Evidence of Osedax worm borings in Pliocene (∼3 Ma) whale bone from the Mediterranean

Osedax worms subsist entirely on vertebrate skeletons on the seafloor, using root-like tissues to bore into and degrade the bones. Paleontologists have only recently begun to appreciate the possible destructive effect that these worms may have had on the marine vertebrate fossil record and little is known of their evolutionary history. Using microcomputed tomography, we document Osedax-like borings in a fossil whale bone from the Pliocene of Italy and present new data on the borings of extant Osedax worms. The fossil borings are distinguished from those of other known borers and identified as traces of Osedax activity based on diagnostic features. Our results suggest that it is necessary to isolate individual borings for the confident identification of Osedax traces. This is only the second paleogeographic occurrence of Osedax in the fossil record and indicates that by the Pliocene these worms had colonised a large portion of the world's oceans. This is the first evidence for Osedax in the Mediterranean, past or present, and suggests that more species await discovery in this region.