The Paleocene Epoch (meaning "early dawn of the recent") starts both the Cenozoic Era and Tertiary Period some 65 million years ago and extended until 55 million years ago. Following the mass extinctions at the end of the Cretaceous Period, mammals became the dominant land-living lifeform.
By the Paleocene the North American continent had attained roughly its modern outline. The climate was much milder and more uniform than present.
Classic Fossil-Bearing Sites
Sentinel Butte Formation, Western U.S.
Black Mingo Formation, S. Canada
Aquia Formation, Eastern U.S.
An enormous (200 km) craterform structure just north of the Yucatan Peninsula in Mexico is most likely the "dino killing" event that ended the Cretaceous. Another, much smaller crater (25 km) was produced near the same time near Kamensk, Russia. Two other impacts of approximately the same age (57 mya) are found in Russia as well. One of these is 60 km in diameter, while the other spans 25 km.
It was during the Paleocene that some common plant forms first appeared: the pines, the cacti, and the palms.
Bird Expansion Begins
During the Paleocene, birds began to diversify and occupy new niches. Most bird types had appeared by the middle Cenozoic, including representatives of perching birds, cranes, hawks, pelicans, herons, owls, ducks, pigeons, loons, and woodpeckers.
No Paleocene pictures are available at this time.