First record of the little-known family Katianiridae Svavarsson, 1987 (Crustacea, Isopoda, Asellota) from the Southwest Atlantic Ocean, with description of two new species.

For the first time, species of Katianiridae are recorded from the Southwest Atlantic Ocean: Natalianira bicornuta sp. nov. from the Mar del Plata submarine canyon and Natalianira megalocera sp. nov. from the Marine Protected Area Namuncurá-Burdwood Bank are described. Both species can be distinguished from Natalianira spinosa Kensley, 1984, the only currently known species of this genus, by having (1) distal margin of the first article of the antennula produced, (2) a single row of mid-dorsal bumps on the pereonites 1-7, and (3) uropods distinctly extending beyond the posterior margin of the pleotelson. The geographic and bathymetric ranges of the genus Natalianira are extended.