The Great Auk, Pinguinus impennis, formerly of the genus Alca, was a large, flightless alcid that became extinct in the mid-19th century. It was the only modern species in the genus Pinguinus, a group of birds that formerly included one other species of flightless giant auk from the Atlantic Ocean region. It bred on rocky, isolated islands with easy access to both the ocean and a plentiful food supply, a rarity in nature that provided only a few breeding sites for the auks.