Disentangling deep-time evolution using preserved palaeoecological interactions: A temporal and biogeographic expansion of the bone-eating worm Osedax

Large vertebrate falls are an important source of food to benthic invertebrates. A variety of invertebrates are found in association with these carcasses both in the fossil record and today. The focus of this work is on marine reptiles from the Jurassic (beginning ~200 million years ago [Ma]) up until the Cretaceous-Paleogene boundary (K-Pg, ~66 Ma) and on large marine cetaceans from their origins ~50 Ma in the early Eocene up until the present day, and therefore covers a time range of ~200 Ma to the present. Invertebrate bioerosion on bone is not commonly described and this work therefore aims to expand this record, examining fossil marine reptiles for more generalised bioerosion, and both marine reptiles and cetaceans for instances of Osspecus, the trace fossil left by the highly adapted bone-eating worm Osedax. The emphasis of this thesis is on disentangling the diversity and distribution through time of this unique taxon. Initial results from the examination of marine reptile bone from the UK expanded the known instances of invertebrate bioerosion in bone by an order of magnitude. Some of this bioerosion was determined to be Osedax borings, and identified and described through CT-scanning, which expanded the Cretaceous biogeography of Osedax and provided the groundwork for an ichnotaxonomic system to classify these borings and use them as an analogue for past phylogenetic diversity. This preliminary system was then applied to marine specimens from the UK, and seven ichnospecies formally named, allowing for an inference of high Osedax diversity in the Cretaceous. Another ichnospecies was then described in fossil whale teeth, and additional borings found in the earliest known cetacean example. These results cumulatively apply a wide range of methods to expand on the known diversity and biogeography of Osedax in the fossil record and apply a taxonomic system to the findings