Penguin
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{{Taxobox
| name = Penguins
| fossil_range = [[Paleocene]]-Recent
| image = Pygoscelis papua.jpg
| image_width = 250px
| image_caption = [[Gentoo Penguin]], ''Pygoscelis papua''
| regnum = [[Animal]]ia
| phylum = [[Chordata]]
| classis = [[Aves]]
| infraclassis = [[Neognathae]]
| ordo = '''Sphenisciformes'''
| ordo_authority = [[Richard Bowdler Sharpe|Sharpe]], 1891| familia = '''Spheniscidae'''
| familia_authority = [[Charles Lucien Jules Laurent Bonaparte|Bonaparte]], 1831
| subdivision_ranks = Modern [[genus|genera]]
| subdivision =
''[[Aptenodytes]]''<br>
''[[Eudyptes]]''<br>
''[[Eudyptula]]''<br>
''[[Megadyptes]]''<br>
''[[Pygoscelis]]''<br>
''[[Spheniscus]]''<br>
For prehistoric genera, see [[Sphenisciformes#Systematics|Systematics]]
}}
[[Image:AntarcticaSummer.jpg|right|thumb|242px|A penguin encounters a [[human]] during Antarctic summer.]]
'''Penguins''' ([[order (biology)|order]] '''Sphenisciformes''', [[family (biology)|family]] '''Spheniscidae''') are a group of [[Aquatic animal|aquatic]], [[flightless bird|flightless]] [[bird]]s living almost exclusively in the [[Southern Hemisphere]].
The number of 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 Penguin]]; <ref name="Williams>Williams, (1995).</ref><ref name="Davis & Renner">Davis & Renner, (2003).</ref> the actual situation seems to be more complicated.<ref name="Banks">Banks ''et al.'' (2002).</ref> Similarly, it is still unclear whether the [[Royal Penguin]] is merely a color morph of the [[Macaroni penguin]]. Also eligible to be a separate species is the Northern population of [[Rockhopper Penguin|Rockhopper penguins]].<ref name="Davis & Renner"/> Although all penguin species are native to the southern hemisphere, they are not, contrary to popular belief, found only in cold climates, such as [[Antarctica]]. In fact, only a few species of penguin actually live so far south. At least 10{{Verify source|date=May 2007}} species live in the [[temperate]] zone: one; the [[Galápagos Penguin]]; lives as far north as the [[Galápagos Islands]].
The largest living species is the [[Emperor Penguin]] (''Aptenodytes forsteri''): adults average about 1.1 m (3 ft 7 in) tall and [[mass|weigh]] 35 kg (75 lb) or more. The smallest penguin species is the [[Little Penguin|Little Blue Penguin]] (also known as the Fairy Penguin), which stands around 40 cm tall (16 in) and weighs 1 kg (2.2 lb). Among extant penguins larger penguins inhabit colder regions, while smaller penguins are generally found in temperate or even tropical climates (''see also'' [[Bergmann's Rule]]). Some [[prehistoric]] species attained enormous sizes, becoming as tall or as heavy as an adult human (see below for more). These were not restricted to Antarctic regions; on the contrary, [[subantarctic]] regions harboured high diversity, and at least one giant penguin occurred in a region not quite 2,000 km south of the [[Equator]] 35 [[mya (unit)|mya]]<!-- the distance is accurate for 35 million years ago; it is closer to the equator today -->, in a climate decidedly warmer than today.
Most penguins feed on [[krill]], [[fish]], [[squid]], and other forms of [[sealife]] caught while swimming underwater. They spend half of their life on land and half in the oceans.
Penguins seem to have no special fear of humans and have approached groups of explorers without hesitation. This is probably on account of there being no land predators in [[Antarctica]] or the nearby offshore islands that [[prey]] on or attack penguins. Instead, penguins are at risk at sea from predators such as the [[leopard seal]]. Typically, penguins do not approach closer than about 3 meters (10 ft) at which point they become nervous. This is also the distance that Antarctic tourists are told to keep from penguins (tourists are not supposed to approach closer than 3 meters, but are not expected to withdraw if the penguins come closer).
==Penguin biology==
=== Anatomy ===
[[Image:Orcas and penguins.jpg|[[Orca]]s swim by an iceberg with [[Adélie]] penguins in the [[Ross Sea]], [[Antarctica]]. The [[Drygalski ice tongue]] is visible in the background.|thumb|250px]]
Penguins are superbly adapted to an aquatic life. Their [[wing]]s have become flippers, useless for flight in the air. In the water, however, penguins are astonishingly agile. Within the smooth [[plumage]] a layer of air is preserved, ensuring buoyancy. The air layer also helps insulate the birds in cold waters.
On land, penguins use their [[tail]]s and wings to maintain balance for their upright stance.
All penguins are [[countershading|countershaded]] for [[camouflage]] – that is, they have a white underside and a dark (mostly black) upperside. A predator looking up from below (such as an [[orca]] or a [[leopard seal]]) has difficulty distinguishing between a white penguin belly and the reflective water surface. The dark plumage on their backs camouflages them from above.
Diving penguins reach 6 to 12 km/h (3.7 to 7.5 mph), though there are reports of velocities of 27 km/h (17 mph) (which are more realistic in the case of startled flight). The small penguins do not usually dive deep; they catch their prey near the surface in dives that normally last only one or two minutes. Larger penguins can dive deep in case of need. Dives of the large Emperor Penguin have been recorded which reach a depth of 565 m (1,870 ft) and last up to 22 minutes.
