Wikipedia

Afrotheria

Afrotheria(/æfroʊˈθɪəriə/fromLatinAfro-"of Africa" +theria"wild beast" ) is asuperorderofplacental mammals,the living members of which belong to groups that are either currently living inAfricaor of African origin:golden moles,elephant shrews(also known as sengis),otter shrews,tenrecs,aardvarks,hyraxes,elephants,sea cows,and several extinct clades. Most groups of afrotheres share little or no superficial resemblance, and their similarities have only become known in recent times because of genetics and molecular studies. Many afrothere groups are found mostly or exclusively in Africa, reflecting the fact that Africa was an island continent from theCretaceousuntil the earlyMiocenearound 20 million years ago, when Afro-Arabia collided with Eurasia.

Afrotheria
Temporal range:Paleocene–Holocene,65–0Ma
1.Aardvark2.Dugong3.Black and rufous elephant shrew4.West Indian manatee5.Cape golden mole6.Rock hyrax7.African bush elephant8.Tailless tenrec
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Infraclass: Placentalia
Superorder: Afrotheria
Stanhope MJ, Waddell VG, Madsen O, de Jong W, Hedges SB, Cleven G, Kao D, Springer MS, 1998
Orders

Seebelow

Because Africa was isolated by water,Laurasiangroups of mammals such asinsectivores,rodents,lagomorphs,carnivoransandungulatescould not reach Africa for much of the early to mid-Cenozoic.Instead, the niches occupied by those groups on the northern continents were filled by various groups of afrotheres via the process ofconvergent evolution.The small insectivorous afrotheres such as elephant shrews, golden moles, and tenrecs filled the niches ofinsectivores,the hyraxes filled the roles of rodents and lagomorphs, the aardvarks filled the roles of various medium size ant-eating mammals (anteaters, armadillos, pangolins, echidnas, numbats, etc.) found on other continents throughout the Cenozoic, andproboscideans(elephants and their relatives) filled the roles of large herbivores such as hippos, camels, rhinos, and tapirs. Thesireniansdeveloped aquatic body plans and started spreading to other parts of the world by water (evolving convergently with the other groups of marine mammals such ascetaceansandpinnipeds). In addition to their similarity with Laurasian mammals in North America, Europe, and Asia, many afrotheres also exhibit convergent evolution with groups of mammals that evolved and lived exclusively in South America, which was also an island continent for much of the Cenozoic.

The common ancestry of these animals was not recognized until the late 1990s.[1]Historically, thePaenungulatahad been linked to the true ungulates (particularly theperissodactyls); the golden mole, tenrecs, and elephant shrews with the traditional (and polyphyletic/incorrect) taxonInsectivora;and the aardvarks with thepangolinsand thexenarthranswithin the invalid taxonEdentata.Continuing work on the molecular[2][3][4]and morphological[5][6][7][8]diversity of afrotherian mammals has provided ever increasing support for their common ancestry.

Evolutionary relationships

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The afrotherian clade was originally proposed in 1998[1]based on analyses ofDNAsequence data. However, previous studies had hinted at the close interrelationships among subsets of endemic African mammals; some of these studies date to the 1920s[9]and there were sporadic papers in the 1980s[10]and 1990s.[11][12][13]The core of the Afrotheria consists of thePaenungulata,i.e.,elephants,sea cows,andhyraxes,a group with a long history among comparative anatomists.[14][15]Hence, whileDNAsequence data have proven essential to infer the existence of the Afrotheria as a whole, and while theAfroinsectiphilia(insectivoran-grade afrotheres includingtenrecs,golden moles,sengis,andaardvarks) were not recognized as part of Afrotheria without DNA data, some precedent is found in the comparative anatomical literature for the idea that at least part of this group forms aclade.ThePaleocenegenusOcepeia,which is the most completely-known Paleocene African mammal and the oldest afrotherian known from a complete skull, shares similarities with both Paenungulata and Afroinsectiphilia, and may help to characterize the ancestral body type of afrotherians.[16]

