Specialist diets have been identified amongst elasmobranch, although the degree of specialization can be subjected to individual specialists, competition, and fluctuations in spatial and temporal prey abundance and availability. Several examples of chondrichthyans playing a large role in diet of other chondrichthyans have been previously documented, although few are known from the deep-sea, and have included large bodied species. The prickly dogfish, Oxynotus bruniensis, is a small (< 75 cm), little known deep-sea elasmobranch distributed on the outer continental and upper slope of southern Australia and New Zealand. Specimens (n = 53) were collected from research trawls surveys and fisheries observers from around New Zealand at depths from 400 to 1300 m. Stomach contents were dissected and prey items were identified to the lowest possible taxon. Findings included Harriotta raleighana embryos and vitellus from unknown origin. 15 stomach samples were analysed with DNA methods, revealing that O. bruniensis preys exclusively on the egg capsules of oviparous chondrichthyans, including Rhinochimaera pacifica and Chimaera carophila. These are the first results of a wild elasmobranch sample relying solely on other chondrichthyans as a food source. In addition to its low reproductive output and high distribution overlap with fishing efforts, the reliance on a specialized diet may make O. bruniensis a particular vulnerable species to overfishing.