Editing Hippopotamidae

{{Short description|Family of mammals}}
{{Hatnote|For the common hippopotamid species, see [[Hippopotamus]]}}
{{Use dmy dates|date=August 2020}}
{{Automatic taxobox
| fossil_range = {{fossilrange|7.4|0}} Late [[Miocene]]-Recent
| image = Hippo pod edit.jpg
| image_caption = [[Common hippopotamus]]
| image2 = Choeropsis.jpg
| image2_caption = [[Pygmy hippopotamus]]
| taxon = Hippopotamidae
| authority = [[John Edward Gray|Gray]], 1821
| display_parents = 2
| subdivision_ranks = Subtaxa
| subdivision = †''[[Trilobophorus]]'' <small>Geze, 1985</small>

*Hippopotaminae <small>Gray, 1821</small>
** †''[[Archaeopotamus]]''
** ''[[Choeropsis]]''
** †''[[Hexaprotodon]]''
** ''[[Hippopotamus (genus)|Hippopotamus]]''
** †''[[Saotherium]]''
*†Kenyapotaminae <small>Pickford, 1983</small>
** ''[[Kenyapotamus]]''
** ''[[Palaeopotamus]]''
}}

'''Hippopotamidae''' is a [[family (biology)|family]] of stout, [[Pachydermata|naked-skinned]], and [[semiaquatic]] [[artiodactyl]] mammals, possessing three-chambered stomachs and walking on four toes on each foot. While they resemble [[suinae|pigs]] physiologically, their closest living relatives are the [[cetacean]]s. They are formally referred to as '''hippopotamids'''.

There are two living species of hippopotamid in two genera; the pygmy hippo, ''[[Choeropsis liberiensis]]'' of the forests of west Africa, and the common hippo, ''[[Hippopotamus amphibius]]''. The term ''hippopotamus'' can also be applied to hippopotamids in general, although it is most frequently used for the common hippo and its respective [[genus]].

== Characteristics ==
Hippopotamids are large mammals, with short, stumpy legs, and barrel-shaped bodies. They have large heads, with broad mouths, and nostrils placed at the top of their snouts. Like pigs, they have four toes, but unlike pigs, all of the toes are used in walking. Hippopotamids are [[unguligrade]], although, unlike most other such animals, they have no hooves, instead using a pad of tough connective tissue on each foot. Their stomachs have three chambers, but they are not true [[ruminant]]s.

The living species are smooth-skinned and lack both [[sebaceous gland]]s and [[sweat gland]]s. The outer [[Epidermis (skin)|epidermis]] is relatively thin, so hippos dehydrate rapidly in dry environments.<ref name=EoM>{{cite book|editor= Macdonald, D.|author= Laws, Richard|year= 1984|title= The Encyclopedia of Mammals|publisher= Facts on File|location= New York|pages= [https://archive.org/details/encyclopediaofma00mals_0/page/506 506–511]|isbn= 0-87196-871-1|url-access= registration|url= https://archive.org/details/encyclopediaofma00mals_0/page/506}}</ref>

Both the [[incisor]]s and [[canine (tooth)|canine]]s are large and tusk-like, although the canine tusks are by far the larger. The tusks grow throughout life. The postcanine teeth are large and complex, suited for chewing the plant matter that comprises their diets. The number of incisors varies even within the same species, but the general [[dentition|dental formula]] is given in the table below: {{dentition2|2–3.1.4.3|1–3.1.4.3}}

