An international team of scientists led by paleontologist Steffen Kiel at the Christian-Albrechts-University at Kiel, Germany, and Scripps Institution of Oceanography at UC San Diego, have found the first fossil boreholes of the worm Osedax inside ancient whale bones on the deep-sea floor. In a research paper published in the current issue of the scientific journal Proceedings of the National Academy of Sciences, the scientists conclude that "boneworms" are at least 30 million years old.
Six years ago Osedax was first described by Monterey Bay Aquarium Research Institute scientists based on specimens discovered living on a whale carcass at 2,891 meters (9,484 feet) depth off California. Since then paleontologists have been searching for fossil evidence to pin down Osedax's geologic age. Now, researchers at the Institute of Geosciences at the Christian-Albrechts-University at Kiel 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 in contemporary whalebones by Osedax was provided by Scripps Professor Greg Rouse, one of the original describers of Osedax. Rouse provided key data on the size and shape of the surface holes that boneworms make, as well as dissections showing the cavities they bore beneath the bone surface.
The fossil bones used in the study belong to ancestors of modern baleen whales and their age was determined using co-occurring index fossils. To produce accurate images of the fossil boreholes, the bones were CT-scanned by the scientists.
"The age of our fossils coincides with the time when whales began to inhabit the open ocean," said Kiel, who has been working on the evolution and fossil history of deep-sea ecosystems for many years. Dead whales sink to the deep-sea floor where they serve as food for 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 a food source," Kiel said.
The ancient bones were found by American fossil collector Jim Goedert, who has been collecting fossils along the American Pacific coast for more than 30 years.
Kiel and Goedert have conducted several field trips to the U.S. Pacific Coast, a geologically active area where fossil-rich sediments are continuously uplifted by plate tectonic processes. The fossils have now found their final home at the Burke Museum in Seattle, Wash., which also was involved in the current research paper, and at the Smithsonian Natural History Museum in Washington, D.C.
Dr. Steffen Kiel
Christian-Albrechts-University at Kiel
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