Humans think of themselves as the most important creatures ever to walk the planet. But when it comes to size, humans are mere peanuts next to ballpark-sized animals. Here's a snapshot — you never know what a paleontologist will dig up — of some of the biggest animals that have walked our planet, present and past.
Pictured here is the megalodon, also known as Carcharocles megalodon. This creature was a 52-foot shark with jaws big enough to swallow a rhinoceros. It lived about 25 to 1.5 million years ago. Some believers think it may still lurk in our deepest oceans today, though there is no proof of this. (Text: Katherine Butler)