Paenungulata

Paenungulata (from Latin paene "almost" + ungulātus "having hoofs") is a clade of "sub-ungulates", which groups three extant mammal orders: Proboscidea (including elephants), Sirenia (sea cows, including dugongs and manatees), and Hyracoidea (hyraxes). At least two more possible orders are known only as fossils, namely Embrithopoda and Desmostylia.[lower-alpha 1]

Paenungulata
Temporal range: Paleocene - Recent,
Top: Rock hyrax (Hyracoidea), Arsinoitherium zitteli (Embrithopoda); bottom: Asian elephant (Proboscidea), West Indian manatee (Sirenia).
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Superorder: Afrotheria
Clade: Paenungulata
Simpson, 1945
Subgroups

Molecular evidence indicates that Paenungulata (or at least its extant members) is part of the cohort Afrotheria, an ancient assemblage of mainly African mammals of great diversity. The other members of this cohort are the orders Afrosoricida (tenrecs and golden moles), Macroscelidea (elephant shrews) and Tubulidentata (aardvarks).[6]

Of the five orders, hyraxes are the most basal, followed by embrithopods; the remaining orders (sirenians and elephants) are more closely related. These latter three are grouped as the Tethytheria, because it is believed that their common ancestors lived on the shores of the prehistoric Tethys Sea; however, recent myoglobin studies indicate that even Hyracoidea had an aquatic ancestor.[7]

History

In 1945, George Gaylord Simpson used traditional taxonomic techniques to group these spectacularly diverse mammals in the superorder he named Paenungulata ("almost ungulates"), but there were many loose threads in unravelling their genealogy.[8] For example, hyraxes in his Paenungulata had some characteristics suggesting they might be connected to the Perissodactyla (odd-toed ungulates, such as horses and rhinos). Indeed, early taxonomists placed the Hyracoidea closest to the rhinoceroses because of their dentition.

When genetic techniques were developed for inspecting amino acid differences among haemoglobin sequences the most parsimonious cladograms depicted Simpson's Paenungulata as an authentic clade and as one of the first groups to diversify from the basal placental mammals (Eutheria). The amino acid sequences reject a connection between extant paenungulates and perissodactyls (odd-toed ungulates).[8]

However, a 2014 cladistic analysis placed anthracobunids and desmostylians, two major extinct groups that have been considered to be non-African afrotheres, close to each other within Perissodactyla.[5]

Phylogeny
Afrotheria
Afroinsectiphilia
Tubulidentata

Orycteropodidae

Afroinsectivora
Macroscelidea

Macroscelididae

Afrosoricida

Chrysochloridae

Tenrecomorpha

Potamogalidae

Tenrecidae

Paenungulata
Hyracoidea

Procaviidae

Tethytheria
Proboscidea

Elephantidae

Sirenia

Dugongidae

Trichechidae

A cladogram of Afrotheria based on molecular evidence[9]

Extinct orders

Each of the extinct orders, the Embrithopoda and Desmostylia,[lower-alpha 1] was as unique in its members' ways of making a living as the three orders that survive. Embrithopods were rhinoceros-like herbivorous mammals with plantigrade feet, and desmostylians were hippopotamus-like amphibious animals. Their walking posture and diet have been the subject of speculation, but tooth wear indicates that desmostylians browsed on terrestrial plants and had a posture similar to other large hoofed mammals.[6]

See also

Notes
  1. Desmostylians, however, have been placed in Perissodactyla by a 2014 cladistic analysis,[5] and the taxonomic placement of embrithopods has also been questioned[3] though recently supported.[4]

References
  1. Gheerbrant, Emmanuel; Filippo, Andrea; Schmitt, Arnaud (2016). "Convergence of Afrotherian and Laurasiatherian Ungulate-Like Mammals: First Morphological Evidence from the Paleocene of Morocco". PLOS ONE. 11 (7): e0157556. Bibcode:2016PLoSO..1157556G. doi:10.1371/journal.pone.0157556. PMC 4934866. PMID 27384169.
  2. Avilla, Leonardo S.; Mothé, Dimila (2021). "Out of Africa: A New Afrotheria Lineage Rises From Extinct South American Mammals". Frontiers in Ecology and Evolution. 9. doi:10.3389/fevo.2021.654302. ISSN 2296-701X.
  3. Erdal, O.; Antoine, P.-O.; Sen, S.; Smith, A. (2016). "New material of Palaeoamasia kansui (Embrithopoda, Mammalia) from the Eocene of Turkey and a phylogenetic analysis of Embrithopoda at the species level" (PDF). Palaeontology. 59 (5): 631–655. doi:10.1111/pala.12247. S2CID 89418652.
  4. E. Gheerbrant; A. Schmitt; L. Kocsis (2018). "Early African fossils elucidate the origin of embrithopod mammals". Current Biology. 28 (13): 2167–2173.e2. doi:10.1016/j.cub.2018.05.032. PMID 30008332.
  5. Cooper, L. N.; Seiffert, E.R.; Clementz, M.; Madar, S.I.; Bajpai, S.; Hussain, S.T.; Thewissen, J.G.M. (2014). "Anthracobunids from the Middle Eocene of India and Pakistan Are Stem Perissodactyls". PLOS ONE. 9 (10): e109232. Bibcode:2014PLoSO...9j9232C. doi:10.1371/journal.pone.0109232. PMC 4189980. PMID 25295875.
  6. Kleinschmidt, Traute; Czelusniak, John; Goodman, Morris; Braunitzer, Gerhard (1986). "Paenungulata: A comparison of the hemoglobin sequences from Elephant, Hyrax, and Manatee" (PDF). Mol. Biol. Evol. 3 (5): 427–435. doi:10.1093/oxfordjournals.molbev.a040411. PMID 3444412. Archived from the original (PDF) on 30 June 2010. Retrieved 24 July 2010.
  7. "One Protein Shows Elephants and Moles Had Aquatic Ancestors". National Geographic Society. 13 June 2013.
  8. Seiffert, Erik; Guillon, J.M. (2007). "A new estimate of Afrotherian phylogeny based on simultaneous analysis of genomic, morphological, and fossil evidence". BMC Evolutionary Biology. 7: 13. doi:10.1186/1471-2148-7-224. PMC 2248600. PMID 17999766.
  9. Tabuce, R.; Asher, R. J.; Lehmann, T. (2008). "Afrotherian mammals: a review of current data" (PDF). Mammalia. 72: 2–14. doi:10.1515/MAMM.2008.004. S2CID 46133294.

Sources
  • McKenna, M.C.; Bell, S.K., eds. (1997). Classification of Mammals above the Species Level. New York, NY: Columbia University Press. ISBN 0-231-11013-8.

Further reading
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