== Evolution ==
{{Main|Hippopotamus#Evolution|l1=Evolution of hippopotamids}}
[[File:Hippopotamus_amphibius_Linn_at_Ghar_Dalam,_Malta.png|thumb|right|Hippopotamus skeleton at [[Għar Dalam]]]]
The hippopotamids are descended from the [[anthracothere]]s, a family of semiaquatic and terrestrial artiodactyls that appeared in the late [[Eocene]], and are thought to have resembled small- or narrow-headed hippos.  The hippos split off from the anthracotheres some time during the [[Miocene]]. The oldest records of Hippopotamidae are from Afro-Arabia and date to the late Miocene, approximately 7.4 million years ago, expanding into Eurasia around 6 million years ago.<ref>{{Cite journal |last1=Martino |first1=R. |last2=Pandolfi |first2=L. |date=2022-07-03 |title=The Quaternary Hippopotamus records from Italy |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2021.1965138 |journal=Historical Biology |language=en |volume=34 |issue=7 |pages=1146–1156 |doi=10.1080/08912963.2021.1965138 |bibcode=2022HBio...34.1146M |s2cid=239713930 |issn=0891-2963}}</ref> After the appearance of the hippopotamids, the remaining anthracotheres went into a decline brought about by a combination of climatic change and competition with their descendants, until the last genus, ''[[Merycopotamus]]'', died out in the early [[Pliocene]] of India.

There were once many species of hippopotamid, but only two survive today: ''Hippopotamus amphibius'', and ''Choeropsis liberiensis''. They are the last survivors of two major [[evolution]]ary lineages, the hippos proper and the pygmy hippos, respectively; these lineages could arguably be considered [[subfamilies]], but their relationship to each other – apart from being fairly distant relatives – is not well resolved.

The enigmatic [[Miocene]] ''[[Kenyapotamus]]'' is insufficiently known to be assigned a place in the hippo [[phylogeny]] with any degree of certainty. In addition, the genus ''[[Hexaprotodon]]'', which is now largely restricted to South Asia and Southeast Asia, formerly included many fossil hippopotamuses that are now thought to be unrelated.<ref name="Linnean">{{cite journal |last=Boisserie |first=Jean-Renaud |year=2005 |title=The phylogeny and taxonomy of Hippopotamidae (Mammalia: Artiodactyla): a review based on morphology and cladistic analysis |journal=[[Zoological Journal of the Linnean Society]] |volume=143 |pages=1–26 |doi=10.1111/j.1096-3642.2004.00138.x |doi-access=free}}</ref>

=== Taxonomy ===
Hippopotamidae's placement within [[Artiodactyla]] can be represented in the following [[cladogram]]:<ref>
{{cite journal
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 |last5=  Giallombardo |first5= A.     |last6= Giannini |first6= N.P.
 |last7=  Goldberg   |first7= S.L.     |last8= Kraatz   |first8= B.P.
 |last9=  Luo        |first9= Z.-X.    |last10= Meng    |first10= J.
 |last11= Ni         |first11= X.      |last12= Novacek |first12= M.J.
 |last13= Perini     |first13= F.A.    |last14= Randall |first14= Z.S.
 |last15= Rougier    |first15= G.W.    |last16= Sargis  |first16= E.J.
 |last17= Silcox     |first17= M.T.    |last18= Simmons |first18= N.B.
 |last19= Spaulding  |first19= M.      |last20= Velazco |first20= P.M.
 |last21= Weksler    |first21= M.      |last22= Wible   |first22= J.R.
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</ref><ref name="Song2012">
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</ref><ref name="dos Reis2012">
{{cite journal
 |last1= dos Reis |first1= M.        |last2= Inoue |first2= J.
 |last3= Hasegawa |first3= M.        |last4= Asher |first4= R.J.
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</ref><ref name=Upham2019>
{{cite journal
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 |last3= Jetz |first3= W.
 |year= 2019
 |title= Inferring the mammal tree: Species-level sets of phylogenies for questions in ecology, evolution, and conservation
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 |pmid= 31800571 |pmc= 6892540 |postscript=;
}} (see fig&nbsp;S10).
</ref>

