So, they don't leave behind bony fossils like dinosaurs or humans would. So, when people find remnants of the ancient sharks that are that big, it's a big deal. Basak called the tooth a "unicorn ...

Known as the Siberian unicorn, the animal had a long horn on ... "And, of course, what we've also learned from the fossil record is that once a species is gone, that's it, it's gone for good." ...