Hippopotamidae
| Hippopotamidae Temporal range: Late Miocene-Recent
| |
|---|---|
| |
Common hippopotamus
| |
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| Pygmy hippopotamus | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Suborder: | Whippomorpha |
| Superfamily: | Hippopotamoidea
|
| Family: | Hippopotamidae Gray, 1821 |
| Subtaxa | |
|
†Trilobophorus Geze, 1985
| |
Hippopotamidae is a
cetaceans
. They are sometimes referred to as hippopotamids.
There are two living species of hippopotamid in two genera; the pygmy 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 ruminants
.
The living species are smooth-skinned and lack both
epidermis is relatively thin, so hippos dehydrate rapidly in dry environments.[1]
Both the
canines 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 dental formula
is given in the table below:
| Dentition |
|---|
| 2–3.1.4.3 |
| 1–3.1.4.3 |
Evolution
The hippopotamids are descended from the
anthracotheres, 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.[2] 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
subfamilies
, but their relationship to each other – apart from being fairly distant relatives – is not well resolved.
The enigmatic
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.[3]
Taxonomy
Hippopotamidae's placement within
| Artiodactyla
|
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Analogous structures
The lower canine teeth of hippopotamids are similar in function and structure to the tusks of elephants. 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 used here mostly follows a review by J.-R. Boisserie[9][a] and the American Society of Mammalogists.[10]
Recent species
- 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
- Choeropsis liberiensis – pygmy hippopotamus (west Africa)
Fossil species
- Genus Hippopotamus – true hippopotamuses
- †Hippopotamus antiquus – mainland Europe & British Isles; Pleistocene
- †Hippopotamus creutzburgi – Crete; Pleistocene
- †
- †Hippopotamus melitensis – Malta; Pleistocene
- †Hippopotamus pentlandi – Sicily; Pleistocene
- †Hippopotamus laloumena – Madagascar; Holocene
- †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
- †; 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; 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
- †Saotherium mingoz Chad; Pliocene
Footnotes
References
- ISBN 0-87196-871-1.
- S2CID 239713930.
- .
- ^
Beck, N.R. (2006). "A higher-level MRP supertree of placental mammals". BMC Evol Biol. 6: 93. PMID 17101039.
- ^
O'Leary, M.A.; Bloch, J.I.; Flynn, J.J.; Gaudin, T.J.; Giallombardo, A.; Giannini, N.P.; et al. (2013). "The placental mammal ancestor and the post-K-Pg radiation of placentals". Science. 339 (6120): 662–667. S2CID 206544776.
- ^
Song, S.; Liu, L.; Edwards, S.V.; Wu, S. (2012). "Resolving conflict in eutherian mammal phylogeny using phylogenomics and the multispecies coalescent model". Proceedings of the National Academy of Sciences. 109 (37): 14942–14947. PMID 22930817.
- ^
dos Reis, M.; Inoue, J.; Hasegawa, M.; Asher, R.J.; Donoghue, P.C.J.; Yang, Z. (2012). "Phylogenomic datasets provide both precision and accuracy in estimating the timescale of placental mammal phylogeny". Proceedings of the Royal Society B: Biological Sciences. 279 (1742): 3491–3500. PMID 22628470.
- ^
Upham, N.S.; Esselstyn, J.A.; Jetz, W. (2019). "Inferring the mammal tree: Species-level sets of phylogenies for questions in ecology, evolution, and conservation". PLOS Biology. 17 (12): e3000494. PMID 31800571; (see fig S10).
- ^ a b Boisserie, Jean-Renaud (2005). "The phylogeny and taxonomy of Hippopotamidae (Mammalia: Artiodactyla): A review based on morphology and cladistic analysis". .
- ^ Upham, Nathan; Burgin, Connor; Widness, Jane; Liphardt, Schuyler; Parker, Camila; Becker, Madeleine; et al. (10 August 2021) [2004]. "Mammal Diversity Database" (vers. 1.6). . Retrieved 28 August 2021.
Further reading
- "Hippopotamidae". Integrated Taxonomic Information System. Retrieved 11 August 2004.
- Petronio, C. (1995). "Note on the taxonomy of Pleistocene hippopotamuses" (PDF). Ibex. 3: 53–55. Archived from the original (PDF) on 12 September 2008.