Editing Pinniped (section)

==Taxonomy==
{{Further|List of pinnipeds}}
{{Cladogram|align=right|title=
|clade=
{{clade|style=font-size:75%;line-height:75%;width:500px;
 |label1='''[[Pinnipedia]]'''
 |1={{clade
  |label1=[[Otarioidea]]
  |1={{clade
   |label1=[[Odobenidae]]
   |1=[[Walrus]]<!-- Odobenus rosmarus -->
   |label2=[[Otariidae]]
   |sublabel2=(eared seals)
   |2={{clade
    |1=[[Northern fur seal]]<!-- Callorhinus ursinus -->
    |2={{clade
     |1={{clade
      |1=[[Steller sea lion]]<!-- Eumetopias jubatus -->
      |2={{clade
       |1=[[Galápagos sea lion]]<!-- Zalophus wollebaeki -->
       |2=[[California sea lion]]<!-- Zalophus californianus -->
       }}
      }}
     |2={{clade
      |1=[[South American sea lion]]<!-- Otaria flavescens (= O. byronia) -->
      |2={{clade
       |1={{clade
        |1=[[New Zealand sea lion]]<!-- Phocarctos hookeri -->
        |2=[[Australian sea lion]]<!-- Neophoca cinerea -->
        }}
       |2={{clade <!-- Arctocephalus -->
        |1={{clade
         |1=[[Subantarctic fur seal]]<!-- Arctocephalus tropicalis -->
         |2=[[Brown fur seal]]<!-- Arctocephalus pusillus -->
         }}
        |2={{clade
         |1={{clade
          |1=[[Guadalupe fur seal]]<!-- Arctocephalus townsendi -->
          |2=[[Juan Fernández fur seal]]<!-- Arctocephalus philippii -->
          }}
         |2={{clade
          |1=[[Antarctic fur seal]]<!-- Arctocephalus gazella -->
          |2={{clade
           |1=[[Arctocephalus forsteri|Antipodean fur seal]]<!--Arctocephalus forsteri-->
           |2={{clade
            |1=[[Galápagos fur seal]]<!-- Arctocephalus galapagoensis -->
            |2=[[South American fur seal]]<!--Arctocephalus australis-->
            }}
           }}
          }}
         }}
        }}
       }}
      }}
     }}
    }}
   }}
  |label2=[[Phocidae]]
  |sublabel2=(earless seals)
  |2={{clade
   |label1=[[Phocinae]]
   |1={{clade
    |1=[[Bearded seal]]<!-- Erignathus barbatus -->
    |2={{clade
     |1=[[Hooded seal]]<!-- Cystophora cristata -->
     |2={{clade
      |1={{clade
       |1={{clade
        |1=[[Harp seal]]<!-- Pagophilus groenlandicus -->
        |2=[[Ribbon seal]]<!-- Histriophoca fasciata) -->
        }}
       |2={{clade
        |1={{clade
         |1=[[Harbor seal]]<!-- Phoca vitulina -->
         |2=[[Spotted seal]]<!-- Phoca largha -->
         }}
        |2={{clade
         |1=[[Grey seal]]<!-- Halichoerus grypus-->
         |2={{clade
          |1=[[Baikal seal]]<!-- Pusa sibirica -->
          |2={{clade
           |1=[[Ringed seal]]<!-- Pusa hispida -->
           |2=[[Caspian seal]]<!-- Pusa caspica -->
           }}
          }}
         }}
        }}
       }}
      }}
     }}
    }}
   |label2=[[Monachinae]]
   |2={{clade
    |1={{clade
     |label1=[[Miroungini]]
     |sublabel1=(elephant seals)
     |1={{clade
      |1=[[Southern elephant seal]]<!-- Mirounga leonina -->
      |2=[[Northern elephant seal]]<!-- Mirounga angustirostris -->
      }}
     |label2=[[Lobodontini]]
     |2={{clade
      |1={{clade
       |1=[[Ross seal]]<!-- Ommatophoca rossii -->
       |2=[[Crabeater seal]]<!-- Lobodon carcinophaga -->
       }}
      |2={{clade
       |1=[[Weddell seal]]<!-- Leptonychotes weddellii -->
       |2=[[Leopard seal]]<!-- Hydrurga leptonyx-->
       }}
      }}
     }}
    |label2=[[Monachini]]
    |sublabel2=(monk seals)
    |2={{clade
     |1=[[Hawaiian monk seal]]<!-- Neomonachus schauinslandi -->
     |2=[[Mediterranean monk seal]]<!-- Monachus monachus -->
     }}
    }}
   }}
  }}
 }}
|caption=[[Cladogram]] of [[extant taxon|extant]] pinnipeds based on molecular evidence by Park et al., 2024.<ref name=Park2024>{{cite journal |last1=Park |first1=T. |last2=Burin |first2=G. |last3=Lazo-Cancino |first3=D. |last4=Rees |first4=J. P. G. |last5=Rule |first5=J. P. |last6=Slater |first6=G. J. |last7=Cooper |first7=N. |year=2024 |title=Charting the course of pinniped evolution: insights from molecular phylogeny and fossil record integration |journal=Evolution |volume=78 |issue=7 |pages=1212–1226 |doi=10.1093/evolut/qpae061 |doi-access=free }}</ref>
