Imagine this. It's 50 million years ago, and you are having a nice day on the beach in the south of England. A giant shadow passes over the sand castle you're building. You look up to see... a cloud?... a plane?... no, it's an absolutely gigantic GOOSE!
Behold the Dasornis, an ancient waterbird whose wings were 16 feet across. Holy cow, that's big. Scientists think it is an ancestor of the geese we see today.
But it gets weirder. A new fossil shows that Dasornis had sharp teeth along its huge beak.
Wait. Teeth!? A monster goose with teeth? This takes some explaining.
You probably know already that birds evolved from dinosaurs, and that dinosaurs could have some pretty ferocious teeth. But as birds evolved they lost their teeth, probably to save weight so they could fly better. By about 100 million years ago, ancient birds had no teeth at all, and their descendents still don't today. But this guy, Dasornis, later RE-evolved sharp spikes in its beak to help it catch fish by skimming along the water. These spikes looked like teeth and acted like teeth, though they aren't made out of bone. Like the Dasornis' whole beak, the teeth were made of keratin, the same stuff your fingernails are made of.
I guess teeth are pretty handy for some animals, and they'll evolve 'em out of whatever they can!
The illustration is from the Senckenberg Research Institute and Natural History Museum.