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Intro | Precambrian Eon | Paleozoic Era | Mesozoic Era | Cenozoic Era

Cenozoic Era: (248 mya-present)

Paleocene | Eocene | Oligocene | Miocene | Pliocene | Pleistocene | Holocene

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Paleocene Epoch (65-54 mya)

The Paleocene epoch marks the beginning of the Cenozoic era and the Tertiary period. Dense forests grow in the warm, damp, and temperate climate. Ferns, horsetails, and shrubby flowering plants make up the underbrush, while sequoias, pines, and palms grow tall, some to towering heights. Sea level has fallen, exposing much of continental North America, Africa, and Australia.

In the oceans, invertebrates increasingly resemble modern forms. Squid, for example, which lack shells, take the place of ammonites as the dominant cephalopod form. Ammonites died out in the Cretaceous extinction. Among the vertebrates, sharks and bony fishes flourish.

Mammals fill terrestrial niches left open following the end-Cretaceous extinction, migrating between continents that remain joined: Europe, Asia, and North America in the northern hemisphere, and Australia, South America, and Antarctica in the southern hemisphere. Paleocene mammals are still small and exhibit few characteristics of later forms, like swiftness and specialized teeth. For much of the epoch, lizards, snakes, and crocodiles are among the larger predators. Before epoch's end, however, Diatrymiformes -- giant, predatory, flightless birds -- are common in the northern hemisphere.

65 mya: Tropical climate extends to polar regions

With a warm and steady climate, tropical conditions extend from pole to pole. Deciduous (non-evergreen) forests cover lands in the north and south, and animals pass freely from continent to continent, unhindered by ice.

60 mya: Primates

While primates may have evolved several million years earlier, the oldest confirmed primate fossils date to about 60 mya. Early primates -- resembling lemurs or tarsiers -- probably live in trees in tropical or subtropical areas. Many of their characteristic features are well suited for this habitat: hands specialized for grasping, with five digits and, in most primates, opposable thumbs; rotating shoulder joints; and stereoscopic (three-dimensional) vision. Other traits include a large brain cavity and nails instead of claws. Members of the primate order, which are typically placed among the prosimian or anthropoid ranks, range in size today from the pygmy mouse lemur to the gorilla.

57 mya: Rodents

Rodents, which probably evolve in Asia, are the most abundant and adaptable group of mammals. They live in trees, underground, in water, and in deserts on every continent except Antarctica. All rodents -- including mice, rats, squirrels, and beavers -- have very hard, ever-growing front teeth suited for eating a variety of seeds and grains. The distribution of rodent fossils gives clues to their migratory patterns, which, in turn, helps scientists reconstruct past global climates.

55 mya: Bats

Bats, which are the only mammals capable of sustained flight, first appear in the fossil record 55 mya. Because light skeletons and paper-thin wings don't preserve well over time, teeth are all that remain of Paleocene bats. Bats' wing structure differs from both pterosaurs and birds. Elastic, membranous wings stretch between arm, body, and leg. Also, their fingers open out toward the wingtip, like a fan. Because the hind leg is not free for other uses such as walking, bats adopt some unusual habits, such as hanging upside down to rest. Today, bat species make up one-quarter of all mammalian species.

-> Go to the Eocene Epoch

Intro | Precambrian Eon | Paleozoic Era | Mesozoic Era | Cenozoic Era

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