What Animals Lived During The Eocene Epoch

2007 Schools Wikipedia Selection. Related subjects: Geology and geophysics

The Eocene epoch (56-34 Ma) is a major sectionalisation of the geologic timescale and the 2d epoch of the Palaeogene period in the Cenozoic era. The Eocene spans the fourth dimension from the terminate of the Paleocene epoch to the beginning of the Oligocene epoch. The starting time of the Eocene is marked past the emergence of the beginning modernistic mammals. The end is set at a major extinction event called Grande Coupure (the "Not bad Suspension" in continuity), which may exist related to the bear upon of 1 or more large bolides in Siberia and in what is now Chesapeake Bay. Equally with other geologic periods, the strata that define the beginning and end of the epoch are well identified, though their exact dates are slightly uncertain.

The name Eocene comes from the Greek eos (dawn) and ceno (new) and refers to the "dawn" of mod ('new') mammalian fauna that appeared during the epoch.

Paleogene catamenia
Paleocene epoch	Eocene epoch	Oligocene epoch
Danian | Selandian Thanetian	Ypresian | Lutetian Bartonian | Priabonian	Rupelian | Chattian

Eocene subdivisions

The Eocene is usually broken into lower and upper subdivisions. The Faunal stages from youngest to oldest are:

Priabonian	(37.2 ± 0.1 – 33.9 ± 0.one Ma)
Bartonian	(40.4 ± 0.ii – 37.2 ± 0.1 Ma)
Lutetian	(48.6 ± 0.2 – 40.4 ± 0.2 Ma)
Ypresian	(55.eight ± 0.2 – 48.6 ± 0.2 Ma)

Eocene climate

Marking the start of the Eocene, the planet heated upwardly in one of the about rapid (in geologic terms) and farthermost global warming events recorded in geologic history, called the Paleocene-Eocene Thermal Maximum or Initial Eocene Thermal Maximum (PETM or IETM). This was an episode of rapid and intense warming (up to 7°C at high latitudes) that lasted less than 100,000 years . The Thermal Maximum provoked a sharp extinction issue that distinguishes Eocene fauna from the ecosystems of the Paleocene.

The Eocene global climate was perhaps the almost homogeneous of the Cenozoic; the temperature gradient from equator to pole was only one-half that of today's, and deep ocean currents were exceptionally warm. The polar regions were much warmer than today, perhaps as mild equally the modern-day Pacific Northwest; that warm temperate forests extended right to the poles, while rainy tropical climates extended as far north as 45 degrees breadth away from the Equator. The deviation was greatest in the temperate latitudes; the climate in the torrid zone still, was probably similar to today'southward.(Stanley, 508)

Climates remained warm through the rest of the Eocene, although boring global cooling, which eventually led to the Pleistocene glaciations, started around the finish of the epoch as body of water currents around Antarctica cooled.

Eocene paleogeography

During the Eocene, the continents continued to drift toward their present positions.

At the beginning of the menstruum, Commonwealth of australia and Antarctica remained connected, and warm equatorial currents mixed with colder Antarctic waters, distributing the heat around the world and keeping global temperatures loftier. But when Australia split from the southern continent effectually 45 mya, the warm equatorial currents were deflected away from Antarctica, and an isolated cold water channel developed between the two continents. The Antarctic region cooled down, and the sea surrounding Antarctica began to freeze, sending common cold water and icefloes north, reinforcing the cooling.

The northern supercontinent of Laurasia began to break up, as Europe, Greenland and N America drifted apart.

In western North America, mountain building started in the Eocene, and huge lakes formed in the loftier flat basins among uplifts.

Europe saw the Tethys Body of water finally vanish, while the uplift of the Alps isolated its final remnant, the Mediterranean, and created some other shallow sea with isle archipelagos to the north. Though the North Atlantic was opening, a land connection appears to accept remained between North America and Europe, as the faunas of the two regions are very similar.

India continued its journeying abroad from Africa, and began its collision with Asia, folding the Himalayas into beingness.

• Detailed maps of Tertiary Western North America: Eocene
• Map of Eocene Earth

It is hypothesized that the Eocene hothouse earth was due to runaway global warming from released methane clathrates deep in the oceans. The clathrates were buried beneath mud that was disturbed as the oceans warmed. Methane (CH₄) has ten to twenty times the greenhouse gas effect of carbon dioxide (CO₂).

Eocene flora

At the beginning of the Eocene, the high temperatures and warm oceans created a moist, balmy surroundings, with forests spreading throughout the earth from pole to pole. Apart from the driest deserts, Earth must accept been entirely covered in forests.

Polar forests were quite all-encompassing. Fossils and even preserved remains of trees such every bit swamp cypress and dawn redwood from the Eocene have been institute in Ellesmere Island in the Canadian Arctic. Every bit aforementioned, the preserved remains found in the Canadian Arctic are not fossils, simply actual pieces preserved in oxygen-poor h2o in the swampy forests of the fourth dimension, so buried before they had the chance to decompose. Even at that time, Ellesmere Isle was only a few degrees in latitude farther southward than it is today. Fossils of subtropical and even tropical trees and plants from the Eocene take also been found in Greenland and Alaska. Tropical rainforests grew as far north equally the Pacific Northwest and Europe.

Palm trees were growing as far north equally Alaska and northern Europe during the early on Eocene, although they became less and less abundant as the climate cooled. Dawn redwoods were far more all-encompassing equally well.

