Cenozoic Era

Following the extinction of the dinosaurs, the Cenozoic marks the beginning of a new era, generally referred to as "The Age of Mammals.” This is the period of time when the mammals grew to colossal sizes and began dominating the land. However, don’t be fooled: The avian dinosaurs survived and continue to thrive today. These are also known as birds.

Paleocene Epoch: 66 - 56 million years ago

Climate: Very hot and tropical

Famous Animals: Early ancestors of primates

About: The first epoch during the Paleogene period, the Paleocene epoch marks the end of the dinosaurs’ reign. Many different ecological niches that were suddenly empty were slowly repopulated by many new species of mammals.

Eocene Epoch: 56 - 33.9 million years ago

Climate: Extremely warm at first, then slowly became cooler and drier

Famous Animals: Titanotheres, and the first whales

About: The planet was very warm, allowing alligators and turtles to live in polar regions. The Rocky Mountains were volcanic, while the world’s first perissodactyls (odd-toed ungulates) evolved, relatives of modern rhinos, horses, and tapirs.

Oligocene Epoch: 33.9 - 23 million years ago

Climate: Cooler

Famous Animals: Entelodonts, and early horses

About: As South America pulled away from Antarctica, this allowed the ocean waters to cool significantly, and Antarctica’s ice cap continued to grow. Most of the forests in North America gave way to large, open grasslands. This also marked the end of the Paleogene period.

Miocene Epoch: 23 - 5.3 million years ago

Climate: Slightly warmer before cooling again

Famous Animals: Horses, rhinos and camels common in North America

About: The Bering Land Bridge, which once allowed animals to pass freely from North America to Asia, is flooded, temporarily cutting these landmasses off from one another. Early ancestors of elephants finally evolved and took many shapes.

Pliocene Epoch: 5.3 - 2.6 million years ago

Climate: Varied between cool/dry, to warm/wet, and back to cool/dry again

Famous Animals: Mastodons and mammoths are prevalent in many parts of the world

About: North and South America finally joined, resulting in massive migrations of animals from both continents. Many of the S. American species became extinct like giant sloths, but northern species likes bears and cats prospered. Meanwhile, in Africa, our earliest relatives continued to evolve.

Pleistocene Epoch: 2.6 - .0117 million years ago

Climate: Cooler, many cycles of glaciation occurred

Famous Animals: Homo sapiens, Neanderthals

About: The Pleistocene was a time of cooling, and as many as twenty different "Ice Ages” happened during this time. Modern humans also migrated from Asia to N. America during the latter part of this epoch. Many large species of mammals became extinct soon after, which is often attributed to the arrival of the humans.

Holocene Epoch: 11,700 years ago - present

Climate: Slight warming

Famous Animals: Lions, and tigers and bears, oh my!

About: The most recent of all epochs, the Holocene is what we are living in right now. We are in a period of time between substantial glaciation, and sea levels are rising gradually. Humans may have contributed to some of this warming.