Researchers from the University of Cambridge have made an important breakthrough in the study of penis worms that lived 500 million years ago.

Ancient penis worms, also known as priapulids, lived during the Cambrian explosion, a period when most major animal groups first appeared in fossil records.

Scientists have been studying the fossilized remains of their teeth to track the previously-unrecognized creature around the world. They used resolution electron and optical microscopy to reconstruct the teeth of penis worms, in minute detail.

Their study has led to the development of a ‘prehistoric dentists handbook’ that could help identify new specimens from the Cambrian period.

They had a tooth-lined throat resembling a cheese grater and could turn its mouth inside out to drag itself through the ancient sediment. The scientists reconstructed the teeth of the penis worm which enabled them to identify a number of previously unknown species from across the globe.

The teeth came in a variety of shapes such as cone, bear claw, and some that even resembled a city skyline. Although penis worms still exist today, they have been pushed to the margins of life. They generally reside in extreme underwater environments.

Due to their soft bodies that decay quickly, these types of early creatures have been extremely hard to study. However, these species were fearsome predators 500 million years ago.

Their teeth allowed it to feast on anything that crossed its path, including worms, shrimp and other marine animals despite its exclusively on penises.

In this recent study, the researchers looked at a type of penis worm called Ottoia. The fossils came from Burgess Shale in Western Canada that holds a treasure trove of preserved ancient creatures.