Penguins are a group of flightless semi-aquatic sea birds which live almost exclusively in the Southern Hemisphere. Only one species, the Galapagos penguin, lives at, and slightly north of, the equator. Highly adapted for life in the ocean water, penguins have countershaded dark and white plumage and flippers for swimming. Most penguins feed on krill, fish, squid and other forms of sea life which they catch with their bills and swallow whole while swimming. A penguin has a spiny tongue and powerful jaws to grip slippery prey. They spend about half of their lives on land and the other half in the sea. The largest living species is the emperor penguin (Aptenodytes forsteri): on average, adults are about 1.1 m (3 ft 7 in) tall and weigh 35 kg (77 lb). The smallest penguin species is the little blue penguin (Eudyptula minor), also known as the fairy penguin, which stands around 30–33 cm (12–13 in) tall and weighs 1.2–1.3 kg (2.6–2.9 lb). Today, larger penguins generally inhabit colder regions, and smaller penguins inhabit regions with temperate or tropical climates. Some prehistoric penguin species were enormous: as tall or heavy as an adult human. There was a great diversity of species in subantarctic regions, and at least one giant species in a region around 2,000 km south of the equator 35 mya, during the Late Eocene, a climate decidedly warmer than today.
Etymology The word penguin first appears in literature at the end of the 16th century as a synonym for the great auk. When European explorers discovered what are today known as penguins in the Southern Hemisphere, they noticed their similar appearance to the great auk of the Northern Hemisphere and named them after this bird, although they are not closely related. The etymology of the word penguin is still debated. The English word is not apparently of French, Breton or Spanish origin (the latter two are attributed to the French word pingouin), but first appears in English or Dutch. Some dictionaries suggest a derivation from Welsh pen, 'head' and gwyn, 'white', including the Oxford English Dictionary, the American Heritage Dictionary, the Century Dictionary and Merriam-Webster, on the basis that the name was originally applied to the great auk, either because it was found on White Head Island (Welsh: Pen Gwyn) in Newfoundland, or because it had white circles around its eyes (though the head was black). However, the Welsh word pen can also be used to mean 'end' and, in a maritime context, pen blaen means 'front end or part, bow (of a ship), prow'. An alternative etymology links the word to Latin pinguis, which means 'fat' or 'oil'. Support for this etymology can be found in the alternative Germanic word for penguin, fettgans or 'fat-goose', and the related Dutch word vetgans. A group of penguins in the water is sometimes called a raft.
Pinguinus
Since 1791, the Latin word Pinguinus has been used in scientific classification to name the genus of the great auk (Pinguinus impennis, meaning "plump or fat 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 Lucien Bonaparte in several distinct genera within the family Spheniscidae and order Sphenisciformes.
Systematics and evolution
Taxonomy
The family name of Spheniscidae was given by Charles Lucien Bonaparte from the genus Spheniscus, the name of that genus comes from the Greek word σφήν sphēn "wedge" used for the shape of an African penguin's swimming flippers. Some recent sources apply the phylogenetic taxon Spheniscidae to what here is referred to as Spheniscinae. Furthermore, they restrict the phylogenetic taxon Sphenisciformes to flightless taxa, and establish the phylogenetic taxon Pansphenisciformes as equivalent to the Linnean taxon Sphenisciformes, i.e., including any flying basal "proto-penguins" to be discovered eventually. Given that neither the relationships of the penguin subfamilies to each other nor the placement of the penguins in the avian phylogeny is presently resolved, this is confusing, so the established Linnean system is followed here. The number of penguin species is typically listed as between seventeen and nineteen. The International Ornithologists' Union recognizes six genera and eighteen species:
Evolution
Although the evolutionary and biogeographic history of Sphenisciformes is well-researched, many prehistoric forms are not fully described. Some seminal articles about the evolutionary history of penguins have been published since 2005. The basal penguins lived around the time of the Cretaceous–Paleogene extinction event in the general area of southern New Zealand and Byrd Land, Antarctica. Due to plate tectonics, these areas were at that time less than 1,500 kilometres (930 mi) apart rather than 4,000 kilometres (2,500 mi). The most recent common ancestor of penguins and Procellariiformes can be roughly dated to the Campanian–Maastrichtian boundary, around 70–68 mya.
Basal fossils The oldest known fossil penguin species are known from the Waipara Greensand of New Zealand, which spans the late Danian to early Thanetian stages (~62.5–58 Ma) of the Paleocene epoch. Several genera have been named from these outcrops, including Archaeodyptes, Daniadyptes, Muriwaimanu, Sequiwaimanu, Waimanu, Waimanutaha, and Waiparadyptes. While they were not as well-adapted to aquatic life as modern penguins, they were still flightless, with short wings adapted for deep diving. They swam on the surface using mainly their feet, but the wings were—as opposed to most other diving birds (both living and extinct)—already adapting to underwater locomotion. Perudyptes from northern Peru was dated to 42 mya. An unnamed fossil from Argentina proves that, by the Bartonian (Middle Eocene), some 39–38 mya, primitive penguins had spread to South America and were in the process of expanding into Atlantic waters.
… excerpt ends here. Continue reading the full article.
