Prehistoric penis worms shed light on ocean ecology half a billion years ago

Dr Tom Harvey from the Department of Geology has been involved in a study along with researchers at the University of Cambridge into Ottoia, a type of phallic-shaped ‘penis worm’ – and has helped to identify that the creature used a bizarre set of teeth to drag itself across the floor of the ocean around half a billion years ago.

Individual teeth derived from priapulid worms, preserved as microfossils extracted from Cambrian mudstones. The scale bar represents 50 µm. Image credit: Dr Tom Harvey, University of Leicester.

The creature was able to turn its mouth inside out to catch prey and to move itself around by its tooth-lined throat. The unique dental structure of Ottoia may help in the identification of previously unrecognised fossil specimens from the time on Earth when animals were first coming into their own. Furthermore, the discovery of identical (but disarticulated) Ottoia teeth among Cambrian microfossils points to an unanticipated ecological range.

Dr Harvey said: “Previously, Cambrian priapulid worms were known from only a handful of exceptional fossil localities. But now that we can identify their ‘teeth’ among isolated microfossils -which are much more widespread - we can map out the distribution of priapulids in Cambrian seas, shedding light on the ecology of the oceans half a billion years ago.”

The researchers examined fossils of Ottoia, a type of penis worm, about the length of a finger, which lived during the

The Cambrian fossil penis-worm Ottoia, from the Burgess Shale of western Canada. The front end of the animal bears an array of minute teeth and spines. This specimen measures around 8 cm in length. Image credit: Dr Martin Smith, University of Cambridge.

Cambrian. The fossils originated from the Burgess Shale in western Canada, among the world’s richest source of fossils from the period, full of exquisitely preserved but often enigmatic creatures that have helped scientists understand how animal life on Earth developed.

Electron microscopy was used to examine the fine structure of the teeth of these creatures, which first 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.

The research has been used to compile a ‘dentist’s handbook’ which has aided in the identification of microscopic fossilised teeth from a number of previously-unrecognised ‘penis worm’ species from all over the world.

The study was funded by Clare College, Cambridge, the Palaeontological Association, and the Natural Environment Research Council.

The paper, entitled ‘The macro- and microfossil record of the Cambrian priapulid Ottoia’ was published in Palaeontology and is available here.

• University of Cambridge press release