Osedax fenrisi is a species of bone-eating worm in the family Siboglinidae, discovered on a whale carcass in the deep sea near Antarctica. This species is adapted to extreme environments, feeding on the lipids within whale bones through root-like structures that penetrate the bone. It relies on symbiotic bacteria housed in these root structures to metabolize the organic material. Named after the Norse god Fenrir, this species highlights the unique adaptations of deep-sea organisms to nutrient-limited habitats.