Six years ago Osedax was first described based on specimens living on a whale carcass in 2891 m depth off California. Since then paleontologists have been searching for fossil evidence to pin down its geologic age. Now researchers at the Institute of Geosciences at the Christian-Albrechts-University at Kiel, Germany, found 30 Million year old whale bones with holes and excavations matching those of living Osedax in size and shape. The evidence of the boreholes and cavities made by the living worms was provided by Greg Rouse (Scripps Institution of Oceanography), one of the original discoverers of Osedax.
To produce accurate images of the fossil boreholes, the bones were CT-scanned by the scientists. The fossil bones belong to ancestors of our modern baleen whales and their age was determined using so-called co-occurring index fossils. “The age of our fossils coincides with the time when whales began to inhabit the open ocean” explains Steffen Kiel, who has been working on the evolution and fossil history of deep-sea ecosystems for many years. Only from the open ocean dead whales could sink to the deep-sea floor where they served as food for the boneworms. “Food is extremely rare on the vast deep-sea floor and the concurrent appearance of these whales and Osedax shows that even hard whale bones were quickly utilized as food source,” Steffen Kiel explains the relevance of their discovery.