Become a Wyoming Junior Paleontologist

The Stunning Cenozoic

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We're almost done! It's time to learn about the Age of Mammals. The Cenozoic Era is actually the most recent geological era. The word itself comes from the Greek words "kainos" which means "recent" and "zoic" which means "life."

Why do you think scientists named this era "Recent Life?"

Mammals during the Mesozoic Era (Age of Dinosaurs) weren't very big! The biggest were only the size of racoon. This all changed during the Cenozoic Era. Mammals started to evolve from their tiny ancestors into all sorts of funny shapes and sizes. You might have heard of mammoths, they were big! But did you know beavers were human sized? Or that there were giant sloths twice as big a a grown-up?

A side-by-side comparison of a modern beaver, a human male (in this case, Justin Bieber) and a giant bear-sized beaver from 10,000 years ago during the Pleistocene of the Cenozoic. Illustration by Scott Woods/Western University.

Mammals weren't the only things to change. The climate itself also went through lots of funny changes as well -- from hot and tropical to chilly and icy! In Wyoming, it was so warm that we once had monkeys, crocodiles, and even cheetahs living here, but it eventually became so cold that the top half of North America was covered in a real thick layer of ice that was up to 2 miles high called a glacier. Brrr!

Take a look at the map below showing the USA during the Pleistocene.

Map of what the USA would have looked like in the Pleistocene, about 20,000 years ago.

Take a look at the map above. The color white shows areas of the USA that were covered by a glacier.

The state of Minnesota is outlined in blue. Was it under a glacier?

What about Wyoming outlined in red, were there glaciers in Wyoming during the Pleistocene? If so, did they cover the entire state?

Move on to complete Challenge #7.