8 Extinct Wonders of the Animal Kingdom

Steller's Sea Cow (Hydrodamalis gigas): This massive marine mammal, related to the manatee and dugong, grew up to 30 feet long and weighed up to 10 tons. It had a small head, no dorsal fin, and flippers that resembled paddles. Discovered in the 18th century, it was quickly hunted to extinction within 27 years of its discovery.