceous period, this difference was sharp and very noticeable, more cold-loving species became more widespread. Such temperature fluctuations were caused by the split of Pangea, and then Gondwana and Laurasia. The sea level rose and fell. The jet streams in the atmosphere have changed, as a result of which the currents in the ocean have changed.

Vegetation

In the Cretaceous period, angiosperms appeared - flowering plants. This led to an increase in the diversity of insects that became flower pollinators. As temperatures increased at the end of the Cretaceous period, plants with more succulent foliage developed.

Animal world

A variety of large reptiles reigned among land animals. This was the heyday of giant dinosaurs - many dinosaurs reached 5-8 meters in height and 20 meters in length. Winged reptiles - pterodactyls - occupied almost all niches of aerial predators, although real birds have already appeared. Thus, flying lizards, lizard-tailed birds such as Archeopteryx and true fan-tailed birds existed in parallel.

At the end of the period, serpents spread.

There were no mammals in the seas, and the niche of large predators was occupied by reptiles with a comparable level of metabolism - ichthyosaurs, plesiosaurs, mosasaurs, sometimes reaching 20 meters in length.

The diversity of marine invertebrates was very great. As in the Jurassic period, ammonites and belemnites, brachiopods, bivalves and sea urchins were very common. Among bivalve molluscs, a large role in marine ecosystems was played by the rudists that appeared at the end of the Jurassic - mollusks that looked like solitary corals, in which one valve looked like a goblet, and the other covered it like a kind of lid.

By the end of the Cretaceous period, a lot of heteromorphic ones appeared among the ammonites. Heteromorphs appeared earlier, in the Triassic, but the end of the Cretaceous became the time of their mass appearance. The shells of the heteromorphs did not resemble the classical spiral-twisted shells of monomorphic ammonites. It could be spirals with a hook at the end, various tangles, knots, unrolled spirals. Paleontologists have not yet come to a common explanation of the reasons for the emergence of such forms and their way of life.

Orthocerases were still found in the seas - relics of a long past Paleozoic era. Small shells of these rectal cephalopods are found in the Caucasus.

Cretaceous disaster

At the end of the Cretaceous, the most famous and very large extinction of many groups of plants and animals occurred. Many gymnosperms, aquatic reptiles, pterosaurs, all dinosaurs died out (but birds survived). Ammonites, many brachiopods, practically all belemnites have disappeared. In the surviving groups, 30-50% of the species became extinct. The reasons for the Cretaceous catastrophe are not fully understood.

Notes (edit)

International Chronostratigraphic Chart v. 2019-05 (unspecified) ... International Commission on Stratigraphy (2019). Archived August 13, 2019.
N. M. Chumakov. The climate in the era of major biospheric restructuring. M: Nauka, 2004 .-- 299 p. Ch. 5. Climatic zonation and climate of the Cretaceous period.
Li, Yong-Xiang; Bralower, Timothy J .; Montañez, Isabel P .; Osleger, David A .; Arthur, Michael A .; Bice, David M .; Herbert, Timothy D .; Erba, Elisabetta; Premoli Silva, Isabella. Toward an orbital chronology for the early Aptian Oceanic Anoxic Event (OAE1a, ~ 120 Ma) // Earth and Planetary Science Letters (English) Russian: journal. - 2008 .-- July 15 (vol. 271, no. 1-4). - P. 88-100. - DOI: 10.1016 / j.epsl.2008.03.055.
Mid-Cretaceous "global cooling" explored, June 18th, 2013
Extinction of ichthyosaurs explained by the slowness of their evolution, March 11, 2016
Head J. J. Fossil calibration dates for molecular phylogenetic analysis of snakes 1: Serpentes, Alethinophidia, Boidae, Pythonidae (English) // Palaeontologia Electronica (English) Russian: journal. - 2015.
Caldwell M. W., Nydam R. L., Palci A., Apesteguía S.

Cretaceous tectonics:

During Cretaceous the movement of the continents continued. Laurasia and Gondwana were falling apart. Africa, India and Australia also began to diverge in different directions, and as a result, giant islands were formed south of the equator. South America and Africa moved away from each other, and the Atlantic Ocean became wider and wider. Some obvious catastrophes in Cretaceous period was not, so the process of evolution was natural. The land took shape very close to those that are known to us.

Climate Cretaceous:

Flora Cretaceous:

Flora Cretaceous was rich and varied. In addition to the plant species that have passed from the Jurassic period, a new, revolutionary branch of flowering plants appears. Flowering plants, having entered into an "alliance" with insects, had advantages over their predecessors. Through this partnership, flowering plants spread much faster. Gradually settling on land, new groups of plants began to form vast forests. There, a wide variety of leaves and other edible vegetation were at the service of land animals. Due to the emergence of flowering plants in Cretaceous period the amount of plant biomass has increased.
The reverse process took place at sea. This was again aided by the development of flowering plants. The dense roots prevented soil erosion and therefore fewer minerals were allowed to enter the sea. The amount of phytoplankton has decreased.

Fauna Cretaceous:

Insects:

Flowering plant growth Cretaceous contributed to the increase in species of insects that feed on nectar and carry pollen. Exactly at Cretaceous period. Insects have appeared, the life of which is completely dependent on flowering plants. These are bees and butterflies. Insects collected pollen and delivered it to their destination. The brightly colored petals and the attractive scent of flowers are the bait for the insects. In turn, the sweet sugary nectar, and the pollen itself, supplied insects with all the nutrients they needed. Cretaceous period was the beginning of an era of close interaction between plants and insects.