Penguins either waddle on their feet or slide on their bellies across the snow, a movement called "tobogganing", which conserves energy while moving quickly. They also jump with both feet together if they want to move more quickly or cross steep or rocky terrain.
Penguins have an average sense of [[hearing (sense)|hearing]] for birds;<ref name="Wever">Wever ''et al.'' (1969).</ref> this is used by parents and chicks to locate one another in crowded [[seabird colony|colonies]].<ref name="Jouventin">Jouventin ''et al.'' (1999).</ref> Their [[eye]]s are adapted for underwater vision, and are their primary means of locating prey and avoiding predators; in air it has been suggested that they are [[nearsighted]], although research has not supported this hypothesis.<ref name="Sivak">Sivak ''et al.'' (1987).</ref>
Penguins have a thick layer of insulating feathers which serve to keep them warm in water (heat loss in water is much greater than in air). The Emperor penguin (the largest penguin) has the largest body mass of all penguins, which further reduces relative surface area and heat loss. They also are able to control blood flow to their extremities, reducing the amount of blood which gets cold, but still keeping the extremities from freezing. In the extreme cold of the Antarctic winter, the females are at sea fishing for food leaving the males to brave the weather by themselves. They often huddle together to keep warm and rotate positions to make sure that each penguin gets a turn in the center of the heat pack.
They can drink salt water because their [[supraorbital gland]] filters excess salt from the bloodstream.<ref>{{cite web | url=http://www.zoo.org/educate/fact_sheets/penguin/penguin.htm | title=Animal Fact Sheets | accessdate=2006-07-21}}</ref><ref>{{cite web | url=http://www.stlzoo.org/animals/abouttheanimals/birds/penguins/humboldtpenguin.htm | title=Humboldt Penguin :: Saint Louis Zoo | accessdate=2006-07-21}}</ref><ref>{{cite web | url=http://users.iafrica.com/b/bo/boulders/Vans%20book.htm | title=African Penguins and Penguins of the World | accessdate=2006-07-21}}</ref> The salt is excreted in a concentrated fluid from the nasal passages.
=== Breeding ===
[[Image:Pygoscelis antarctica trying to get to iceberg.wmv.OGG|200px|thumb|[[Chinstrap Penguin]]s in [[Antarctica]]]]
Penguins form monogamous pairs for a breeding season, though the rate the same pair recouples varies drastically. Most penguins lay two eggs in a clutch, though the two largest species, the Emperor and the [[King Penguin]]s, lay only one.<ref name=Will23>Williams ''(The Penguins)'' p. 23</ref> The parents cooperate in caring for the clutch and the young. During the cold season on the other hand the mates separate for several months to protect the egg. Usually, the male stays with the egg and keeps it warm while the female goes to sea to find food for the baby. When the female comes back, they switch roles.
Penguin eggs are smaller than any other bird species when compared proportionally to the weight of the parent birds; at 52 grams, the Little Penguin egg is 4.7% of its mothers' weight, and the 450-gram Emperor Penguin egg is 2.3%.<ref name=Will23/> The relatively thick shell forms between 10 and 16% of the weight of a penguin egg, presumably to minimise risk of breakage in an adverse nesting environment. The yolk, too, is large, and comprises 22–31% of the egg. Some yolk often remains when a chick is born, and is thought to help sustain it if parents are delayed in returning with food.<ref name=Will24>Williams ''(The Penguins)'' p. 24</ref>
When mothers lose a [[chick]], they sometimes attempt to "steal" another mother's chick, usually unsuccessfully as other females in the vicinity assist the defending mother in keeping her chick. In some species, such as [[Emperor Penguin]]s, young penguins assemble in large groups called [[crèche (zoology)|crèche]]s.
=== Isabelline penguins ===
[[Image:Isabelline Adelie.jpg|thumb|Isabelline Adélie penguin on Gourdin Island, December 2002]]
Perhaps one in 50,000 penguins (of most species) are born with brown rather than black plumage. These are called Isabelline penguins, possibly in reference to the legend that the archduchess [[Isabella of Austria]] vowed not to change her undergarments until her husband united the northern and southern Low Countries by taking the city of Ostend – which took three years to accomplish.<ref>[http://www.notornis.org.nz/free_issues/Notornis_50-2003/Notornis_50_1_43.pdf]<!-- needs a description --></ref> Isabellinism is different from albinism, though the faded color of the plumage calls albinism to mind. Isabelline penguins tend to live shorter lives than normal penguins, as they are not well-camouflaged against the deep, and are often passed over as mates.
==Systematics and evolution==
===Systematics===
Updated after Marples (1962), Acosta Hospitaleche (2004), and Ksepka ''et al.'' (2006). See the [[Penguin#Gallery of living species|gallery]] for images of most living species.
