Axial remains of a large ichthyosaur and a medium-sized anacoracid shark from the deep-water sediments of the Cenomanian of the Northern Apennines (Northern Italy) are described in detail. The specimens were found closely associated (less than 0.3 m apart), and offer an invaluable window into the taphonomy and dead-fall stages of pelagic vertebrates in a Mesozoic abyssal plain. The anacoracid shark remains, initially misinterpreted as an ichthyosaur, consist of eight articulated vertebrae embedded in a block of dark arenaceous matrix, and represent the first occurrence of an articulated shark from the Northern Apennines. The ichthyosaur remains consist of seven discoidal vertebrae and several unidentified fragments. Due to the absence of diagnostic skeletal elements, both specimens are assigned only at higher taxonomic levels. The two fossils, which come from the same outcrop and possibly from the same stratigraphic horizon, share a common taphonomic history, in terms of both their preservation and diagenesis. Mineralogy of the matrices of both is dominated by manganese micro-nodules, consistent with the deposition of polymetallic nodules in bathyal-abyssal settings. Biostratinomic processes that impacted the two specimens also provide insight on the development of Mesozoic marine vertebrate-falls in the deep-sea. Localized pyrite framboids inside the bone spongiosa are possible evidence of the sulfophilic stage (microbially mediated sulfur mobilization during lipid decay) in the ichthyosaur fall. Burrows assigned to Taenidium on the surface of the shark block, interpreted as worm-like feeding burrows or arthropod locomotion and feeding trails, might represent evidence of the enrichment opportunistic stage. Although intriguing, we have no evidence to support the hypothesis that this peculiar association of two pelagic predators is due to ecological interaction between the two animals.

As a biotic interaction, drilling predation is affected by the evolutionary histories of the predator and prey, as well as the environment. A unique location with distinctive evolutionary histories and environmental conditions is the remote island of Rapa Nui. For mollusks, an evolutionary history in relative isolation has led to high rates of endemism (35–40%), in an area that has some of the most nutrient-poor waters of the global ocean. Here, we use death assemblages collected in Rapa Nui to answer two main questions: (1) How does a pervasive interaction like drilling predation play out in an isolated, oligotrophic marine system? and (2) What role do the environment (exposed vs. sheltered sites) and species traits (feeding, mobility, life habit) play in ‘protecting’ the prey? We predicted that predation would be low relative to other tropical and subtropical islands given the oligotrophic conditions and found that the average drilling frequency (DF) was 5.67% (n = 6122). We observed no significant differences in DF between feeding guilds, mobility types, or life habits. Sheltered sites dominated by the infaunal bivalve Ctena bella had higher predation. In terms of passive defenses for C. bella, larger body size was not an effective defense against drilling predators. We show that drilling predation in Rapa Nui is lower than in high-latitude regions, and it is dependent on how sheltered or exposed sites are. Historically and currently, Rapa Nui has been subject to multiple anthropogenic stressors, including over-extraction and tourism, making efforts to understand its endemic species and their interactions fundamental.