Since the 1990s, increasing molecular and anatomical data have been applied to the classification of animals. Both types of data support the idea that afrotherian mammals are descended from a single common ancestor to the exclusion of other mammals. On the anatomical side, features shared by most, if not all, afrotheres include high vertebral counts,[8]aspects ofplacental membrane formation,[17]the shape of the ankle bones,[6][7]the relatively late eruption of the permanent dentition,[18]and undescendedtesticlesremaining in the body near the kidneys.[19]The snout is unusually long and mobile in several Afrotherian species, and this was pointed out as a possible shared-derived character.[20]Studies ofgenomicdata, including millions of alignednucleotidessampled for a growing number of placental mammals, also support Afrotheria as a clade.[21][22]Additionally, there might be some dental synapomorphies uniting afroinsectiphilians, if not afrotheres as a whole: p4 talonid and trigonid of similar breadth, a prominent p4 hypoconid, presence of a P4 metacone and absence of parastyles on M1–2.[7][23]

Afrotheria is now recognized as one of the three major groups within theEutheria(containingplacental mammals).[24]Relations within the three cohorts, Afrotheria,Xenarthra,Boreoeutheria,and the identity of the placental root, remain somewhat controversial.[5]

Afrotheria as a clade has usually been discussed without a Linnaean rank, but has been assigned the rank of cohort, magnorder, and superorder. One reconstruction, which applies themolecular clock,proposes that the oldest split occurred between Afrotheria and the other two some 105 million years ago in themid-Cretaceous,when the African continent was separated from other major land masses.[25]This idea is consistent with the fossil record ofXenarthra,which is restricted to South America (following recent consensus thatEurotamanduais not a xenarthran[26]).

However, Afrotheria itself does not have a fossil record restricted to Africa,[27]and appears in fact to have evolved in the continent's isolation.[28][contradictory][need quotation to verify]More recent, genomic-scale phylogenies favor the hypothesis that Afrotheria and Xenarthra comprise sister taxa at the base of the placental mammal radiation, suggesting an ancientGondwananclade of placental mammals.[29]A 2021 morphological study also proposed to renderMeridiungulatapolyphyletic and recognise most of its clades as part of a group calledSudamericungulata,closely related to hyraxes, whileLitopternaremains a sister taxon toPerissodactyla.[30]

Relations between the various afrotherian orders are still being studied. On the basis of molecular studies, elephants and manatees appear to be related, and likewise elephant shrews and aardvarks.[31]These findings are compatible with the work of earlier anatomists.[14][15]

Phylogeny

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Phylogenetic position of afrotherians (in red) among placentals in a genus-level molecular phylogeny of 116 extant mammals inferred from the gene tree information of 14,509coding DNA sequences.[32]The other major clades are colored:marsupials(magenta),xenarthrans(orange),laurasiatherians(green), andeuarchontoglires(blue).
Afrotheria
A cladogram of Afrotheria based on molecular evidence[15]

Current status and distribution

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Many extant members of Afrotheria appear to have a high risk of extinction (perhaps related to the large size of many). Species loss within this already small group would comprise a particularly great loss of genetic and evolutionary diversity. TheIUCNAfrotheria Specialist Group notes that Afrotheria, as currently reconstructed, includes nearly a third of all mammalian orders currently found in Africa and Madagascar, but only 75 of more than 1,200 mammalian species in those areas.[33]

While most extant species assigned to Afrotheria live in Africa, some (such as the Indian elephant and three of the four sirenian species) occur elsewhere; many of these are also endangered. Prior to theQuaternary extinction event,proboscideans were present on every continent of the world exceptAustraliaandAntarctica.Hyraxes lived in much of Eurasia as recently as the end of thePliocene.The extinct afrotherian orders ofembrithopodsanddesmostylianswere also once widely distributed. However, the desmostylians have recently been viewed as possibleperissodactyls,rather than afrotheres,[34]although this is still controversial;[28]the taxonomic placement of embrithopods is also not clear.[35]

Classification

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Afrotheria is a clade of placental mammals, the stem designation for which isEutheria.Based on precedent, some clades are junior synonyms and arguably should be replaced.[36][37]

