The Extreme Mammals Image Gallery

Tiny Horsey
Encyclopaedia Britannica/UIG/Getty

Hyracotherium: Also known as the Dawn Horse, this most ancient of all horses (35 million years ago) was a mere 8-inches-tall (20 cm) at the shoulder and a foot long. Plus, they had weird feet: four toes in the front, three in the back.

About the Author: Robert Lamb spent his childhood reading books and staring into the woods — first in Newfoundland, Canada and then in rural Tennessee. There was also a long stretch in which he was terrified of alien abduction. He earned a degree in creative writing. He taught high school and then attended journalism school. He wrote for the smallest of small-town newspapers before finally becoming a full-time science writer and podcaster. He’s currently a senior writer at HowStuffWorks and has co-hosted the science podcast Stuff to Blow Your Mind since its inception in 2010. In his spare time, he enjoys traveling with his wife Bonnie, discussing dinosaurs with his son Bastian and crafting the occasional work of fiction.