'''ORDER SPHENISCIFORMES'''
*'''[[Basal (phylogenetics)|Basal]] and unresolved taxa''' (all [[fossil]])
** ''[[Waimanu]]'' – basal (Middle-Late Paleocene)
** ''[[Perudyptes]]'' (Middle Eocene of Atacama Desert, Peru) – basal?
**Spheniscidae gen. et sp. indet. CADIC P 21 (Leticia Middle Eocene of Punta Torcida, Argentina: Clarke ''et al.'' 2003)
** ''[[Delphinornis]]'' (Middle/Late Eocene? – Early Oligocene of Seymour Island, Antarctica) – Palaeeudyptinae, basal, new subfamily 1?<!-- Cladistics22:412 -->
** ''[[Archaeospheniscus]]'' (Middle/Late Eocene – Late Oligocene) – Palaeeudyptinae? New subfamily 2?
** ''[[Marambiornis]]'' (Late Eocene –? Early Oligocene of Seymour Island, Antarctica) – Palaeeudyptinae, basal, new subfamily 1?<!-- Cladistics22:412 -->
** ''[[Mesetaornis]]'' (Late Eocene –? Early Oligocene of Seymour Island, Antarctica) – Palaeeudyptinae, basal, new subfamily 1?<!-- Cladistics22:412 -->
** ''[[Tonniornis]]'' (Late Eocene –? Early Oligocene of Seymour Island, Antarctica)
** ''[[Wimanornis]]'' (Late Eocene –? Early Oligocene of Seymour Island, Antarctica)
** ''[[Duntroonornis]]'' (Late Oligocene of Otago, New Zealand) – possibly Spheniscinae
** ''[[Korora (bird)|Korora]]'' (Late Oligocene of S Canterbury, New Zealand)
** ''[[Platydyptes]]'' (Late Oligocene of New Zealand) – possibly not monophyletic; Palaeeudyptinae, Paraptenodytinae or new subfamily?
** ''[[Spheniscus]] gen. et sp. indet (Late Oligocene/Early Miocene of Hakataramea, New Zealand)
** ''[[Madrynornis]]'' (Puerto Madryn Late Miocene of Argentina) – possibly Spheniscinae
** ''[[Pseudaptenodytes]]'' (Late Miocene/Early Pliocene)
** ''[[Dege (penguin)|Dege]]'' (Early Pliocene of South Africa) – possibly Spheniscinae<!-- Cladistics22:412 -->
** ''[[Marplesornis]]'' (Early Pliocene) – possibly Spheniscinae<!-- Cladistics22:412 -->
** ''[[Nucleornis]]'' (Early Pliocene of Duinfontain, South Africa) – possibly Spheniscinae<!-- Cladistics22:412 - lapsus "Nucleaornis" -->
** ''[[Inguza]]'' (Late Pliocene) – probably Spheniscinae; formerly ''Spheniscus predemersus''
* '''Family Spheniscidae'''
** '''Subfamily [[Palaeeudyptinae]]''' – Giant penguins ([[fossil]])
*** ''[[Crossvallia]]'' (Cross Valley Late Paleocene of Seymour Island, Antarctica) – tentatively assigned to this subfamily
*** ''[[Anthropornis]]'' (Middle Eocene? – Early Oligocene of Seymour Island, Antarctica) – tentatively assigned to this subfamily<!-- Cladistics22:412 -->
**** Nordenskjoeld's Giant Penguin, ''[[Anthropornis nordenskjoeldi]]''
*** ''[[Icadyptes]]'' (Late Eocene of Atacama Desert, Peru)
*** ''[[Palaeeudyptes]]'' (Middle/Late Eocene – Late Oligocene) – polyphyletic; some belong in other subfamilies
*** ''[[Pachydyptes]]'' (Late Eocene)
*** ''[[Anthropodyptes]]'' (Middle Miocene) – tentatively assigned to this subfamily
** '''Subfamily [[Paraptenodytinae]]''' – Stout-footed penguins ([[fossil]])<!-- American Museum novitates 2488: 1 -->
*** ''[[Arthrodytes]]'' (San Julian Late Eocene/Early Oligocene – Patagonia Early Miocene of Patagonia, Argentina)<!-- American Museum novitates 2488:1; Cladistics22:412 where lapsus "-dyptes" -->
*** ''[[Paraptenodytes]]'' (Early – Late Miocene/Early Pliocene)
** '''Subfamily [[Palaeospheniscinae]]''' – Slender-footed penguins ([[fossil]])
*** ''[[Eretiscus]]'' (Patagonia Early Miocene of Patagonia, Argentina)<!-- Cladistics22:412 -->
*** ''[[Palaeospheniscus]]'' (Early? – Late Miocene/Early Pliocene) – includes ''Chubutodyptes''
** '''Subfamily Spheniscinae''' – Modern penguins
*** ''[[Aptenodytes]]'' – Great penguins (2 species)
*** ''[[Pygoscelis]]'' – Brush-tailed penguins (3 species)
*** ''[[Eudyptula]]'' – Little penguins (1 or 2 species)
*** ''[[Spheniscus]]'' – Banded penguins (4 species)
*** ''[[Megadyptes]]'' – Yellow-eyed Penguin
*** ''[[Eudyptes]]'' – Crested penguins (6–8 living species)
'''Taxonomy''': Clarke ''et al.'' (2003) and Ksepka ''et al.'' (2006) apply the [[phylogenetic taxonomy|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 taxonomy|Linnean taxon]] ''Sphenisciformes'',<ref name="Clarke">Clarke ''et al.'' (2003).</ref> 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 seems spurious and in any case is confusing; the established Linnean system is thus followed here.