Cooling began mid-menstruum, and past the end of the Eocene continental interiors had begun to dry out, with forests thinning out considerably in some areas. The newly-evolved grasses were still confined to river banks and lake edges, and had not yet expanded into plains and savannas.

The cooling also brought seasonal changes. Deciduous trees, better able to cope with big temperature changes, began to overtake evergreen tropical species. By the finish of the period, deciduous forests covered large parts of the northern continents, including North America, Eurasia and the Arctic, and rainforests held on only in equatorial South America, Africa, Bharat and Australia.

Antarctica, which began the Eocene fringed with a warm temperate to sub-tropical rainforest, became much colder equally the period progressed; the oestrus-loving tropical flora was wiped out, and by the start of the Oligocene the continent hosted deciduous forests and vast stretches of tundra.

Eocene fauna

Mesonyx, a carnivorous ungulate

The oldest known fossils of most of the mod mammal orders announced within a brief menstruation during the early Eocene. At the outset of the Eocene, several new mammal groups arrived in N America. These modern mammals, like artiodactyls, perissodactyls and primates, had features like long, sparse legs, feet and hands capable of grasping, equally well as differentiated teeth adapted for chewing. Dwarf forms reigned. All the members of the new mammal orders were small, under 10 kg; based on comparisons of tooth size, Eocene mammals were but 60 per cent of the size of the primitive Paleocene mammals that had preceded them. They were besides smaller than the mammals that followed them. It is assumed that the hot Eocene temperatures favored smaller animals that were better able to manage heat.

Both groups of mod ungulates (hoofed animals) became prevalent due to a major radiation between Europe and Due north America; forth with carnivourous ungulates similar Mesonyx. Early forms of many other modern mammalian orders appeared, including bats, proboscidians, primates, rodents and marsupials. Older primitive forms of mammals declined in variety and importance. Important Eocene country fauna fossil remains have been found in western North America, Europe, Patagonia, Egypt and South-Due east Asia. Marine fauna are best known from South asia and the southeast United States.

Reptile fossils are as well known from the Eocene, such as the fearsomely enormous crocodile Deinosuchus, which lived as far n as Wyoming during the Eocene and grew much larger than the modern-day saltwater crocodile. Python fossils and turtle fossils are also known from North America.

During the Eocene plants and marine faunas became quite modern. Many modernistic bird orders first appear in the Eocene.

Eocene oceans

The Eocene oceans were warm and teeming with fish and other sea life. The first Carcharinid sharks appeared, as did early marine mammals, including Basilosaurus, an early species of whale that is idea to be descended from land animals, the hoofed predators called mesonychids, of which Mesonyx was a fellow member. The first sirenians, relatives of the elephants, too appeared at this fourth dimension.

The Grande Coupure

The Grande Coupure, or "keen break" in continuity, with a major European turnover in mammalian animal well-nigh 33.v Ma, marks the end of the last phase of Eocene assemblages, the Priabonian, and the arrival in Europe of Asian immigrants. The Grande Coupure is characterized by widespread extinctions and allopatric speciation in small isolated relict populations. It was given its name in 1910 by the Swiss palaeontologist Hans Georg Stehlin, to characterise the dramatic turnover of European mammalian fauna, which he placed at the Eocene-Oligocene boundary. A comparable turnover in Asian fauna has since been called the "Mongolian Remodelling".

The Grande Coupure marks a break between endemic European faunas earlier the break and mixed faunas with a strong Asian component afterwards. J.J. Hooker and his squad summarized the break:

"Pre-Grande Coupure faunas are dominated by the perissodactyl family Palaeotheriidae (distant horse relatives), half-dozen families of artiodactyls (cloven-hoofed mammals) (Anoplotheriidae, Xiphodontidae, Choeropotamidae, Cebochoeridae, Dichobunidae and Amphimerycidae), the rodent family Pseudosciuridae, the primate families Omomyidae and Adapidae, and the archontan family unit Nyctitheriidae.

"Mail-Grande Coupure faunas include the true rhinos (family Rhinocerotidae), iii artiodactyl families (Entelodontidae, Anthracotheriidae and Gelocidae) related respectively to pigs, hippos and ruminants, the rodent families Eomyidae, Cricetidae (hamsters) and Castoridae (beavers), and the lipotyphlan family Erinaceidae ( hedgehogs). The speciose genus Palaeotherium plus Anoplotherium and the families Xiphodontidae and Amphimerycidae were observed to disappear completely.

"But the marsupial family unit Herpetotheriidae, the artiodactyl family Cainotheriidae, and the rodent families Theridomyidae and Gliridae ( dormice) crossed the faunal dissever undiminished." (Hooker et al. 2004)

Whether this abrupt change was caused by climate change associated with the earliest polar glaciations and a major fall in bounding main levels, or by competition with taxa dispersing from Asia, few would argue for an isolated unmarried cause. More spectacular causes are related to the touch on of one or more than large bolides in Siberia and in the Chesapeake Bay affect crater. Improved correlation of northwest European successions to global events (Hooker et al. 2004) confirms the Grande Coupure as occuring in the earliest Oligocene, with a hiatus of about 350 ka prior to the first record of post-Grande Coupure Asian immigrant taxa.

An chemical element of the paradigm of the Grande Coupure was the apparent extinction of all European primates at the Coupure: the contempo discovery of a mouse-sized early on Oligocene omomyid, reflecting the improve survival chances of small mammals, farther undercut the Grand Coupure prototype.

Source: https://www.cs.mcgill.ca/~rwest/wikispeedia/wpcd/wp/e/Eocene.htm

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