Smithsonian National Museum of Natural History Geologic Time The Story of a Changing Earth
Presented by the Department of Paleobiology.
The Eocene
Eocene Overview
Terrestrial Life during the Eocene
Marine Life in the Eocene
Shifting Continents and Changing Climates
A fossil weevil from the Green River
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Dawn horse
Pseudocrypturus cereamaxis
Extinct whale
Snail shell
Fern leaf
Palm leaf
March fly

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Terrestrial Life during the Eocene
During the warmest part of the early Eocene, palm trees grew as far north as Alaska and Spitsbergen Island in the North Atlantic. Crocodilians lived above the Arctic Circle, and forests of dawn redwoods grew at 80° N latitude. As climate cooled and became more seasonal during the middle and late Eocene, forests gave way to dry woodlands, perhaps with open patches of grasses and herbs. The Eocene saw changes in the distribution of plants, as some species occupied new geographic regions. Most of the modern bird orders were present by the Eocene, as well as several unusual, now-extinct species. One, the North American Diatryma, was a flightless, six-foot-tall predator.

Herbivorous mammals were browsers, feeding on soft vegetation such as leaves and herbs, or selectively feeding on fruits and seeds. The first odd-toed hoofed mammals (perissodactyls, such as horses, tapirs, and rhinos) appeared at the beginning of the Eocene, as did the first even-toed hoofed mammals (artiodactyls, which included pig-like omnivores and camels). The largest mammals of the Eocene were the titanotheres; many species of these browsing perissodactyls lived in North America and Eurasia, but all were extinct by the end of the epoch. Another group of large hoofed mammals, the uintatheres, also evolved very large body size in the Eocene.

Alongside these new forms appeared the earliest members of our own order, the primates. It is not yet clear which continent these evolved on. Rodents began to diversify and possibly to compete with the multituberculates — a group of mammals with somewhat rodent-like incisors that first evolved in the Mesozoic. Multituberculates became extinct around the end of the Eocene. The first bats are known from the Eocene as well, and forms such as Icaronycteris were already very much like modern forms. Primitive Eocene carnivorans included the first members of the dog, weasel, bear, and cat families. By the end of the Eocene, holdovers from the Paleocene, such as condylarths, pantodonts, and uintatheres, had gone extinct, along with most of North America's primates .


Eocene Overview | Terrestrial Life during the Eocene | Marine Life in the Eocene
Shifting Continents and Changing Climates

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