===Evolution===
The [[evolution]]ary history of penguins is well-researched and represents a showcase of evolutionary [[biogeography]]; though as penguin bones of any one species vary much in size and few good specimens are known, the [[alpha taxonomy]] of many prehistoric forms still leaves much to be desired. Some seminal articles about penguin prehistory have been published since 2005,<ref name="B&G">Bertelli & Giannini, (2005).</ref><ref name="Baker">Baker ''et al.'' (2006).</ref><ref name="Ksepka">Ksepka ''et al.'' (2006).</ref><ref name="Slack">Slack ''et al.'' (2006).</ref> the evolution of the living genera can be considered resolved by now.
The [[Basal (phylogenetics)|basal]] penguins lived around the time of the [[Cretaceous–Tertiary extinction event]] somewhere in the general area of (southern) [[New Zealand]] and [[Byrd Land]], Antarctica.<ref name="Ksepka"/> Due to [[plate tectonics]], these areas were at that time less than {{km to mi|1500}} apart rather than the {{km to mi|4000}} of today. The [[most recent common ancestor]] of penguins and their [[Cladistics|sister clade]] can be roughly dated to the [[Campanian]]–[[Maastrichtian]] boundary, around 70–68 mya.<ref name="Baker"/><ref name="Slack"/><ref>The exact divergence dates according to Baker ''et al.'' (2006) mentioned in this section are not as precisely resolved as it appears to be due to uncertainties of the [[molecular clock]] used.</ref>
What can be said as certainly as possible in the absence of direct (i.e., fossil) evidence is that by the end of the [[Cretaceous]], the penguin lineage must have been evolutionarily well distinct, though much less so [[morphology (biology)|morphologically]]; it is fairly likely that they were not yet entirely flightless at that time, as flightless birds have generally low resilience to the breakdown of [[trophic web]]s which follows the initial phase of mass extinctions because of their below-average dispersal capabilities (''see also'' [[Flightless Cormorant]]).
====The basal fossils====
The oldest known [[fossil]] penguin species is ''Waimanu manneringi'', which lived in the early [[Paleocene]] epoch of [[New Zealand]], or about 62 [[mya (unit)|mya]].<ref name="Slack"/> While they were not as well-adapted to aquatic life as modern penguins, ''[[Waimanu]]'' were generally [[loon]]-like birds but already 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, 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,<ref>
''Contra'' Baker ''et al.'' (2006).</ref>
primitive penguins had spread to [[South America]] and were in the process of expanding into [[Atlantic]] waters.<ref name="Clarke"/>
====Palaeëudyptines====
During the Late Eocene and the Early [[Oligocene]] (40–30 mya), some lineages of gigantic penguins existed. [[Nordenskjoeld's Giant Penguin]] was the tallest, growing nearly 1.80 meters (6 ft) tall. The [[New Zealand Giant Penguin]] was probably the heaviest, weighing 80 kg or more. Both were found on [[New Zealand]], the former also in the Antarctic farther eastwards.
Traditionally, most extinct species of penguins, giant or small, had been placed in the [[paraphyletic]] [[subfamily]] called [[Palaeeudyptinae]]. More recently, with new taxa being discovered and placed in the [[phylogeny]] if possible, it is becoming accepted that there were at least two major extinct lineages. One or two closely related ones occurred in [[Patagonia]], and at least one other – which is or includes the paleeudyptines as recognized today – occurred on most [[Antarctic]] and [[subantarctic]] coasts.
But size plasticity seems to have been great at this initial stage of penguin [[adaptive radiation|radiation]]: on [[Seymour Island]], Antarctica, for example, around 10 known species of penguins ranging in size from medium to huge apparently coexisted some 35 mya during the [[Priabonian]] (Late Eocene).<ref>Jadwiszczak, (2006).</ref> It is not even known whether the gigantic palaeeudyptines constitute a [[monophyletic]] lineage, or whether gigantism was evolved independently in a much restricted Palaeeudyptinae and the Anthropornithinae – whether they were considered valid, or whether there was a wide size range present in the Palaeeudyptinae as delimited as usually done these days (i.e., including ''[[Anthropornis nordenskjoeldi]]'').<ref name="Ksepka"/> The oldest well-described giant penguin, the 5-foot-tall ''[[Icadyptes salasi]]'', actually occurred as far north as northern [[Peru]] about 36 mya.
In any case, the gigantic penguins had disappeared by the end of the [[Paleogene]], around 25 mya. Their decline and disappearance coincided with the spread of the Squalodontoidea and other primitive, fish-eating [[toothed whale]]s, which certainly competed with them for food, and were ultimately more successful.<ref name="Baker"/> A new lineage, the [[Paraptenodytes]] which includes smaller but decidedly stout-legged forms, had already arisen in southernmost South America by that time. The early [[Neogene]] saw the emergence of yet another morphotype in the same area, the similarly-sized but more gracile [[Palaeospheniscinae]], as well as the radiation which gave rise to the penguin [[biodiversity]] of our time.
