for penguin, or 'fat-goose', and the related Dutch word . Adult male penguins are called cocks, females are hens; a group of penguins on land is a waddle, and a group of penguins in the water is a raft. Pinguinus Since 1871, the Latin word Pinguinus has been used in scientific classification to name the genus of the great auk (Pinguinus impennis, meaning "penguin without flight feathers"), which became extinct in the mid-19th century. As confirmed by a 2004 genetic study, the genus Pinguinus belongs in the family of the auks (Alcidae), within the order of the Charadriiformes. The birds currently known as penguins were discovered later and were so named by sailors because of their physical resemblance to the great auk. Despite this resemblance, however, they are not auks, and are not closely related to the great auk. They do not belong in the genus Pinguinus, and are not classified in the same family and order as the great auk. They were classified in 1831 by Charles Bonaparte in several distinct genera within the family Spheniscidae and order Sphenisciformes. Systematics and evolution Living and recently extinct species The number of extinct penguin species is debated. Depending on which authority is followed, penguin biodiversity varies between 17 and 20 living species, all in the subfamily Spheniscinae. Some sources consider the white-flippered penguin a separate Eudyptula species, while others treat it as a subspecies of the little blue penguin; the actual situation seems to be more complicated. Similarly, it is still unclear whether the royal penguin is a separate species or merely a color morph of the macaroni penguin. The status of the rockhopper penguins is also unclear. Updated after Marples (1962), Acosta Hospitaleche (2004), and Ksepka et al. (2006). Subfamily Spheniscinae – modern penguins Fossil genera Order Sphenisciformes Basal and unresolved taxa (all fossil) Anthropodyptes (Middle Miocene) Arthrodytes (San Julian Late Eocene/Early Oligocene – Patagonia Early Miocene of Patagonia, Argentina) Aprosdokitos Hospitaleche, Reguero & Santillana 2017 Crossvallia (Cross Valley Late Paleocene of Seymour Island, Antarctica) Ichthyopteryx Wiman 1905 Kupoupou (Late Early-Middle Paleocene of Takatika Grit, New Zealand) Kaiika Fordyce & Tomas 2011 (Maxwell's penguin) Korora (Late Oligocene of S Canterbury, New Zealand) Inguza (Late Pliocene) Muriwaimanu (Late Paleocene of Canterbury, New Zealand) Nucleornis (Early Pliocene of Duinfontain, South Africa) Orthopteryx Wiman 1905 Palaeoapterodytes (Late Oligocene/Early Miocene of Argentina) Pseudaptenodytes (Late Miocene/Early Pliocene) Sequiwaimanu (Late Paleocene) Tasidyptes Van Tets & O'Connor