Mama, Look at the Mammals!

Beginning about 65 million years ago, mammals started to become more plentiful.  At first, these creatures were small, mostly insect eating creatures.


Illustration of Arctocyon Credit: D. Bogdanov

These animals had the beginnings of hoofs and claws.   Over time, mammals became larger.


Illustration of Barylambda faberi, a pantodont from the Paleocene of North America

From 54 to 33 million years ago, ancestors of deer, sheep, zebra,  and cows were present.  One example of this was a small rabbit sized animal.

From 24 to 5 million years ago, mammals became faster moving species.  Rodents, or mammals like today’s squirrels or rats, developed. This coincided with a dryer climate, which caused more open grasslands to develop as well.

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