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===Evolution===
The ]ary history of penguins is well-researched and represents a showcase of evolutionary ]; though as penguin bones of any one species vary much in size and few good specimens are known, the ] of many prehistoric forms still leaves much to be desired. Some seminal articles about penguin prehistory have been published since 2005 (Bertelli & Giannini 2005, Baker ''et al.'' 2006, Ksepka ''et al.'' 2006, Slack ''et al.'' 2006), the evolution of the living genera can be considered resolved by now.


According to the comprehensive review of the available evidence by Ksepka ''et al.'' (2006), the ] penguins lived around the time of the ] somewhere in the general area of (southern) ] and ], Antarctica. Due to ], these areas were at that time less than {{km to mi|1500}} apart rather than the {{km to mi|4000}} of today. The ] of penguins and their ] can be roughly dated to the ]-] boundary, around 70-68 mya (Baker ''et al.'' 2006, Slack ''et al.'' 2006)<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 ] 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 ], the penguin lineage must have been evolutionarily well distinct, though much less so ]; 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 ]s which follows the initial phase of mass extinctions because of their below-average dispersal capabilities (''see also'' ]).

====The basal fossils====
The oldest known ] penguin species is ''Waimanu manneringi'', which lived in the early ] epoch of ], or about 62 ] (Slack ''et al.'' 2006). While they were not as well adapted to aquatic life as modern penguins, '']'' were generally ]-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 ] proves that by the ] (Middle ]), some 39-38 mya<ref>
''Contra'' Baker ''et al.'' (2006).</ref>,
primitive penguins had spread to ] and were in the process of expanding into ] waters (Clarke ''et al''. 2003).

====Palaeëudyptines====
During the Late Eocene and the Early ] (40-30 mya), some lineages of gigantic penguins existed. ] was the tallest, growing nearly 1.80 meters (6 ft) tall. The ] was probably the heaviest, weighing 80 kg or more. Both were found on ], the former also in the Antarctic farther eastwards.
Traditionally, most extinct species of penguins, giant or small, had been placed in the ] ] called ]. More recently, with new taxa being discovered and placed in the ] if possible, it is becoming accepted that there were at least 2 major extinct lineages. One or two closely related ones occurred in ], and at least one other - which is or includes the paleeeudyptines as recognized today - occurred on most ] and ] coasts.

But size plasticity seems to have been great at this initial stage of penguin ]: on ], Antarctica, for example, around ten known species of penguins ranging from medium to huge size apparently coexisted some 35 mya during the ] (Late Eocene) (Jadwiszczak 2006). It is not even known whether the gigantic palaeeudyptines constitute a ] lineage, or whether gigantism was evolved independently in a much restricted Palaeeudyptinae and the Anthropornithinae - were they considered valid -, or whether there was a wide size range present in the Palaeeudyptinae as delimited as usually done these days (i.e., including '']'') (Ksepka ''et al.'' 2006). The oldest well-described giant penguin, the 5-foot-tall '']'', actually occurred as far north as northern ] about 36 ].

In any case, the gigantic penguins had disappeared by the end of the ], around 25 mya. Interestingly, their decline and disappearance coincides with the spread of the Squalodontoidea and other primitive, fish-eating ]s, which certainly competed with them for food, and were ultimately more successful (Baker ''et al.'' 2006). A new lineage, the ] which includes smaller but decidedly stout-legged forms, had already arisen in southernmost South America by that time. The early ] saw the emergence of yet another morphotype in the same area, the similarly-sized but more gracile ], as well as the radiation which gave rise to the penguin ] of our time.

====Origin and systematics of modern penguins====
Modern penguins consititute two undisputed ]s and another two more basal genera with more ambiguous relationships (Bertelli & Giannini 2005). 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 (Baker ''et al.'' 2006). Presumedly diverging from other penguins around 40 mya (Baker ''et al.'' 2006), it seems that the Spheniscinae were for quite some time limited to their ancestral area, as the well-researched deposits of the ] and ] have not yielded Paleogene fossils of the subfamily. Also, the earliest spheniscine lineages are those with the most southern distribution.

The genus '']'' 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, they are almost naked. This genus has a distribution centered on the Antarctic coasts and barely extends to some subantarctic islands today.

'']'' 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 ], these apparently still resemble the common ancestor of the Spheniscinae, as ''Aptenodytes''' ]ies are in most cases fairly pronounced ]s related to that genus' extreme ] 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 ] 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 lead to the present-day diversity probably did not occur until much later, around the ] stage of the Early ], roughly 20-15 mya (Baker ''et al.'' 2006).

The ] '']'' and '']'' contain species with a mostly subantarctic distribution centered on ]; some, however, range quite far northwards. They all lack ] coloration, and the former genus has a conspicuous banded head pattern; they are unique among living penguins in nesting in burrows. This group probably radiated eastwards with the ] out of the ancestral range of modern penguins throughout the ] (Late Oligocene), starting approximately 28 mya (Baker ''et al.'' 2006). While the two genera separated during this time, the present-day diversity is the result of a ] radiation, taking place some 4-2 mya (Baker ''et al.'' 2006).