{{Clade
     |style=font-size:100%;line-height:100%
     |label1=[[Artiodactyla]]
     |1={{Clade
         |1=[[Tylopoda]] (camels and kin) [[File:Cladogram of Cetacea within Artiodactyla (Camelus bactrianus).png|50 px]]
         |label2=[[Artiofabula]]
         |2={{Clade
               |1=[[Suina]] (pigs and kin) [[File:Recherches pour servir à l'histoire naturelle des mammifères (Pl. 80) (white background).jpg|50 px]]
               |label2=[[Cetruminantia]]
               |2={{Clade
                   |1=[[Ruminantia]] (ruminants) [[File:Walia ibex illustration white background.png|50 px]]
                   |label2=[[Whippomorpha]]
                   |sublabel2=(or Cetancodonta)
                   |2={{Clade
                      |1='''Hippopotamidae''' (hippopotamids) [[File:Voyage en Abyssinie Plate 2 (white background).jpg|50 px]]
                      |2=[[Cetacea]] (whales) [[File:Bowhead-Whale1 (16273933365).jpg|50 px]]
                      }}
                  }}
               }}
            }}
         }}

=== Analogous structures ===
The lower canine teeth of hippopotamids are similar in function and structure to the tusks of [[elephant]]s. While hippopotamids and elephants are only very distantly related within the Mammalia, the lower canine teeth of both groups are long and have a slight curve, and species of both families use this structure when fighting.

== Species ==
The systematics and [[Taxonomy (biology)|taxonomy]] used here mostly follows a review by J.-R. Boisserie<ref name=Boisserie-2005>
{{cite journal
 |author=Boisserie, Jean-Renaud
 |year=2005
 |title=The phylogeny and taxonomy of Hippopotamidae (Mammalia: Artiodactyla): A review based on morphology and cladistic analysis
 |journal=[[Zoological Journal of the Linnean Society]]
 |volume=143 |issue=1 |pages=1–26
 |doi=10.1111/j.1096-3642.2004.00138.x
 |type=HTML abstract
|doi-access=free
 }}
</ref>{{efn|name=hippo-minor|
Boisserie (2005)<ref name=Boisserie-2005/> identified the species ''Hippopotamus minor'' as ''Phanourios minutus'', but this genus is not widely recognized.
}}
and the [[American Society of Mammalogists]].<ref>
{{cite web
 |author1=Upham, Nathan      |author2=Burgin, Connor   |author3=Widness, Jane
 |author4=Liphardt, Schuyler |author5=Parker, Camila   |author6=Becker, Madeleine
 |author7=Rochon, Ingrid     |author8=Huckaby, David   |display-authors=6
 |date=10 August 2021
 |orig-year=2004
 |title=Mammal Diversity Database
 |type=vers.&nbsp;1.6
 |publisher=[[American Society of Mammalogists]]
 |doi=10.5281/zenodo.5175993
 |url=https://zenodo.org/record/5175993
 |access-date=2021-08-28
}}
</ref>

=== Recent species ===

* Genus ''[[Hippopotamus (genus)|Hippopotamus]]'' – true hippopotamuses
** ''[[Hippopotamus amphibius]]'' – hippopotamus ([[Africa]])
**†''[[Hippopotamus lemerlei]]'' – Lemerle's dwarf hippopotamus ([[Madagascar]]; [[Holocene]])
**†''[[Hippopotamus madagascariensis]]'' – Madagascan dwarf hippopotamus ([[Madagascar]]; [[Holocene]])
* Genus ''[[Choeropsis]]'' – pygmy hippopotamuses
** ''[[Pygmy hippopotamus|Choeropsis liberiensis]]'' – pygmy hippopotamus (west Africa)