====Origin and systematics of modern penguins====
Modern penguins consititute two undisputed [[clade]]s and another two more basal genera with more ambiguous relationships.<ref name="B&G"/> The origin of the Spheniscinae lies probably in the latest Paleogene, and geographically it must have been much the same as the general area in which the order evolved: the oceans between the Australia-New Zealand region and the Antarctic.<ref name="Baker"/> Presumedly diverging from other penguins around 40 mya,<ref name="Baker"/> it seems that the Spheniscinae were for quite some time limited to their ancestral area, as the well-researched deposits of the [[Antarctic Peninsula]] and [[Patagonia]] have not yielded Paleogene fossils of the subfamily. Also, the earliest spheniscine lineages are those with the most southern distribution.
The genus ''[[Aptenodytes]]'' appears to be the basalmost divergence among living penguins; they have bright yellow-orange neck, breast, and bill patches; incubate by placing their eggs on their feet, and when they hatch the chicks are almost naked. This genus has a distribution centered on the Antarctic coasts and barely extends to some subantarctic islands today.
''[[Pygoscelis]]'' contains species with a fairly simple black-and-white head pattern; their distribution is intermediate, centered on Antarctic coasts but extending somewhat northwards from there. In external [[morphology (biology)|morphology]], these apparently still resemble the common ancestor of the Spheniscinae, as ''Aptenodytes''' [[autapomorph]]ies are in most cases fairly pronounced [[adaptation (biology)|adaptation]]s related to that genus' extreme [[habitat]] conditions. As the former genus, ''Pygoscelis'' seems to have diverged during the Bartonian,<ref>
In fact, it is fairly likely that during the Bartonian, there was a near-synchronous but [[allopatric]] split between the ancestors of ''Aptenodytes'', ''Pygoscelis'', and the common ancestor of all remaining genera [Baker ''et al.'' (2006)].</ref>
but the range expansion and radiation which led to the present-day diversity probably did not occur until much later; around the [[Burdigalian]] stage of the Early [[Miocene]], roughly 20–15 mya.<ref name="Baker"/>
The [[genus|genera]] ''[[Spheniscus]]'' and ''[[Eudyptula]]'' contain species with a mostly subantarctic distribution centered on [[South America]]; some, however, range quite far northwards. They all lack [[carotenoid]] coloration, and the former genus has a conspicuous banded head pattern; they are unique among living penguins by nesting in burrows. This group probably radiated eastwards with the [[Antarctic Circumpolar Current]] out of the ancestral range of modern penguins throughout the [[Chattian]] (Late Oligocene), starting approximately 28 mya.<ref name="Baker"/> While the two genera separated during this time, the present-day diversity is the result of a [[Pliocene]] radiation, taking place some 4–2 mya.<ref name="Baker"/>
The ''Megadyptes''–''Eudyptes'' clade occurs at similar [[latitude]]s (though not as far north as the [[Galapagos Penguin]]), has its highest diversity in the New Zealand region, and represent a westward dispersal. They are characterized by hairy yellow ornamental head feathers; their bills are at least partly red. These two genera diverged apparently in the Middle Miocene ([[Langhian]], roughly 15–14 mya), but again, the living species of ''Eudyptes'' are the product of a later radiation, stretching from about the late [[Tortonian]] (Late Miocene, 8 mya) to the end of the Pliocene.<ref name="Baker"/>
The geographical and temporal pattern or spheniscine evolution corresponds closely to two episodes of [[global cooling]] documented in the [[paleoclimatology|paleoclimatic record]].<ref name="Baker"> The emergence of the subantarctic lineage at the end of the Bartonian corresponds with the onset of the slow period of cooling that eventually led to the [[ice age]]s some 35 million years later. With habitat on the Antarctic coasts declining, by the Priabonian more hospitable conditions for most penguins existed in the subantarctic regions rather than in Antarctica itself. Notably, the cold Antarctic Circumpolar Current also started as a continuous circumpolar flow only around 30 mya, on the one hand forcing the Antarctic cooling, and on the other facilitating the eastward expansion of ''[[Spheniscus]]'' to South America and eventually beyond.<ref name="Baker">
Later, an interspersed period of slight warming was ended by the [[Middle Miocene Climate Transition]], a sharp drop in global average temperature from 14–12 mya, and similar abrupt cooling events followed at 8 mya and 4 mya; by the end of the Tortonian, the [[Antarctic ice sheet]] was already much like today in volume and extent. The emergence of most of today's subantarctic penguin species almost certainly was caused by this sequence of Neogene climate shifts.
====Relationship to other bird orders====
Penguin ancestry beyond ''[[Waimanu]]'' remains unknown and not well-resolved by molecular or morphological analyses. The latter tend to be confounded by the strong adaptive autapomorphies of the Sphenisciformes; a sometimes perceived fairly close relationship between penguins and [[grebe]]s is almost certainly an error based on both groups' strong diving adaptations, which are [[homoplasies]]. On the other hand, different [[DNA sequence]] datasets do not agree in detail with each other either.
[[Image:Penguin at zoo.jpg|thumb|left|The penguin is an accomplished swimmer, having flippers instead of wings.]]