}}
The German naturalist [[Johann Karl Wilhelm Illiger]] was the first to recognize the pinnipeds as a distinct [[taxonomy (biology)|taxonomic]] unit; in 1811 he gave the name Pinnipedia to both a [[Family (biology)|family]] and an [[Order (biology)|order]].<ref>{{cite book |last=Scheffer |first=Victor B. |title=Seals, Sea Lions, and Walruses: A Review of the Pinnipedia |year=1958 |publisher=Stanford University Press|page=52|isbn=978-0-8047-0544-8}}</ref> American zoologist [[Joel Asaph Allen]] reviewed the world's pinnipeds in an 1880 [[monograph]], ''History of North American pinnipeds, a monograph of the walruses, sea-lions, sea-bears and seals of North America''. In this publication, he traced the history of names, gave [[identification key|keys]] to families and genera, described North American species and provided synopses of species in other parts of the world.<ref>{{Cite book |author=Allen, J. A. |title=History of North American pinnipeds, a monograph of the walruses, sea-lions, sea-bears and seals of North America |year=1880 |series=Miscellaneous publications (Geological and Geographical Survey of the Territories (U.S.)) |location=Washington |publisher=Government Printing Office |url=https://www.biodiversitylibrary.org/item/17432#page/7/mode/1up}}</ref> In 1989, Annalisa Berta and colleagues proposed the unranked [[clade]] [[Pinnipedimorpha]] to contain the fossil genus ''[[Enaliarctos]]'' and modern seals as a [[sister group]].<ref name="Berta 1989">{{cite journal |author1=Berta, A. |author2=Ray, C. E. |author3=Wyss, A. R. |title=Skeleton of the oldest known pinniped, ''Enaliarctos mealsi'' |journal=Science |year=1989 |volume=244 |issue=4900 |pages=60–62 |jstor=1703439 |pmid=17818847 |doi=10.1126/science.244.4900.60 |bibcode=1989Sci...244...60B |s2cid=29596040 }}</ref> Pinnipeds belong to the order [[Carnivora]] and the suborder [[Caniformia]] (known as dog-like carnivorans).<ref>{{Cite journal 
|author1=Arnason, U. |author2=Gullberg, A. |author3=Janke, A. |author4=Kullberg, M. |title=Mitogenomic analyses of caniform relationships |doi=10.1016/j.ympev.2007.06.019 |journal=Molecular Phylogenetics and Evolution |volume=45 |issue=3 |pages=863–74 |year=2007 |pmid=17919938}}</ref> Of the three extant families, the [[Otariidae]] and [[Odobenidae]] are grouped in the superfamily Otarioidea,<ref>{{cite web |title=Superfamily Otarioidea Lucas 1899 |publisher=Paleobiology Database |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=41332 |access-date=1 July 2013 }}</ref> while the [[Phocidae]] belong to the superfamily Phocoidea.<ref>{{cite web|title=Superfamily Phocoidea Smirnov 1908|publisher=Paleobiology Database|url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=53273|access-date=1 July 2013|archive-date=9 March 2016|archive-url=https://web.archive.org/web/20160309215114/http://paleodb.org/?a=basictaxoninfo&taxon_no=53273|url-status=live}}</ref> There are 34 [[extant taxon|extant]] species of pinnipeds,<ref name="Berta Churchill Boessenecker 2018">{{cite journal | last1=Berta | first1=Annalisa | last2=Churchill | first2=Morgan | last3=Boessenecker | first3=Robert W. | title=The Origin and Evolutionary Biology of Pinnipeds: Seals, Sea Lions, and Walruses | journal=Annual Review of Earth and Planetary Sciences | publisher=Annual Reviews | volume=46 | issue=1 | date=2018-05-30 | issn=0084-6597 | doi=10.1146/annurev-earth-082517-010009 | pages=203–228| bibcode=2018AREPS..46..203B | s2cid=135439365 | doi-access=free }}</ref> and more than 50 fossil species of pinnipedimorphs.<ref>{{cite journal |author1=Deméré, T. A. |author2=Berta, A. |author3=Adam, P. J. |title=Pinnipedimorph evolutionary biogeography |journal=Bulletin of the American Museum of Natural History |year=2003 |volume=279 |pages=32–76 |url=http://www.sdnhm.org/archive/research/paleontology/Demere_et_al_2003.pdf |doi=10.1206/0003-0090(2003)279<0032:C>2.0.CO;2|s2cid=87939134 }}</ref>

