The Tertiary Period. Oligocene epoch

The oligocene epoch on the Earth proceeded 16 million years. The Oligocene beginning is remote from our time approximately on 35 million years. In Oligocene there was no any more a bond through Atlantic ocean between Europe and the North America. America has still been bridged to Greenland, and through Bering strait and with Asia which extended the north much further, than now. Africa rose absolutely separate mainland, on its modern (western and east) shores were under water, as well as Madagascar. Europe represented the big island which compound included Scandinavia and northern half of the Western Europe. The Great Britain has formed the second island. All other part of Europe has been filled in by a Tethys which intercommunicated through Persia with Indian ocean, and through Western - the Siberian lowland - with Northern polar sea. The South America the season most part preserved the isolated position, but for short time it was bridged to the North America. In the end of Oligocene and result of grandiose orogenic processes the Himalayas have risen. The climate of Oligocene moderated and wet, in comparison with a climate of Eocene was a little more cool and dry. Palm trees grew on northern mainlands not so abundantly, but on former here evergreen forests still overtopped. Among them became more needle-leaved and the deciduous trees periodically dumping leafage.

The main vicissitudes in life of the oligocene seas consisted in reduction of nummuliteses which epoch by the end have died out, and in increase of number of bony fishes.

On a land it became considerable - more than entomophagous mammals. There were shrews, moles. In air together with customary entomophagous bats larger bats eating fruits rushed. In forests fundamental the squirrel figurative gnawers still came across, but together with them there lived also the present squirrels, ancestors of mice, jackrabbits, related to jackrabbits of creepers, and also ancestors of porcupines. These gnawers, having got to the South America, here became more various and is more numerous, than on other continents. The died out ancient edentateses now in the South America have changed new edentateses battleships and their close relatives glyptodonts. The testa of battleships consisted of separate rings, was mobile bridged among themselves, and at glyptodonts it was integral, as at turtles. In forests the first came across, still small terraneous idlers. On northern mainlands small ancient predators - creodontas - lived last days. Them have beaten in (vital contest the present predators - ancestors of dogs, martens, civet and cats. Except them, there lived predators - a bear of a dog. A bear - dogs with Oligocene were insignificant. Their dimension fluctuated between the dimensions of a fox and a wolf. They had a long tailing as at dogs, and they as a dog, - leaning to pour on dactyls of feet went, instead of on all autopodium as bears. But dens at these animals gradually became more and more stupid as at bears, and served them for grinding of vegetative nutriment. Oligocene cats are already divided on two bunches. At one both the upper and inferior canines are educed more or less equally as at our cats, at others - saber-toothed cats - terrible upper canines on the dimension considerably surpassed the inferior. Minings at predators was much. In oligocene forests still there lived the present tapirs and together with them tridactyl ancestors of horses - Mesohippus. Eating soft, juicy feedstuff. Last steels more largly also have reached the dimensions of a sheep-dog, and relocated to Europe anchithere on growth there was any more less nag. In the North America the titanothereses which have reached of the huge dimensions especially educed. The majority of them had pair horns. The length megacerops is equal almost 5 m and height of 2,5 m. Weak development of a brain and imperfection of dens have served as the cause to that titanothereses by the Oligocene end have given way to other hoofed animals. Cursorial and water rhinoceroses have died out, not having held out a competition to ancestors of horses. In Oligocene there lived many acerous rhinoceroses, related the modern. Among them were fine epiracerateria. Magnitude from the calf, and giants among all mammals - Indricothere. One head Indricothere at length is more 1,25 m, and height in shoulders nearby 5, 5 m.

Artiodactyl ruminant (ancestors of our deer, antelopes, a giraffe, goats, and bulls) reminded sheep of modern chevrotains or a musk deer. They are small acerous animals with strongly educed canines in the upper jow, with four dactyls on forward feet and two on back.

In Oligocene especially was pigs and animals close to them much. On shores of the rivers and lakes and canes short-legged Anthracoteridaes hid. On all northern mainlands huge pigs - Entelodon wandered. Their length reached to 3,25 m. At some Entelodon standing was only on two dactyls, and at others, except two big dactyls, was also on two small lateral. These animals reminding long-legged river horses, ate mainly roots of plants.

On former only in the North America there lived ancestors of camels - poebrotherium. Now they became growth about a sheep, but standing still preserved simple hoofs and had no non-crushing pillows, characteristic for modern camels.

The South American hoofed animals in Oligocene were very numerous. Here there were fine animals, like gnawers, and large heavy tridactyl Toxodon Astrapotherium reached the dimensions of the Rhinoceros. One hoofed animals from bunch litoptern - reminded harmonous tridactyl horses, and others were ancestors pleistocene Macrauchenia. Changing absent in the South America proboscidean, wandered large Pyrotherium. At them the present trunk educed, and chisels formed short tusks.

The African continent on the former was populated by the presents proboscidean. Ancient mastodonts, ancestors of taxodont mastodonts were especially numerous. With them together there lived Phiomias. The inferior jow of a Phiomia was already extended, but tusks and a trunk remained still short. Dens at a Phiomia bumpy. Phiomias - ancestors of bunodont mastodonts. Together with ancestors of elephants there lived ancestors of the presents a dog of figurative monkeys - Parapithecus and even the first subhuman primates - propliopithecine. From the inferior Oligocene of Africa are known original Arsinoitherium - far relatives of elephants and sirens, five-fingered animals for growth from a rhinoceros. On a head they had two pairs horns.

Oligocene sirens, or sea cows, on the constitution reminded modern sirens. Ancient whales have died out in Oligocene; by the season end in the sea toothed whales - Squalodon and ancestors of edentate whales floated already shortly a body. One of them (cetotherium) were absolutely edentate, and others (patricetus) still have completely preserved dens.