Toothy 'Penis Worm' is the Stuff of Nightmares

This is bound to make any male cringe. Experts recently determined that the ancient 'penis worm,' Ottoia¬¬ - a phallus-like creature more than 500 million years old - boasted a throat lined with deadly razor and serrated teeth. In fact, these teeth were so varied and numerous that researchers crafted a "dentists' handbook" to help them identify new species in the genus.