penis worm teeth
Penis worms had teeth inside their throats like cheese gratersTom Harvey

A fearsome penis worm species that lived hundreds of millions of years ago had a tooth-lined throat resembling a cheese grater, scientists have discovered.

The creature, Ottoia, is known from 500-million-year-old fossils and measured about 8cm in length. They were burrowers that moved through sediment hunting down prey.

It is believed to have feasted on creatures similar to mollusks and tended to swallow them head first, however evidence of cannibalism has also been found – a trait found in penis worms living today.

penis worm
Reconstruction of the Penis Worm Ottoia in its burrow.Smokeybjb

"Modern penis worms have been pushed to the margins of life, generally living in extreme underwater environments," said lead author Martin Smith. "But during the Cambrian, they were fearsome beasts, and extremely successful ones at that."

The creature could turn its mouth inside out, revealing its tooth-lined throat. Researchers from the University of Cambridge and the University of Leicester have now used high-powered microscopes to find out more about the structure of their teeth.

Publishing their findings in the journal Palaeontology, scientists said the teeth – which measure less than 1mm in size – had a scaly base and were fringed with tiny prickles and hairs.

penis worm fossil
Ottoia worm lived 10 million years agoMartin_Smith

Scientists say that by reconstructing the penis worm's teeth, they found fossil teeth from previously unrecognised penis worm species from across the globe.

"Taken together, our study has allowed us to compile a 'dentist's handbook' that will help palaeontologists recognise a range of early teeth preserved in the fossil record," said Smith.

Concluding, the authors wrote: "The new morphological details resolved from the Burgess Shale combine to provide a distinctive search image for the recognition of Ottoia at both a macroscopic and microscopic level, setting the stage for future ... discoveries to establish the full breadth of this ecologically tolerant and locally prolific Cambrian worm."