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Laurasiatheria is a clade and a Superorder of placental mammals that includes hedgehogs, even-toed ungulates, whales, bats, odd-toed ungulates, pangolins, and carnivorans, among others. The clade originated on the northern supercontinent of Laurasia. Its last common ancestor is supposed to have diversified ca. 76 to 91 million years ago.


Classification and phylogeny


Laurasiatheria was discovered on the basis of the similar gene sequences shared by the mammals belonging to it; no anatomical features have yet been found that unite the group. The Laurasiatheria clade is based on DNA sequence analyses and retrotransposon presence/absence data. The name comes from the theory that these mammals evolved on the supercontinent of Laurasia, after it split from Gondwana when Pangaea broke up. It is a sister group to Euarchontoglires (or Supraprimates) with which it forms the clade Boreoeutheria. Laurasiatheria includes the following extant taxa: * Eulipotyphla, having subsumed: ** Erinaceomorpha: hedgehogs and gymnures (see Erinaceidae) ** the remaining families of Soricomorpha: moles, shrews, solenodons (cosmopolitan distribution) * Chiroptera: bats (cosmopolitan) * Perissodactyla: odd-toed ungulates including horses, tapirs and rhinoceroses * Artiodactyla: even-toed ungulates including camels, pigs, ruminants (giraffes, deer, antelopes, cattle, sheep, goats, etc.), hippopotamuses and cetaceans ** Cetacea: whales, dolphins, and porpoises * Ferae (unranked) containing the orders: ** Pholidota: pangolins ('scaly anteaters') (Africa, South Asia) ** Carnivora: cats, dogs, bears, seals, and others (cosmopolitan) Uncertainty still exists regarding the phylogenetic tree for extant laurasiatherians, primarily due to disagreement about the placement of Chiroptera and Perissodactyla. Based on morphological grounds, Chiroptera had long been classified in the superorder Archonta (e.g. along with treeshrews and the gliding colugos) until genetic research instead showed their kinship with the other laurasiatheres. The studies conflicted in terms of the exact placement of Chiroptera, however, with it being linked most closely to groups such as Eulipotyphla in the Insectiphillia, Two 2013 studies retrieve that chiropterans, carnivorans, and euungulates form a clade, therefore involving that Eulipotyphla might be a basal group to all other Laurasiatheria taxa. Laurasiatheria is also posited to include several extinct orders and superorders. At least some of these are considered wastebasket taxa, historically lumping together several lineages based on superficial attributes and assumed relations to modern mammals. In some cases, these orders have turned out to either be paraphyletic assemblages, or to be composed of mammals now understood not to be laurasiatheres at all. * Meridiungulata (Collagen sequences found in ''Macrauchenia'' and ''Toxodon'' indicate what are now understood to be the sister taxon to perissodactyls) * Condylarthra (paraphyletic in relation to true ungulates, possibly polyphyletic since some forms may be afrotheres or even non-placental eutherians) * Dinocerata (natural clade closely related to perissodactyls and meridiungulates)Burger, Benjamin J., (2015.) "The systematic position of the saber-toothed and horned giants of the Eocene: the Uintatheres (order Dinocerata)", Utah State University Uintah Basin Campus, Vernal, Utah * Mesonychia (natural clade, though several members, such as ''Andrewsarchus'', are now thought to belong in other groups) * Creodonta (potentially polyphyletic)


See also


* Gondwanatheria


References





Further reading


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External links

* {{Taxonbar|from=Q27379 Category:Mammal taxonomy Category:Mammal superorders