What seems clear is that penguins belong to a clade of Neoaves (living birds except [[paleognath]]s and [[fowl]]) which comprises what is sometimes called "higher waterbirds" to distinguish them from the more ancient [[waterfowl]]. This group contains such birds as [[stork]]s, [[Rallidae|rail]]s, and the [[seabird]]s, with the possible exception of the [[Charadriiformes]].<ref>Fain & Houde, (2004).</ref>
Inside this group, penguin relationships are far less clear. Depending on the analysis and dataset, a close relationship to [[Ciconiiformes]]<ref name="Slack"/> or to [[Procellariiformes]]<ref name="Baker"/> has been suggested. Some think the penguin-like [[Plotopteridae|plotopterids]] (usually considered relatives of [[anhinga]]s and [[cormorant]]s) may actually be a sister group of the penguins, and that penguins may have ultimately shared a common ancestor with the [[Pelecaniformes]] and consequently would have to be included in that order, or that the plotopterids were not as close to other pelecaniforms as generally assumed, which would necessitate splitting the traditional Pelecaniformes in three.<ref>Mayr, (2005).</ref><!-- presumed this ref covers the entire statement -->
The [[Auk]] of the [[Northern Hemisphere]] is superficially similar to penguins: they are not related to the penguins at all, but considered by some to be a product of moderate [[convergent evolution]].<ref>[http://evo.bio.psu.edu/hedgeslab/Publications/PDF-files/128.pdf Convergence and divergence in the evolution of aquatic birds] by Marcel Van Tuinen, Dave Brian Butvill, John A. W. Kirsch and S. Blair Hedges</ref>
== Penguins and humans ==
===Etymology===
The word ''Penguin'' is thought by some to derive from the [[Welsh language|Welsh]] words ''pen'' (head) and ''gwyn'' (white),<ref name = "OED">[http://dictionary.oed.com/cgi/entry/50174529?query_type=word&queryword=penguin&first=1&max_to_show=10&sort_type=alpha&result_place=1&search_id=e9qK-031OnY-14734&hilite=50174529 Oxford English Dictionary]. Accessed [[2007-03-21]].</ref> applied to the [[Great Auk]] which had white spots in front of its eyes (although its head was black); or from an island off Newfoundland known as ''Pengwyn'', due to its having a large white rock. (In the latter case, the name may also have come from [[Breton language|Breton]].) This theory is supported by the fact that penguins look remarkably like Great Auks in general shape.
It is also possible that ''penguin'' comes from the [[Latin]] ''pinguis'', “fat”. This is supported by the fact that the corresponding words in most other languages (e.g., French ''pingouin'', German ''Pinguin'') have ''i'' instead of ''e'' as the first vowel.<ref name="OED"/> However, a Welsh ''i'' is often sound-shifted to an ''e'' in the English language.{{Fact|date=March 2007}}
Another theory states that the word is an alteration of “pen-wing”, with reference to the rudimentary wings of both Great Auks and penguins, but there is no evidence to support this.<ref name="OED"/>
What may be a King Penguin but certainly is a member of the [[Spheniscidae]] appears on a 1599 map at the [[Strait of Magellan]] with the caption "Pinguyn". The map's features are labeled in Latin, such as ''Fretum Magellanicum'' ("Strait of Magellan"). In addition, there is ample evidence that the Latin term ''anser magellanicus'' ("Goose of Magellan" or "Magellanic Goose") was the usual term for penguins in the scholarly literature of that time. If the English word was derived from Latin – e.g. ''avis pinguis'' ("fat bird") or ''pinguinus'' ("the fat one"{{Verify source|date=February 2008}}) – it must have originated considerably earlier than 1600.
In a final twist to the story, the term "Magellanic Goose" (today usually "[[Magellan Goose]]") in our time has come to denote an actual [[Anseriformes|anseriform]], namely a ''[[Chloephaga]]'' sheldgoose.
The pronunciation of the word in English varies somewhat: as either "PEN-guin" or "PENG-guin".
=== Penguins in popular culture ===
[[Image:Tux.svg|100px|thumb|[[Tux]] the [[Linux kernel]] mascot]]
{{main|Penguins in popular culture}}
Penguins are popular around the world, primarily for their unusually upright, waddling gait and (compared to other birds) lack of fear of humans. Their striking black-and-white plumage is often likened to a [[black tie|tuxedo]] suit. <!-- Perhaps in reaction to this cutesy stereotype, fictional penguins are occasionally presented as grouchy or even sinister. [has been fact-tagged for months, completely unsubstantiated-->Mistakenly, some artists and writers have penguins based at the [[North Pole]]. This is incorrect, as there are almost no wild penguins in the [[northern hemisphere]], except the small group on the northernmost of the [[Galápagos]].
Penguins have been the subject of many books and films such as ''[[Happy Feet]]'' and ''[[Surf's Up (film)|Surf's Up]]'', both [[CGI]] films; ''[[March of the Penguins]]'', a documentary based on the migration process of Emperors; and a parody entitled ''[[Farce of the Penguins]]''. Penguins have also found their way into a number of cartoons and television dramas; perhaps the most notable of these is ''[[Pingu]]'', created by [[Silvio Mazzola]] in 1986 and covering more than 100 short episodes.
The tendency of penguins to form large groups feeds the stereotype that they all look exactly alike, a popular notion exploited by cartoonists such as [[Gary Larson]].
In the mid-2000s, penguins became one of the most publicized species of animals that formed lasting [[Homosexuality in animals#Penguins|homosexual]] couples. ''See [[And Tango Makes Three]].''
