Fossil traces of Osedax in dense whale ear bones and thoughts on potential further food sources

Abstract An Oligocene whale ear bone (tympanic bulla) from western Washington State, USA, preserves traces made by the bone-eating marine annelid Osedax . The tympanic bullae of whales are comprised of super-dense, glassy bone and had earlier been hypothesized as being too solid and nutrient poor to attract or sustain Osedax . Computed tomography of the specimen, from an undetermined species of mysticete (baleen whale) and found in the Lincoln Creek Formation, revealed traces with two different morphologies resembling those made by extant Osedax . Sectioning and microscopic investigation of a different mysticete bulla from the Lincoln Creek Formation showed that the bulla is equally as dense as those of extant whales. Inspired by these observations, we discuss other collagen-bearing biomaterials such as shark cartilage, shark egg capsules, and even shells of lingulid and disciniscid brachiopods as potential, but as yet undocumented, additional sources of nutrients for Osedax .