First trace-fossil evidence of bone-eating worms in whale carcasses

Whale corpses on the modern seafloor host particular communities that benefit from the large amounts of available labile organic matter. The study of these communities has revealed the presence of the siboglinid annelid Osedax that feeds on bone tissue by means of a symbiotic relationship with heterotrophic bacteria. Here we report the presence of tubular borings in a fragment of the neurocranium of a fossil baleen whale found in lower Pliocene rocks of southeastern Spain. They are formally described as Trypanites ionasi isp. n. The fossil borings can be assigned to annelid or sipunculid worms and may constitute the first evidence of an Osedax-like osteophagous behavior in the fossil record of cetaceans. Nevertheless, the definitive assignment to Osedax is not possible until we have more information on the morphology of modern siboglinid borings.