See also

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Notes

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  1. ^abStanhope, M. J.; Waddell, V. G.; Madsen, O.; de Jong, W.; Hedges, S. B.; Cleven, G. C.; Kao, D.; Springer, M. S. (1998)."Molecular evidence for multiple origins of Insectivora and for a new order of endemic African insectivore mammals".Proceedings of the National Academy of Sciences.95(17):9967–9972.Bibcode:1998PNAS...95.9967S.doi:10.1073/pnas.95.17.9967.PMC21445.PMID9707584.
  2. ^Springer, Mark S.; Michael J. Stanhope; Ole Madsen; Wilfried W. de Jong (2004)."Molecules consolidate the placental mammal tree"(PDF).Trends in Ecology & Evolution.19(8):430–438.doi:10.1016/j.tree.2004.05.006.PMID16701301.S2CID1508898.
  3. ^Robinson, T. J.; Fu, B.; Ferguson-Smith, M. A.; Yang, F. (2004)."Cross-species chromosome painting in the golden mole and elephant-shrew: support for the mammalian clades Afrotheria and Afroinsectiphillia but not Afroinsectivora".Proceedings of the Royal Society B: Biological Sciences.271(1547):1477–1484.doi:10.1098/rspb.2004.2754.PMC1691750.PMID15306319.
  4. ^Nishihara, H.; Satta, Y.; Nikaido, M.; Thewissen, J.G.M.; Stanhope, M.J.; Okada, N. (2005)."A retroposon analysis of Afrotherian phylogeny".Molecular Biology and Evolution.22(9):1823–1833.doi:10.1093/molbev/msi179.PMID15930154.
  5. ^abAsher RJ, Bennett N, Lehmann T (2009)."The new framework for understanding placental mammal evolution".BioEssays.31(8):853–864.doi:10.1002/bies.200900053.PMID19582725.
  6. ^abcTabuce, R.; Marivaux, L.; Adaci, M.; Bensalah, M.; Hartenberger, J.-L.; Mahboubi, M.; Mebrouk, F.; Tafforeau, P.; Jaeger, J.-J. (2007)."Early Tertiary mammals from North Africa reinforce the molecular Afrotheria clade".Proceedings of the Royal Society B: Biological Sciences.274(1614):1159–1166.doi:10.1098/rspb.2006.0229.PMC2189562.PMID17329227.
  7. ^abcdSeiffert, Erik R (2007)."A new estimate of afrotherian phylogeny based on simultaneous analysis of genomic, morphological, and fossil evidence".BMC Evolutionary Biology.7(1): 224.Bibcode:2007BMCEE...7..224S.doi:10.1186/1471-2148-7-224.PMC2248600.PMID17999766.
  8. ^abSánchez-Villagra, Marcelo R.; Narita, Yuichi; Kuratani, Shigeru (2007). "Thoracolumbar vertebral number: The first skeletal synapomorphy for afrotherian mammals".Systematics and Biodiversity.5(1):1–7.Bibcode:2007SyBio...5Q...1S.doi:10.1017/S1477200006002258.S2CID85675984.
  9. ^Le Gros Clark, W.E. & C.F. Sonntag (1926). "A monograph ofOrycteropus aferIII, the skull, the skeleton of the trunk, and limbs ".Proceedings of the Zoological Society of London.30:445–485.
  10. ^DeJong W.W.; Zweers A.; Goodman M. (1981). "Relationship of aardvark to elephants, hyraxes and sea cows from alpha-crystallin sequences".Nature.292(5823):538–540.Bibcode:1981Natur.292..538D.doi:10.1038/292538a0.PMID7254349.S2CID4256271.
  11. ^DeJong, W.W.; J.A.M. Leunissen & G.J. Wistow (1993). "Eye lens crystallins and the phylogeny of placental orders: evidence for a Macroscelid–Paenungulate clade?". In F. S. Szalay; M. J. Novacek & M.C. McKenna (eds.).Mammal Phylogeny.New York: Springer Verlag. pp.5–12.