Dinosaurs:

A variety of dinosaurs reigned among land animals. In the Cretaceous the variety of dinosaur species was especially great. The development of the plant kingdom and the increase in plant biomass gave impetus to the emergence of new species of herbivorous dinosaurs.
Of the lizard-like dinosaurs, the most famous of which was tyrannosaur were distributed tarbosaurus, spinosaurus, deinonychus other.
The variety of ornithischian dinosaurs is especially great during the Cretaceous period. Widely known in Jurassic period, stegosaurus will disappear from the face of the planet. Their place will be taken by such famous herbivorous dinosaurs as iguanodons, triceratops, ankylosaurus, pachycephalosaurus and many other types.

First mammals:

The first animal-like animals appeared in the Triassic period, about 220 million years ago. These animals belong to the so-called group of synapsids.
In the first half Cretaceous, in the environment of these imperceptible, against the background of dinosaurs, mammals, serious evolutionary processes began to take place. As a result, these processes resulted in the emergence of monotremes and placental mammals. It is to these groups of animals at the end Cretaceous and the beginning of the Cenozoic era was destined to become the successors of the dinosaurs.

The vast majority of Cretaceous synapsids are mammals. Primitive dicynodonts and cynodonts have not yet died out, but they are already close to that. Almost all mammals Cretaceous belonged to the primitive subclass of allotheries and differed little from the Jurassic predecessors. They were small creatures weighing 20-500 g, similar to mice. Among them there were also repenomamas reaching a length of 1 m and weighing up to 14 kg, but most were as small as other mammals of the Cretaceous period.

Initially Cretaceous from the alloteria, the true animals separated - the ancestors of modern mammals. They quite quickly divided into three main branches: oviparous, marsupial and placental mammals, and the placentals have already divided into laurasiatheria, gondvanateria, and the latter divided into rodents and primates. The marsupial branch gave birth to almost modern possums, and the oviparous branch gave birth to almost modern platypuses. The first known primate-like mammal was the purgatorius.

Flying:

Winged reptiles - pterodactyls occupied almost all niches of aerial predators. Cretaceous period spawned the largest flying creatures that have ever lived on Earth. These are giant orcheopteryx and quetzatcoatl. To date, the question of which of them was the largest has not been finally resolved.

But in the Cretaceous period, pterosaurs appeared competitors - birds. And although the first birds appeared in the Jurassic period, in Cretaceous period, the variety of their species has increased. A transitional species between pterosaurs and birds - the archiopteryx became extinct. Thus, flying lizards and birds existed in parallel.
Some Cretaceous birds are the ancestors of modern birds. Already in Cretaceous period ducks, semi-footed geese, loons and plovers appeared, almost indistinguishable from modern versions of these birds. Many of the birds Cretaceous were a dead-end branch of evolution and later became extinct. Bird classification Cretaceous very vague and contradictory.
The sizes of the Cretaceous birds varied from 4 cm to 1.5 m in length, and the weight - from a few grams to several kilograms.

Marine fauna:

There were no mammals in the seas, and the niche of large predators was occupied by reptiles - ichthyosaurs, plesiosaurs, mososaurs, sometimes reaching 20 meters in length.
Most of the inhabitants of the Cretaceous seas were plesiosaurs with long necks and small heads, feeding on small fish and molluscs. They could not swim fast, but they were very maneuverable, and their small head on a very long neck made it difficult for them to spot a school of prey in time - the fish saw only a small head, and a huge body was lost in the distance. A striking representative of this species was the Elasmosaurus up to 20 m long and weighing 14 tons.

Another species that lived in the seas Cretaceous there were mosasaurs. Mosasaurs are very large carnivorous, sea lizards that reigned in the Cretaceous seas. They replaced the Jurassic saltwater crocodiles. They were very aggressive animals - many Mosasaurs have traces of healed fractures and bites on their bones, obviously obtained in fights with their own kind.

Turtles Cretaceous practically did not differ from modern ones. The sizes of the Cretaceous turtles varied from 20 cm to 4.6 m, the weight reached 2 tons. Most of the species were aquatic.

Other reptiles:

V Cretaceous period the first lizards and snakes arose, so the snakes. They have survived to this day practically unchanged. This is a relatively young group of animals.

All Cretaceous dinosaurs

Herbivorous dinosaurs:

Sauropods: abidosaurus ... agustinia ... alamosaurus ... amargosaurus ...

ampelosaurus ... aragosaurus ... Argentinosaurus ... egyptosaurus ... laplatasaurus ...

maxcalizaur ... nigersaurus ... paralytitan ... Saltasaurus ... seismosaurus ...

Thierophores, ankylosaurids: acantofolis ... alopelta ... ankylosaurus ...

minmi ... nodosaurus ... scolosaurus ... styracosaurus ... thalarurus ... evoplacephalus

Ceropods: avaceratops ... agatamus ... adasaurus ... adamantisaurus ...

ankyceratops ... barillium... hypselospin ... gipselophodon ... zalmoxis ...

iguanodon ... zuniceratops ... coahuylaceratops ... leptoceratops ...

jellyfish ... monoclone ... muttaburrasaurus ... ochoceratops ...

pachyrinosaurus ... protoceratops ... psitaccosaurus ...stegoceras ... torosaurus ...

treceratops ... chazmosaurus ...

Hadrosaurs: anatotitan (anatosaurus)... brachylophosaurus ... hadrosaurus ...

saurolophus ... corytosaurus ... lambeosaurus ... mayasaur ... parasaurolophus ...

probactosaurus ... tenodontosaurus ... uranosaurus ... edmontosaurus ...

Pachycephalosaurus: Dracorex ... pachycephalosaurus ... stegoceras ... techcephalus

Carnivorous dinosaurs:

Theropods: abelisaurus ... avimim ... australovenator ...