==Species photographs==
Photographs of the adults of living species are show:
<gallery caption = "[[Aptenodytes]], Great penguins (2 species)">
Image:Emperor Penguin Manchot empereur.jpg|[[Emperor Penguin]]s<br>''Aptenodytes forsteri''
Image:Penguins Edinburgh Zoo 2004 SMC.jpg|[[King Penguin]]s<br>''Aptenodytes patagonicus''
</gallery>
<gallery caption = "[[Pygoscelis]], Brush-tailed penguins (3 species)">
Image:Manchot 04.jpg|[[Chinstrap Penguin]]<br>''Pygoscelis antarctica''
Image:Pygoscelis_papua.jpg|[[Gentoo Penguin]]<br>''Pygoscelis papua''
Image:Adelie Penguin.jpg|[[Adelie Penguin]]<br>''Pygoscelis adeliae''
</gallery>
<gallery caption = "[[Eudyptula]], Little penguins (1 or 2 species)">
Image:Little Blue Penguin (Eudyptula minor) -Adelaide Zoo.jpg|[[Little Penguin]] or Fairy Penguin<br>''Eudyptula minor''
Image:White-flippered Penguin -standing on rocks.jpg|[[White-flippered Penguin]]<br>Eudyptula albosignata
</gallery>
<gallery caption = "[[Spheniscus]], Banded penguins (4 species)">
Image:penguin.jackass.arp.500pix.jpg|[[African Penguin]] or Jackass Penguin<br/>''Spheniscus demersus''
Image:Galapagos penguin (Spheniscus mendiculus) -Isabela2.jpg|[[Galapagos Penguin]]s<br/>''Spheniscus mendiculus''
Image:Humboldt Penguin.jpg|[[Humboldt Penguin]]<br>''Spheniscus humboldti''
Image:Magellanic-penguin02.jpg|[[Magellanic Penguin]]<br>''Spheniscus magellanicus''
</gallery>
<gallery caption ="[[Megadyptes]], Yellow-eyed Penguin">
Image:Yellow-eyed Penguin MC.jpg|[[Yellow-eyed Penguin]]<br>''Megadyptes antipodes''
</gallery>
<gallery caption ="[[Eudyptes]], Crested penguins (6–8 living species)">
Image:RoyalPenguins2.JPG|[[Royal Penguin]]<br>''Eudyptes schlegeli''
Image:Eudyptes chrysocome.jpg|[[Southern Rockhopper Penguin]]<br>''Eudyptes chrysocome''
Image:Fiordland penguin (Mattern).jpg|[[Fiordland Penguin]]<br>''Eudyptes pachyrhynchus''
Image:SnaresPenguin (Mattern).jpg|[[Snares Penguin]]<br>''Eudyptes robustus''
Image:Macaroni_penguin.jpg|[[Macaroni Penguin]]<br>''Eudyptes chrysolophus''
</gallery>
==General gallery==
<gallery>
Image:Eudyptes chrysolophus at south georgia.jpg|[[Macaroni penguin]] at South Georgia Island
Image:Pygoscelis antarctica feeding a chick.jpg.jpg|[[Chinstrap Penguin]] feeding a chick in [[Antarctica]]
Image:Adelie chicks in antarctica and Ms Explorer.jpg|Adélie chicks in Antarctica
Image:Seal and king penguins.jpg|[[Southern Elephant Seal]] and [[King Penguin]]s
</gallery>
== References ==
=== Footnotes ===
{{reflist|2}}
=== Bibliography ===
{{refbegin}}
* [http://news.nationalgeographic.com/news/2007/06/070625-giant-penguins.html Two new fossil penguin species found in Peru]
* '''Acosta Hospitaleche''', Carolina (2004): ''Los pingüinos (Aves, Sphenisciformes) fósiles de Patagonia. Sistemática, biogeografía y evolución''. Doctoral thesis, Department of Natural Sciences and Museum, Universidad Nacional de La Plata. La Plata, Argentina. [in Spanish] [http://www.sedici.unlp.edu.ar/search/request.php?id_document=ARG-UNLP-TPG-0000000084&request=request PDF fulltext]
* '''Baker''', Allan J.; Pereira, Sergio Luiz; Haddrath, Oliver P. & Edge, Kerri-Anne (2006): Multiple gene evidence for expansion of extant penguins out of Antarctica due to global cooling. ''[[Proceedings of the Royal Society#Proceedings of the Royal Society B|Proc. R. Soc. B]]'' '''273''': 11-17. <small>{{doi|10.1098/rspb.2005.3260}}</small> [http://www.journals.royalsoc.ac.uk/content/pm36848701v24640/fulltext.pdf PDF fulltext]
* '''Banks''', Jonathan C.; Mitchell, Anthony D.; Waas, Joseph R. & Paterson, Adrian M. (2002): An unexpected pattern of molecular divergence within the blue penguin (''Eudyptula minor'') complex. ''Notornis'' '''49'''(1): 29–38. [http://www.notornis.org.nz/free_issues/Notornis_49-2002/Notornis_49_1_29.pdf PDF fulltext]
* '''Bertelli''', Sara & '''Giannini''', Norberto P. (2005): A phylogeny of extant penguins (Aves: Sphenisciformes) combining morphology and mitochondrial sequences. ''Cladistics'' '''21'''(3): 209–239. <small>{{doi|10.1111/j.1096-0031.2005.00065.x}}</small> (HTML abstract)
* '''Clarke''', Julia A.; Olivero, Eduardo B. & Puerta, Pablo (2003): Description of the earliest fossil penguin from South America and first Paleogene vertebrate locality of Tierra Del Fuego, Argentina. ''American Museum novitates'' '''3423''': 1-18. [http://digitallibrary.amnh.org/dspace/bitstream/2246/2788/1/N3423.pdf PDF fulltext]
