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.

A report recently published in the journal Paleontology describes how fearsome a beast the nightmarish 'penis worm' - that's what experts seriously call it - really was. When the phallic worm found some tasty prey, usually the shelled creatures known as hyolithids, it could invert its tube-like mouthpart to reveal rows and rows of serrated teeth and spines.

[Check out a nightmarish video simulation of the creature in action here.]

The prey was then quickly shredded and dismemberd, as suggested by a detailed analysis of about 40 Ottoia prolifica fossils collected by the Smithsonian Institution and 70 more specimens provided by the Royal Ontario Museum. The fossils reportedly were unearthed at dig-sites in the Upper and Lower Walcott Quarries, in the Canadian Rockies, respectively.

The investigation revealed that the teeth of these worms had a scaly base and were fringed with tiny prickles and hairs. (Scroll to read on...)

By reconstructing what the penis worm's teeth looked like, the researchers discovered fossil teeth from a number of previously unrecognized penis worm species all over the world. One species in particular, O. tricuspida, may have even been an infamously cannibalistic variety.

"Taken together, our study has allowed us to compile a 'dentist's handbook' that will help paleontologists recognize a range of early teeth preserved in the fossil record," Martin Smith, lead author of the study, explained in a statement.

Why any man would want to study cannibalistic, tooth-filled, phallic worms, however, remains a mystery that may never be solved.

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