The ''Megadyptes'' - ''Eudyptes'' clade occurs at similar ]s (though not as far north as the ]), 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 (], roughly 15-14 mya), but again, the living species of ''Eudyptes'' are the product of a later radiation, stretching from about the late ] (Late Miocene, 8 mya) to the end of the Pliocene (Baker ''et al.'' 2006).

It is most interesting to note that the geographical and temporal pattern or spheniscine evolution corresponds closely to two episodes of ] documented in the ] (Baker ''et al.'' 2006). 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 ]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 '']'' to South America and eventually beyond (Baker ''et al.'' 2006).

Later, an interspersed period of slight warming was ended by the ], a sharp drop in global average temperature from 14 to 12 mya, and similar abrupt cooling events followed at 8 mya and 4 mya; by the end of the Tortonian, the ] 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 '']'' 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 ]s is almost certainly an error based on both groups' strong diving adaptations, which are ]. On the other hand, different ] datasets do not agree in detail with each other either.

What seems clear is that penguins belong to a clade of Neoaves (living birds except ]s and ]) which comprises what is sometimes called "higher waterbirds" to distinguish them from the more ancient ]. This group contains such birds as ]s, ]s, and the ]s, with the possible exception of the ] (Fain & Houde 2004).

Inside this group, penguin relationships are far less clear. Depending on the analysis and dataset, a close relationship to ] (e.g. Slack ''et al.'' 2006) or to ] (Baker ''et al.'' 2006) has been suggested. Some (e.g. Mayr 2005) think the penguin-like ] (usually considered relatives of ]s and ]s) may actually be a sister group of the penguins, and that penguins may have ultimately shared a common ancestor with the ] 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.

The ] of the ] is superficially similar to penguins, they are not related to the penguins at all, but considered by some to be a product of moderate ] <ref> by Marcel Van Tuinen, Dave Brian Butvill, John A. W. Kirsch and S. Blair Hedges</ref>


== Penguins and humans == == Penguins and humans ==

Revision as of 13:47, 18 December 2007

For other uses, see Penguin (disambiguation).

Penguins
Temporal range: Paleocene-Recent
Gentoo Penguin, Pygoscelis papua
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Sphenisciformes
Sharpe, 1891
Family: Spheniscidae
Bonaparte, 1831
Modern genera
A penguin encounters a human during Antarctic summer.

Penguins (order Sphenisciformes, family Spheniscidae) are a group of aquatic, flightless birds 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 (e.g. Williams, 1995; Davis & Renner, 2003); the actual situation seems to be more complicated (Banks et al. 2002). 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 penguins (Davis & Renner, 2003). 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 ten species live in the temperate zone; one lives as far north as the Galápagos Islands: the Galápagos Penguin.

The largest living species is the Emperor Penguin (Aptenodytes forsteri): adults average about 1.1 m (3 ft 7 in) tall and weigh 35 kg (75 lb) or more. The smallest penguin species is the 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 2000 km south of the Equator 35 mya, in a climate decidedy 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 (9 ft); they become nervous at about that distance. 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).

Penguins Are now an official extinct species in the wild. The only ones left are the ones in the zoos. This is all on your shoulders you people that drive big SUVs, and need a new can of hairspray every other hour. 

                       The late Save The Penguin Society



Systematics and evolution

Penguins and humans

Etymology

The word Penguin is thought by some to derive from the Welsh words pen (head) and gwyn (white), 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 a large white rock. (In the latter case, the name may also have come from 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. However, a Welsh 'i' is often sound-shifted to an 'e' in the English language,.

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 for this.

Penguins in popular culture

Tux the Linux kernel mascot
Main article: Penguins in popular culture

Penguins are popular around the world, primarily for their unusually upright, waddling pace and (compared to other birds) lack of fear of humans. Their striking black and white plumage is often likened to a tuxedo suit. Perhaps in reaction to this cutesy stereotype, fictional penguins are occasionally presented as grouchy or even sinister. Penguins have also been the subject of many books and documentary films such as Happy Feet and Surf's Up, both CGI-Animated Animal Adventure Films, March of the Penguins, a documentary based on the migration process of Emperors, and a parody film entitled Farce of the Penguins. Mistakenly, some artists and writers have penguins based in the North Pole. This is incorrect as there are almost no wild penguins in the northern hemisphere, and those only barely (northernmost of the Galápagos). 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.

Gallery of living species

References

  • 2 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. 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. 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. doi:10.1111/j.1096-0031.2005.00065.x (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. PDF fulltext
  • Davis; Lloyd S. & Renner; M. (1995). Penguins . London: T & A D Poyser. ISBN 0-7136-6550-5
  • Jadwiszczak, Piotr (2006): Eocene penguins of Seymour Island, Antarctica: taxonomy. Polish Polar Research 27(1), 3–62. 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
  • Ksepka, Daniel T., Bertelli, Sara & Giannini, Norberto P. (2006): The phylogeny of the living and fossil Sphenisciformes (penguins). Cladistics 22(5): 412–441. doi:10.1111/j.1096-0031.2006.00116.x (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. doi:10.1111/j.1439-0469.2004.00291.x 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. doi:10.1093/molbev/msj124 PDF fulltext 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
  • Williams; Tony D. (1995). The Penguins - Spheniscidae . Oxford: Oxford University Press. ISBN 0-19-854667-X

Footnotes

  1. ^ Oxford English Dictionary. Accessed 2007-03-21.

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