Monday, 31 October 2011

Trace Fossils In Ancient Whale Bones Hint At An Undiscovered Species Of Worm

Zombie worms feeding upon a rotting whale carcass
Zombie worms are a family of annelids which bore into the bones of cadavers with root-like tentacles, dissolving the soft tissues and absorbing the nutrients. The most common genus is Osedax, containing five species. However fossil evidence suggests that there may be a completely unknown species living in the depths of the Mediterranean Sea.

The fossil in question is one of those fantastic 'back room' discoveries; not found in a remote quarter of a desert, but simply rediscovered, sitting under a layer of dust in the vaults of a museum.

The fossilised whale bone rediscovered
at the Florence Natural History Museum
The specimen was a section of whale bone discovered in 1875. Due to its poorly preserved and rather drab nature, it was consigned to a box in the store rooms of the Florence Natural History Museum, Italy. It was rediscovered by Dr Nicholas Higgs. Higgs was investigating the Osedax worms and made contact with scientists at the Natural History Museum, Florence, in order to examine the boreholes made by the annelids.

Higgs found no specimens which displayed the correct markings. Yet after a week he found a fossil. A full CT scan confirmed the presence of boreholes made by zombie worms which were very similar to modern day species. While fossil zombie worms are very rare (their soft bodied nature makes preservation very unlikely) their distinctive feeding traces are far more common. What makes this specimen interesting is that it was discovered in the Mediterranean.

No zombie worms or their feeding traces had been found in the Mediterranean, either in the modern day or fossil record. This find shows that such annelids are far more diverse than previously thought. It also made Dr Higgs think that there may be a completely new species of zombie worm on Earth, descended from the owners of the feeding traces. As the traces are not quite the same as known examples, the evidence does point towards a new species.