About 24 million years ago, which really isn't all that long ago when you think about it, there lived a seal that looked a lot like the seals we can see today. But instead of flippers this seal had four legs! Check out what he might have looked like (drawing from the Canadian Museum of Nature.)
This guy was named Puijila Darwini, which means "Darwin's young marine mammal." Yup, he was named after our very own Charlie.
Take any mammal that lives in the sea, like seals, whales and dolphins. They all evolved from other earlier animals that lived on land and had four legs. As they gradually evolved to live in the sea, their legs gradually disappeared. This little seal shows us that process in action! He lived in the water but hadn't lost his legs yet.
Want to see a really cool interactive site about this animal? Click here.