=== Fossil species ===
* Genus ''[[Hippopotamus (genus)|Hippopotamus]]'' – true hippopotamuses
** †''[[Hippopotamus antiquus]]'' – mainland [[Europe]] & [[British Isles]]; [[Pleistocene]]
** †''[[Hippopotamus creutzburgi]]'' – [[Crete]]; Pleistocene
** †''[[Hippopotamus minor]]''{{efn|name=hippo-minor}} – [[Cyprus]]; Pleistocene to [[Holocene]]
** †''[[Hippopotamus melitensis]]'' – [[Malta]]; Pleistocene
** †''[[Hippopotamus pentlandi]]'' – Sicily; Pleistocene
** †''[[Hippopotamus laloumena]]'' – Madagascar; Holocene
** †''[[Hippopotamus gorgops]]'' – Africa [[Late Miocene]]–[[Middle Pleistocene]]
* Tentatively placed into ''Hippopotamus'':
** †''[[Hippopotamus aethiopicus]]'' – Kenya & Ethiopia; Pliocene -Pleistocene
** †''[[Hippopotamus afarensis]]'' – Ethiopia, formerly genus ''Trilobophorus''; Pliocene
** †''[[Hippopotamus behemoth]]'' – [[Israel]], Early Pleistocene
** †''[[Hippopotamus kaisensis]]'' – Central Africa; Pliocene
** †''[[Hippopotamus sirensis]]'' – [[Morocco]] & [[Algeria]]; Pleistocene
* Genus ''[[Hexaprotodon]]'' – hexaprotodons or Asian hippopotamuses
** †''[[Hexaprotodon bruneti]]'' – [[Ethiopia]]; Pliocene
** †''[[Hexaprotodon coryndoni]]'' – Ethiopia; Pliocene
** †''[[Hexaprotodon crusafonti]]'' – [[Spain]]; Late Miocene (syn. ''Hexaprotodon primaevus'')
** †''[[Hexaprotodon hipponensis]]'' – [[Algeria]]
** †''[[Hexaprotodon imagunculus]]'' – [[Uganda]] and [[Congo Basin|Congo]]; Pliocene
** †''[[Hexaprotodon iravaticus]]'' – [[Myanmar]]; Pliocene – Pleistocene
** †''[[Hexaprotodon karumensis]]'' – Kenya and [[Eritrea]]; Pleistocene
** †''[[Hexaprotodon namadicus]]'' – [[India]]; (possibly same as ''Hex. palaeindicus'')
** †''[[Hexaprotodon palaeindicus]]'' – India;
** †''[[Hexaprotodon pantanellii]]'' – [[Italy]]; Pliocene
** †''[[Hexaprotodon protamphibius]]'' – Kenya and Chad; Pliocene
** †''[[Hexaprotodon siculus]]'' –
** †''[[Hexaprotodon sivajavanicus]]'' – Indonesia
** †''[[Hexaprotodon sivalensis]]'' – India
** †''Hexaprotodon'' sp. (undescribed) – Myanmar
* Genus ''[[Archaeopotamus]]'' – formerly included in ''Hexaprotodon''
** †''Archaeopotamus harvardi'' –  [[Arabian Peninsula]] and Central Africa; [[Miocene]] – [[Pliocene]]
** †''Archaeopotamus lothagamensis'' – [[Kenya]]; Miocene
* One or two undescribed species
* Genus ''[[Saotherium]]'' – formerly included in ''Hexaprotodon''
** †''{{ill|Saotherium mingoz|it}}'' [[Chad]]; Pliocene

== See also ==
* [[List of individual hippopotamids]]

== Footnotes ==
{{Notelist}}

== References ==
{{Reflist|25em}}

==Further reading==
* {{ITIS |id=624917 |taxon=Hippopotamidae |access-date=11 August 2004}}
* {{cite journal
 |author=Petronio, C.
 |year=1995
 |title=Note on the taxonomy of Pleistocene hippopotamuses
 |journal=[[Ibex (journal)|Ibex]]
 |volume=3 |pages=53–55
 |url=http://www.mountainecology.org/IBEX3/pdf/Art_Capitolo1/note_taxonomy_pleistocene.pdf
 |url-status=dead <!-- presumed -->
 |archive-url=https://web.archive.org/web/20080912012236/http://www.mountainecology.org/IBEX3/pdf/Art_Capitolo1/note_taxonomy_pleistocene.pdf
 |archive-date=2008-09-12
}}

{{Artiodactyla|C.}}
{{Taxonbar|from=Q213336}}
{{Authority control}}

[[Category:Hippopotamuses| ]]
[[Category:Ancodonta]]
[[Category:Mammal families]]
[[Category:Langhian first appearances]]
[[Category:Extant Miocene first appearances]]
[[Category:Taxa named by John Edward Gray]]