  12. ^Porter, Calvin A.; Goodman, Morris; Stanhope, Michael J. (1996)."Evidence on mammalian phylogeny from sequences of Exon 28 of the von Willebrand Factor gene".Molecular Phylogenetics and Evolution.5(1):89–101.Bibcode:1996MolPE...5...89P.doi:10.1006/mpev.1996.0008.PMID8673300.
  13. ^Springer, M. S.; Cleven, Gregory C.; Madsen, Ole; De Jong, Wilfried W.; Waddell, Victor G.; Amrine, Heather M.; Stanhope, Michael J. (1997)."Endemic African mammals shake the phylogenetic tree".Nature.388(6637):61–64.Bibcode:1997Natur.388R..61S.doi:10.1038/40386.hdl:2066/28247.PMID9214502.
  14. ^abSimpson, G. G. (1945). "The principles of classification and a classification of mammals".Bulletin of the American Museum of Natural History.85:1–350.
  15. ^abcTabuce, Rodolphe; Asher, Robert J.; Lehmann, Thomas (2008)."Afrotherian mammals: a review of current data"(PDF).Mammalia.72(1):2–14.doi:10.1515/MAMM.2008.004.S2CID46133294.Archived from the original on 2021-08-01.Retrieved2023-04-30.
  16. ^abGheerbrant, Emmanuel; Amaghzaz, Mbarek; Bouya, Baadi; Goussard, Florent; Letenneur, Charlène (2014)."Ocepeia(Middle Paleocene of Morocco): The Oldest Skull of an Afrotherian Mammal ".PLOS ONE.9(2): e89739.Bibcode:2014PLoSO...989739G.doi:10.1371/journal.pone.0089739.PMC3935939.PMID24587000.
  17. ^Mess, Andrea; Carter, Anthony M. (2006)."Evolutionary transformations of fetal membrane characters in Eutheria with special reference to Afrotheria".Journal of Experimental Zoology Part B: Molecular and Developmental Evolution.306B(2):140–163.Bibcode:2006JEZB..306..140M.doi:10.1002/jez.b.21079.PMID16254985.
  18. ^Asher, Robert J; Lehmann, Thomas (2008)."Dental eruption in afrotherian mammals".BMC Biology.6(1): 14.doi:10.1186/1741-7007-6-14.PMC2292681.PMID18366669.
  19. ^Sharma, Virag; Lehmann, Thomas; Stuckas, Heiko; Funke, Liane; Hiller, Michael (2018)."Loss of RXFP2 and INSL3 genes in Afrotheria shows that testicular descent is the ancestral condition in placental mammals".PLOS Biology.16(6): e2005293.doi:10.1371/journal.pbio.2005293.ISSN1545-7885.PMC6023123.PMID29953435.
  20. ^Hedges, SB (2001)."Afrotheria: Plate tectonics meets genomics".Proc Natl Acad Sci U S A.98(1):1–2.Bibcode:2001PNAS...98....1H.doi:10.1073/pnas.98.1.1.PMC33345.PMID11136239.
  21. ^Murphy, W. J.; Pringle, T. H.; Crider, T. A.; Springer, M. S.; Miller, W. (2007)."Using genomic data to unravel the root of the placental mammal phylogeny".Genome Research.17(4):413–421.doi:10.1101/gr.5918807.PMC1832088.PMID17322288.
  22. ^Nikolaev, Sergey; Montoya-Burgos, Juan I.; Margulies, Elliott H.; NISC Comparative Sequencing Program; Rougemont, Jacques; Nyffeler, Bruno; Antonarakis, Stylianos E. (2007)."Early History of Mammals Is Elucidated with the ENCODE Multiple Species Sequencing Data".PLOS Genetics.3(1): e2.doi:10.1371/journal.pgen.0030002.PMC1761045.PMID17206863.
  23. ^Cote S, Werdelin L, Seiffert ER, Barry JC (March 2007)."Additional material of the enigmatic Early Miocene mammalKelbaand its relationship to the order Ptolemaiida ".Proc Natl Acad Sci USA.104(13):5510–5.Bibcode:2007PNAS..104.5510C.doi:10.1073/pnas.0700441104.PMC1838468.PMID17372202.