Otariids are also known as eared seals due to their [[Pinna (anatomy)|pinnae]]. These animals swim mainly using their well-developed fore-flippers. They can also "walk" on land by shifting their hind-flippers forward under the body.{{sfn|Riedman|1990|p=64}} The front end of an otariid's [[frontal bone]] protrudes between the [[nasal bone]]s, with a large and flattened [[supraorbital foramen]]. An extra spine splits the [[supraspinatous fossa]] and [[bronchi]] that are divided in the front.<ref name="Berta"/> Otariids consist of two types: [[sea lion]]s and [[fur seal]]s; the latter typically being smaller, with pointier snouts, longer fore-flippers and heavier [[animal coat|fur coats]].{{sfn|Riedman|1990|pp=68–70}} Five [[genera]] and seven species (one now extinct) of sea lion are known to exist, while two genera and nine species of fur seal exist. While sea lions and fur seals have historically been considered separate subfamilies (Otariinae and Arctocephalinae respectively), genetic and [[molecular phylogenetics|molecular]] evidence has refuted this, indicating that the [[northern fur seal]] is [[Basal (phylogenetics)|basal]] to other otariids and the [[Australian sea lion]] and [[New Zealand sea lion]] are more closely related to ''[[Arctocephalus]]'' than to other sea lions.<ref name="Berta Churchill Boessenecker 2018"/>

Odobenidae has only one living member: the [[walrus]]. This animal is noticeable from its larger size (exceeded only by the [[elephant seals]]), nearly hairless skin, flattened snout and long upper [[Canine tooth|canines]], known as [[tusk]]s. Like otariids, walruses can walk on land with their hind limbs. When moving in water, the walrus relies on its hind limbs for locomotion, while its forelimbs are used for steering. Also, it has no outer ears.{{sfn|Riedman|1990|pp=3, 82–83}}<ref name=Kastelein/> The [[epipterygoid]] of the jaw is well developed and the back of the nasal bones are horizontal. In the feet, the [[calcaneus]]es protrude in the middle.<ref name="Berta"/>

Phocids are known as true or "earless" seals. These animals lack outer ears and cannot position their hind-flippers to move on land, making them more cumbersome. This is because of their massive [[ankle bone]]s and flatter heels. In water, true seals rely on the side-to-side motion of their hind-flippers and lower body to move forward.{{sfn|Riedman|1990|p=64}} The phocid's skull has [[Pachyostosis|thickened]] [[Mastoid process|mastoid]]s, puffed up [[Temporal bone#In other animals|entotympanic bone]]s, nasal bones with a pointed tip in the back and a non-existent supraorbital foramen. The hip has a more converse [[Ilium (bone)|ilium]].<ref name="Berta"/> A 2006 molecular study supports the division of phocids into two monophyletic subfamilies: Monachinae, which consists of elephant seals, [[monk seals]] and [[Lobodontini|Antarctic seals]]; and Phocinae, which consists of all the rest.<ref name="Berta Churchill Boessenecker 2018"/><ref name="Berta"/>

===Evolution===
{{Further|List of fossil pinnipedimorphs}}
[[File:Puijila BW.jpg|thumb|right|Restoration of ''Puijila'']]
One popular hypothesis suggested that pinnipeds are [[polyphyletic|diphyletic]] (descended from two ancestral lines), with walruses and otariids sharing a [[Most recent common ancestor|recent common ancestor]] with [[bear]]s; and phocids sharing one with [[Musteloidea]]. However, morphological and molecular evidence support a [[monophyletic]] origin.<ref name="Berta">Berta, A. "Pinniped evolution" in {{harvnb|Perrin|Würsig|Thewissen|2009|pp=861–866}}</ref> A 2021 genetic study found that pinnipeds are more closely related to musteloids.<ref>{{cite journal|author1=Hassanin, A.|author2=Veron, G.