Prehistoric animals once roamed — and ruled — planet ... Though vastly different, they all died out in similar ways due to changing climate, poaching, or disease. Today, they exist as just ...

With many varieties and sizes—they ranged from a millimeter to more than 2 feet (0.6 meters) in length—trilobites proved among the most successful and enduring of all prehistoric animals.

Our earliest mammalian ancestors avoided the dominant dinosaurs by only coming out at night and having uniformly dark, ...