  24. ^William J. Murphy; Eduardo Eizirik; Mark S. Springer; et al. (14 December 2001)."Resolution of the Early Placental Mammal Radiation Using Bayesian Phylogenetics"(PDF).Science.294(5550):2348–2351.Bibcode:2001Sci...294.2348M.doi:10.1126/science.1067179.PMID11743200.S2CID34367609.Archived fromthe original(PDF)on 27 March 2016.Retrieved15 May2014.
  25. ^Springer, M. S.; Murphy, W. J.; Eizirik, E.; O'Brien, S. J. (2003)."Placental mammal diversification and the Cretaceous-Tertiary boundary".Proceedings of the National Academy of Sciences.100(3):1056–1061.Bibcode:2003PNAS..100.1056S.doi:10.1073/pnas.0334222100.PMC298725.PMID12552136.
  26. ^Rose KD, Emry RJ, Gaudin TJ, Storch G (2005). "Xenarthra and Pholidota.". In Rose KD, Archibald JD (eds.).The Rise of Placental Mammals: Origins and Relationships of the Major Extant Clades.Baltimore, MD: Johns Hopkins University Press.
  27. ^Zack S.P.; Penkrot T.A.; Bloch J.I.; Rose K.D. (2005)."Affinities of 'hyopsodontids' to elephant shrews and a Holarctic origin of Afrotheria"(PDF).Nature.434(7032):497–501.Bibcode:2005Natur.434..497Z.doi:10.1038/nature03351.PMID15791254.S2CID4428738.
  28. ^abGheerbrant, 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.PMC4934866.PMID27384169.
  29. ^Prasad, A. B.; Allard, M. W.; Green, E. D. (2008)."Confirming the Phylogeny of Mammals by Use of Large Comparative Sequence Data Sets".Molecular Biology and Evolution.25(9):1795–1808.doi:10.1093/molbev/msn104.PMC2515873.PMID18453548.
  30. ^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.ISSN2296-701X.
  31. ^Svartman, M.; Stanyon, R. (2012)."The Chromosomes of Afrotheria and Their Bearing on Mammalian Genome Evolution".Cytogenetic and Genome Research.137(2–4):144–153.doi:10.1159/000341387.PMID22868637.S2CID24353318.
  32. ^Scornavacca C, Belkhir K, Lopez J, Dernat R, Delsuc F, Douzery EJ, Ranwez V (April 2019)."OrthoMaM v10: Scaling-up orthologous coding sequence and exon alignments with more than one hundred mammalian genomes".Molecular Biology and Evolution.36(4):861–862.doi:10.1093/molbev/msz015.PMC6445298.PMID30698751.
  33. ^"What is Afrotheria?".IUCN Afrotheria Specialist Group.Retrieved10 December2013.
  34. ^abCooper, L. N.; Seiffert, E. R.; Clementz, M.; Madar, S. I.; Bajpai, S.; Hussain, S. T.; Thewissen, J. G. M. (2014-10-08)."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.PMC4189980.PMID25295875.
  35. ^Erdal, O.; Antoine, P.-O.; Sen, S.; Smith, A. (2016)."New material ofPalaeoamasia kansui(Embrithopoda, Mammalia) from the Eocene of Turkey and a phylogenetic analysis of Embrithopoda at the species level ".Palaeontology.59(5):631–655.Bibcode:2016Palgy..59..631E.doi:10.1111/pala.12247.S2CID89418652.
  36. ^"Afrosoricida".Mammal Species of the World, 3rd edition.Retrieved17 March2014.
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  38. ^AAnthony Ravel; Maeva Orliac (2014). "The inner ear morphology of the 'condylarthran' Hyopsodus lepidus".Historical Biology.27(8):957–969.doi:10.1080/08912963.2014.915823.S2CID84391276.
  39. ^abAvilla, 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.

References

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