More than 99 percent of all species that have lived on Earth are now extinct. Sometimes extinctions actually accelerate the evolution of life on Earth. As some forms of life weaken and die off, they create opportunity for other species to grow and flourish. Take a look at these creatures and imagine what life would be like if they had survived!
The Shark Eater: Dunkleosteus
During Earth's "Age of Fishes" 400 million years ago, Dunkleosteus was a genuine sea monster. This aggressive predator, more than 11 feet in length with a skull two feet long, was armor-plated. Instead of mere teeth, it had two long bony blades that snapped and crushed its prey. Dunkleosteus dined on all kinds of seafood including early sharks, which didn't have a chance to diversify and grow to great sizes until Dunkleosteus went extinct about 360 million years ago.
Credit: WikiCommons/Arthur Weasley/UC Berkeley
International Year of Planet Earth 
