The Grande Coupure Era: How It Changed Everything

An example of the Grande Coupure was the extinction of all European primates at the Coupure: the recent discovery (Kohler and Moya-Sola 1999) of a mouse-sized early Oligocene omomyid, reflecting the better survival chances of small mammals, also helped with the Grand Coupure example.

Whether this abrupt change was caused by the climate change that came with the earliest polar glaciations and the major fall in sea levels, or by competition with species dispersing from Asia, few could argue for an isolated single cause. More causes are related to the effect of one or more large bolides in present day Siberia and Chesapeake Bay. Which Improved correlation of northwest European successions. this confirms the Grande Coupure as occurring in the earliest Oligocene, with a gap of about 350 thousand years before the first record of post-Grande Coupure Asian immigrant taxa.

They noted that the only families to cross the faunal divide undiminished were the marsupial family Herpetotheriidae, the rodent families Theridiidae, Dormouse and the artiodactyl family Cantharidae.

The Grande Coupure, which was a major European turnover in mammalian fauna about 33.5 Mya, marks the end of the last phase of Eocene gathering , the Priabonian, and the arrival of Asian species

The oceans were warm and filled with fish and other sea life. The first Carcharhinid sharks appeared, just like land mammals live continued to growing many more animals formed including Brachiosaurus, which was an early species of whale that is thought to have descended from land animals, the hoofed predators called nemonychidae. The first sirenians (a large plant – eating mammal), relatives of the elephants.

During the Eocene plant and marine faunas became quite modern.

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

Wyoming showed that most species did change gradually through time. He also found that mammals from the Eocene-Oligocene (30-35 Mya) beds of the Big Badlands of South Dakota and related areas remained the same through millions of years and if spectated, they did so abruptly. They were stable even over an interval of climatic change. Such findings go well with the view of punctuated equilibrium, as advocated by Stephen Jay Gould and Niles Eldredge, as well as theistic views of creation.

Both groups of hoofed mammals became widespread due to major radiation between Europe and North America; along with carnivorous mammals like the Mesonyx. Early forms of other mammals appeared, including bats, proboscideans (animals with trunks), rodents, and marsupials (animals that are born young in an immature state and mature in a pouch). Older primitive forms of mammals became less important and rarely seen. Important land fauna fossil remains have been found in western North America, Europe, Patagonia, Egypt, and South-East Asia. Marine fauna is best known from South Asia and the southeast United States.(encyclopedia)

The oldest known fossils of most of the modern mammals appeared within a geologically brief period during the early Eocene. At the beginning several new mammal groups arrived in North America. The modern mammals were artiodactyls (hoofed animals with odd number of toes), perissodactyla’s (hoofed animals with an even number of toes), and primates(animals with opposable thumbs) they also had features like long, thin legs, feet, and hands capable of grasping, as well as differentiated teeth adapted for chewing. All the members of the new mammal orders were small, under ten kilograms; based on comparisons of tooth size, the mammals were only 60 percent of the size of the primitive Paleocene mammals that had come before them. They were also smaller than the mammals that came after them. Many think that the hot temperatures favored smaller animals because they could manage heat.

Antarctica, started with a warm temperate to sub-tropical rainforest, became much colder as the period went on ; the heat-loving tropical flora was wiped out, and by the beginning of the Oligocene the continent had deciduous forests and vast stretches of tundra.

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

Cooling began mid-period, and by the end of the Eocene continental interiors had begun to dry out. The forests were thinning out considerably in some areas. The new grasses were confined to river banks and lake edges.

Palm trees were growing as far as Alaska and northern Europe, but they became less and less abundant as the climate cooled.

Polar forests were extensive ,Fossils and preserved remains of trees such as swamp cypress and dawn redwood have been found in Ellesmere Island in the Canadian Arctic. The preserved remains found are not fossils, but actual pieces in oxygen-poor water in the swampy forests of the time, and that were buried before they had the chance to decompose. At that time, the Island was only a few degrees in latitude further south than it is today. Fossils of subtropical and even tropical trees and plants have also been found in Greenland and Alaska. Tropical rainforests grew as far as the Pacific Northwest and Europe.

As I said before the beginning of the Eocene had the highest temperatures and warmest oceans and they assumedly created a moist, mild environment, with forests spreading throughout the earth. Except the driest deserts, Earth must have been entirely covered in forests.

The Eocene epoch (meaning dawn of recent life) ranges from 54.8 million years ago to 33.7 million years ago. It is a part of the Paleogene period comes after the Paleocene epoch and before the Oligocene epoch. The SU and Yale research team found that average Eocene water temperature along the subtropical U.S. Gulf Coast hovered around 80 degrees Fahrenheit. and the modern temperatures in the study area average 75 degrees Fahrenheit (Astrobio 2011). This epoch is said to have started with lots of rain and no ice and said to have ended cool with ice forming. Earths continents were also moving closer to where they are today at this time.

The supercontinent Laurasia broke into the pieces that are known today as Europe, Greenland, and North America and the Rocky Mountains in western North America were also formed during this time. Gondwana another supercontinent which contained land that is now South America, Africa, India Australia and Antarctica had also broken apart, but Australia and Antarctica were still connected until around 45 million years ago when they split apart. Australia and India went north India eventually collided with Asia to create the Himalayan mountains. Africa and south America were both isolated continents (boone,corrie).