Ancient flesh-eating ‘penis worm’ dragged itself around by teeth
It sounds like something out of a Frank Herbert fantasy novel, but flesh-eating ‘penis worms’ roamed the Earth 500 million years ago.
The creature was able to turn its mouth inside out and use its tooth-lined throat – which resembled a cheese grater – to drag itself around the Cambrian world.
Unlike the monsters in Herbert’s novel Dune, these creatures were only the size of a finger, and lived in burrows under the sea.
However they were voracious predators, gobbling up anything that crossed their path, including worms, shrimp and other marine creatures.
The phallic-shaped animals, officially known as priapulids, emerged during the ‘Cambrian explosion’, a period of rapid evolutionary development about half a billion years ago, when most major animal groups first appear in the fossil record.
Scientists at the University of Cambridge have been studying fossil remains of their teeth to work out how far penis worms spread across the world.
During the Cambrian, most animals were soft-bodied, like worms and sponges. Therefore, outside of the few very special places where conditions are just right to enable preservation of soft-bodied creatures, it is difficult to know for certain how far certain species were distributed.
The teeth of the ‘penis worms’ had different shapes according to their function: some were shaped like a cone fringed with tiny prickles and hairs, some were shaped like a bear claw, and some like a city skyline.
But they are so tiny that they had previously been misidentified as spores. Now that the teeth can be identified, it proves that the worms inhabited certain areas.
“As teeth are the most hardy and resilient parts of animals, they are much more common as fossils than whole soft-bodied specimens,” said Dr Martin Smith, a postdoctoral researcher in Cambridge’s Department of Earth Sciences and the paper’s lead author.
“But when these teeth – which are only about a millimetre long – are found, they are easily misidentified as algal spores, rather than as parts of animals. Now that we understand the structure of these tiny fossils, we are much better placed to a wide suite of enigmatic fossils.”
Penis worms still exist today and live in the sediment of ocean beds.
These teeth were not just used for eating food, however. By turning their mouths inside out, penis worms could also use their teeth sort of like miniature grappling hooks, using them to grip a surface and then pull the rest of their bodies along behind.
“Modern penis worms have been pushed to the margins of life, generally living in extreme underwater environments,” added Dr Smith. “But during the Cambrian, they were fearsome beasts, and extremely successful ones at that.”
For this study, the researchers examined fossils of Ottoia, a type of penis worm, about the length of a finger, which lived during the Cambrian.
The fossils originated from the Burgess Shale in Western Canada, the world’s richest source of fossils from the period.
Using high resolution electron and optical microscopy, they were able to expose the curious structure of Ottoia’s teeth for the first time.
By reconstructing the structure of these teeth in detail, the researchers were then able to identify fossilised teeth of a number of previously-unrecognised penis worm species from all over the world.
“Teeth hold all sorts of clues, both in modern animals and in fossils,” said Dr Smith.
“It’s entirely possible that unrecognised species await discovery in existing fossil collections, just because we haven’t been looking closely enough at their teeth, or in the right way.”
The study was funded by Clare College, Cambridge, the Palaeontological Association, and the Natural Environment Research Council.The research was published in the journal Palaeontology.