The grey notothen (Lepidonotothen squamifrons) and the mackerel icefish (Champsocephalus gunnari) (Notothenioidei; Perciformes; Teleostei) are two Southern Ocean acellular boned fishes whose bones show cyclical growth marks. The degree of mineralization of their bony tissues, respectively 1.06 to 1.39 gHA/cm3 and 1.04 to 1.33 gHA/cm3, is close to the values of better known acellular boned fishes like the wolffish, the anglerfish or the horse mackerel. The histological characteristics of bony tissues are not fundamentally different from those observed in other marine acellular boned fishes.