* '''Davis'''; Lloyd S. & '''Renner'''; M. (1995). ''Penguins'' . London: T & A D Poyser. <small>ISBN 0-7136-6550-5</small>
* '''Fain''', Matthew G. & '''Houde''', Peter (2004): Parallel radiations in the primary clades of birds. ''[[Evolution (journal)|Evolution]]'' '''58'''(11): 2558-2573. <small>{{DOI|10.1554/04-235}}</small> [http://biology-web.nmsu.edu/houde/Parallel_radiations.pdf PDF fulltext]
* '''Jadwiszczak''', Piotr (2006): Eocene penguins of Seymour Island, Antarctica: taxonomy. ''Polish Polar Research'' '''27'''(1), 3–62. [http://www.polish.polar.pan.pl/ppr27/ppr27-003.pdf PDF fulltext]
* '''Jouventin''', P; Aubin, T. & T Lengagne (1999) "Finding a parent in a king penguin colony: the acoustic system of individual recognition" ''Animal Behaviour'' '''57''': 1175–1183 [http://www.cb.u-psud.fr/animbehavkp.pdf]
* '''Ksepka''', Daniel T., Bertelli, Sara & Giannini, Norberto P. (2006): The phylogeny of the living and fossil Sphenisciformes (penguins). ''Cladistics'' '''22'''(5): 412–441. <small>{{doi|10.1111/j.1096-0031.2006.00116.x}}</small> (HTML abstract)
* '''Marples''', B. J. (1962): Observations on the history of penguins. ''In:'' Leeper, G. W. (ed.), ''The evolution of living organisms''. Melbourne, Melbourne University Press: 408-416.
* '''Mayr''', G. (2005): Tertiary plotopterids (Aves, Plotopteridae) and a novel hypothesis on the phylogenetic relationships of penguins (Spheniscidae). ''Journal of Zoological Systematics and Evolutionary Research'' '''43'''(1): 61-71. <small>{{doi|10.1111/j.1439-0469.2004.00291.x}}</small> [http://www.senckenberg.de/files/content/forschung/abteilung/terrzool/ornithologie/plotopteridae.pdf PDF fulltext]
* '''Sivak''', J.; Howland, H. & McGill-Harelstad, P. (1987) "Vision of the Humboldt Penguin (Spheniscus humboldti) in Air and Water " ''Proceedings of the Royal Society of London. Series B, Biological Sciences''. '''229'''(1257): 467-472
* '''Slack''', Kerryn E.; Jones, Craig M.; Ando, Tatsuro; Harrison G. L. "Abby"; Fordyce R. Ewan; Arnason, Ulfur & Penny, David (2006): Early Penguin Fossils, plus Mitochondrial Genomes, Calibrate Avian Evolution. ''Molecular Biology and Evolution'' '''23'''(6): 1144-1155. <small>{{DOI|10.1093/molbev/msj124}}</small> [http://mbe.oxfordjournals.org/cgi/reprint/23/6/1144 PDF fulltext] [http://mbe.oxfordjournals.org/cgi/content/full/msj124/DC1 Supplementary Material]
*'''Wever''', E.; Herman, P.; Simmons, J. & Hertzler D (1969) "Hearing in the Blackfooted Penguin, Spheniscus demersus, as Represented by the Cochlear Potentials" ''PNAS'' '''63'''(3): 676-680 [http://www.pnas.org/cgi/reprint/63/3/676]
* '''Williams'''; Tony D. (1995). ''The Penguins - Spheniscidae'' . Oxford: Oxford University Press. <small>ISBN 0-19-854667-X</small>
{{refend}}
== External links ==
* [http://www.penguinworld.com Penguin World]
* [http://www.penguinpage.net penguinpage.net - Penguin research projects on the web]
* [http://www.70south.com/resources/antarctic-animals/antarctic-penguins Penguin information on 70South]
* [http://www.pinguins.info Information about penguins at pinguins.info]
* [http://www.pbs.org/wnet/nature/penguins/index.html PBS Nature: The World of Penguins]
* [http://www.itis.usda.gov Integrated Taxonomic Information System]
* [http://www.seaworld.org/infobooks/Penguins/home.html Seaworld Penguin Information]
* [http://ibc.hbw.com/ibc/phtml/familia.phtml?idFamilia=7 Penguin Videos] on the Internet Bird Collection
{{Footer Birds}}
[[Category:Antarctic birds]]
[[Category:Flightless birds]]
[[Category:Penguins|*]]
[[Category:Seabirds]]
[[Category:Spheniscidae|*]]
[[Category:Spheniscinae|*]]
[[Category:Sphenisciformes|*]]
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[[af:Pikkewyn]]
[[ar:بطريق]]
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[[ca:Pingüí]]
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[[lv:Pingvīnu dzimta]]
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[[nl:Pinguïns]]
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[[ta:பென்குயின்]]
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[[tr:Penguen]]
[[uk:Пінгвіни]]
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