Editing Penguin (section)

====Origin and systematics of modern penguins====
Modern penguins constitute two undisputed [[clade]]s and another two more basal genera with more ambiguous relationships.<ref name="B&G"/> To help resolve the evolution of this [[Order (biology)|order]], 19 high-coverage genomes that, together with two previously published genomes, encompass all extant penguin species have been sequenced.<ref>{{Cite journal |last1=Pan |first1=Hailin |last2=Cole |first2=Theresa L. |last3=Bi |first3=Xupeng |last4=Fang |first4=Miaoquan |last5=Zhou |first5=Chengran |last6=Yang |first6=Zhengtao |last7=Ksepka |first7=Daniel T. |last8=Hart |first8=Tom |last9=Bouzat |first9=Juan L. |last10=Argilla |first10=Lisa S. |author-link10=Lisa Argilla |last11=Bertelsen |first11=Mads F. |date=September 1, 2019 |title=High-coverage genomes to elucidate the evolution of penguins |url= |journal=GigaScience |language=en |volume=8 |issue=9 |doi=10.1093/gigascience/giz117 |pmc=6904868 |pmid=31531675}}</ref> 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"/> Presumably 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.<ref name="Ksepka">{{cite journal |doi=10.1111/j.1096-0031.2006.00116.x |last1=Ksepka |first1=D. T. |last2=Bertelli |first2=S. |last3=Giannini |first3=N. P. |title=The phylogeny of the living and fossil Sphenisciformes (penguins) |journal=Cladistics |volume=22 |year=2006 |pages=412–441 |issue=#5 |s2cid=85673628 |doi-access=free }}</ref><ref name=CB08>{{cite book |title=Systematics and Taxonomy of Australian Birds|vauthors=Christidis L, Boles WE |year=2008 |publisher=CSIRO Publishing |location=Canberra |isbn=978-0-643-06511-6 |page=97}}</ref> 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 centred 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, centred 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)|adaptations]] related to that genus' extreme [[habitat]] conditions. As the former genus, ''Pygoscelis'' seems to have diverged during the Bartonian,<ref>
It is 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|Baker]]).</ref> but the range expansion and radiation that 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 centred on [[South America]]; some, however, range quite far northwards. They all lack [[carotenoid]] colouration 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 [[Galápagos penguin]]), has its highest diversity in the New Zealand region, and represents 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), although 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"/>