|author3=Ropiquet, A.|author4=van Vuuren, B. J.|author5=Lécu, A.|author6=Goodman, S. M.|author7=Haider, J.|author8=Nguyen, T. T.|year=2021|title=Evolutionary history of Carnivora (Mammalia, Laurasiatheria) inferred from mitochondrial genomes|journal=PLOS ONE|volume=16|issue=2|page=e0240770|doi=10.1371/journal.pone.0240770|pmid=33591975 |pmc=7886153 |bibcode=2021PLoSO..1640770H |doi-access=free }}</ref> Pinnipeds [[Cladogenesis|split]] from other caniforms 50&nbsp;million years ago ([[Mya (unit)|mya]]) during the [[Eocene]].<ref name=leptin>{{cite journal |vauthors=Hammond JA, Hauton C, Bennett KA, Hall AJ |year=2012 |title=Phocid seal leptin: Tertiary structure and hydrophobic receptor binding site preservation during distinct leptin gene evolution |journal=PLOS ONE |volume=7 |issue=4 |page=e35395 |doi=10.1371/journal.pone.0035395 |editor1-last=Nikolaidis |editor1-first=Nikolas |bibcode=2012PLoSO...735395H |pmid=22536379 |pmc=3334926|doi-access=free }}</ref> The earliest fossils of pinnipeds date back to the [[Chattian|Late Oligocene]].<ref>{{Cite journal |last=Valenzuela-Toro |first=Ana |last2=Pyenson |first2=Nicholas D. |date=27 November 2019 |title=What do we know about the fossil record of pinnipeds? A historiographical investigation |url=https://royalsocietypublishing.org/doi/10.1098/rsos.191394 |journal=[[Royal Society Open Science]] |language=en |volume=6 |issue=11 |pages=191394 |doi=10.1098/rsos.191394 |issn=2054-5703 |pmc=6894555 |pmid=31827869 |access-date=13 November 2024}}</ref> Fossil animals representing basal lineages include ''[[Puijila]]'', of the [[Early Miocene]] in Arctic Canada. It resembled a modern otter, but shows evidence of quadrupedal swimming—retaining a form of aquatic locomotion that led to those employed by modern pinnipeds. ''[[Potamotherium]]'', which lived in the same period in Europe, was similar to ''Puijila'' but more aquatic.<ref name="Dawson2009">{{Cite journal |author1=Rybczynski, N. |author2=Dawson, M. R. |author3=Tedford, R. H. |doi=10.1038/nature07985 |title=A semi-aquatic Arctic mammalian carnivore from the Miocene epoch and origin of Pinnipedia |journal=Nature |volume=458 |issue=7241 |pages=1021–24 |year=2009 |pmid=19396145|bibcode=2009Natur.458.1021R |s2cid=4371413 }}</ref> The braincase of ''Potamotherium'' shows evidence that it used its [[whiskers]] to hunt, like modern seals.<ref>{{Cite journal |last1=Lyras |first1=G. A. |last2=Werdelin |first2=L |last3=van der Geer |first3=B. G. M. |last4=van der Geer |first4=A. A. E. |year=2023 |title=Fossil brains provide evidence of underwater feeding in early seals |journal=Communications Biology |language=en |volume=6 |issue=1 |page=747 |doi=10.1038/s42003-023-05135-z |pmid=37591929 |issn=2399-3642|pmc=10435510 }}</ref> Both ''Puijila'' and ''Potamotherium'' fossils have been found in lake deposits, suggesting that seal ancestors were originally adapted for fresh water.<ref name="Dawson2009"/>

[[File:Enaliarctos mealsi.JPG|left|thumb|Fossil of ''Enaliarctos'']]
''Enaliarctos'', a fossil species of late [[Oligocene]]/early Miocene (24–22&nbsp;mya) [[California]], closely resembled modern pinnipeds; it was adapted to an aquatic life with flippers and a flexible spine. Its teeth were more like land predators in that they were more adapted for [[Carnassial|shearing]]. Its hind-flippers may have allowed it to walk on land, and it probably did not leave coastal areas as much as its modern relatives. ''Enaliarctos'' was likely more of a fore-flipper swimmer, but could probably swim with either pair.<ref name="Berta"/> One species, ''Enaliarctos emlongi'', exhibited notable [[sexual dimorphism]], suggesting that this physical characteristic may have been an important driver of pinniped evolution.<ref name=Cullenetal2014>{{cite journal|last1=Cullen|first1=T. M.|last2=Fraser|first2=D.|last3=Rybczynski|first3=N.|last4=Shroder-Adams|first4=C.|title=Early evolution of sexual dimorphism and polygyny in Pinnipeda|journal=Evolution|date=2014|volume=68|issue=5|pages=1469–1484|doi=10.1111/evo.12360|pmid=24548136|s2cid=10389875|doi-access=free}}</ref> A closer relative of extant pinnipeds was ''[[Pteronarctos]]'', which lived in [[Oregon]] 19–15 mya. As in modern seals, the [[maxilla]] or upper jaw bone of ''Pteroarctos'' intersects with the [[Orbit (anatomy)|orbital wall]]. The extinct family [[Desmatophocidae]] lived 23–10&nbsp;mya in the North Pacific. They had long skulls that with large orbits, interlocked [[zygomatic bone]]s and rounded [[molar (tooth)|molar]]s and [[premolars]]. They also were sexually dimorphic and may have been capable of swimming with both or either pair of flippers.<ref name="Berta"/> They are grouped with modern pinnipeds, but there is debate as to whether they are more closely related to phocids or to otariids and walruses.<ref>{{cite journal|last1=Boessenecker|first1=R. W.|last2=Churchill|first2=M.|year=2018|title=The last of the desmatophocid seals: a new species of ''Allodesmus'' from the upper Miocene of Washington, USA, and a revision of the taxonomy of Desmatophocidae|journal=Zoological Journal of the Linnean Society|volume=184|issue=1|pages=211–235|doi=10.1093/zoolinnean/zlx098}}</ref><ref name="Berta Churchill Boessenecker 2018"/> A 2024 study places them within Phocidae, specifically Phocinae.<ref name=Park2024/>

[[Image:Archaeodobenus restoration.PNG|thumb|Reconstruction of ''[[Archaeodobenus]] akamatsui'' family Odobenidae]]
The ancestors of the Otarioidea and Phocoidea diverged around 25&nbsp;mya.<ref name=Nyakatura>{{cite journal|last1=Nyakatura|first1=K|last2=Bininda-Emonds|first2=O. R. P.|year=2012|title=Updating the evolutionary history of Carnivora (Mammalia): a new species-level supertree complete with divergence time estimates|journal=BMC Biology|volume=10|page=12|doi=10.1186/1741-7007-10-12|doi-access=free|pmid=22369503|pmc=3307490}}</ref> Phocids are known to have existed for at least 15&nbsp;million years,<ref name="Berta"/> and molecular evidence supports a divergence of the Monachinae and Phocinae lineages around this time.<ref name="Berta Churchill Boessenecker 2018"/> The fossil genera ''[[Monotherium]]'' and ''[[Leptophoca]]'' of southeastern North America represent the earliest members of Monachinae and Phocinae respectively.<ref name="Berta"/> Both lineages may have originated in the North Atlantic, and likely reached the Pacific via the [[Central American Seaway]]. Phocines mainly stayed in the Northern Hemisphere, while the monachines diversified southward.<ref name="Berta Churchill Boessenecker 2018"/> The [[Lineage (evolution)|lineages]] of Otariidae and Odobenidae split around 20&nbsp;mya.<ref name=Nyakatura/> The earliest fossil records of otariids are in North Pacific and dated to around 11&nbsp;mya. Early fossil genera include ''[[Pithanotaria]]'' and ''[[Thalassoleon]]''.<ref name="Berta"/> The ''Callorhinus'' lineage split the earliest, followed by the ''[[Eumetopias]]''/''[[Zalophus]]'' lineage and then the rest, which colonized the Southern Hemisphere.<ref name="Berta"/><ref name="Berta Churchill Boessenecker 2018"/> The earliest fossils of Odobenidae—''[[Prototaria]]'' of Japan and ''[[Proneotherium]]'' of Oregon—date to 18–16&nbsp;mya. These primitive walruses had normal sized canines and fed on fish instead of mollusks. Later taxa like ''[[Gomphotaria]]'', ''[[Pontolis]]'' and ''[[Dusignathus]]'' had longer canines on both the upper and lower jaw. The familiar long upper tusks developed in the genera ''[[Valenictus]]'' and ''Odobenus''. The lineage of the modern walrus may have spread from the North Pacific to the North Atlantic through the Caribbean and Central American Seaway 8–5&nbsp;mya, and then back to the North Pacific via the Arctic 1&nbsp;mya, or to the Arctic and subsequently the North Atlantic during the [[Pleistocene]].<ref name="Berta"/>