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Boreoeutheria (synonymous with Boreotheria) (Greek: βόρειο "north" + ευ "good" + θεριό "beast") is a clade (magnorder) of placental mammals that is composed of the sister taxa Laurasiatheria (most hoofed mammals, most pawed carnivores, and several other groups) and Euarchontoglires (Supraprimates). It is now well supported by DNA sequence analyses, as well as retrotransposon presence or absence data.[citation needed]

Boreoeutheria
Temporal range: Early Paleocene - Holocene, 65–0 Ma
Talpa europaea MHNT.jpg
European mole (Talpa europaea)
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Clade: Exafroplacentalia
Magnorder: Boreoeutheria
Subgroups

The earliest known fossils belonging to this group date to about 65 million years ago, shortly after the K-Pg extinction event, though molecular data suggest they may have originated earlier, during the Cretaceous period.[1]

With the exceptions of moles, hedgehogs, pangolins, some seals and walruses, rhinoceroses, tapirs, hippopotamuses and cetaceans, male members of the clade share the distinction of external testicles which serve the function of cooling the testicles.[2][3]

Contents

Boreoeutherian ancestorEdit

The common ancestor of Boreoeutheria lived between 100 and 80 million years ago. The boreoeutherian ancestor gave rise to species as diverse as giraffes, dogs, mice, bats, whales, and humans. The concept of boreoeutherian ancestor was first proposed in 2004 in the journal Genome Research.[4][5] The paper’s authors claimed that the genome sequence of the boreoeutherian ancestor could be computationally predicted with 98% accuracy, but would “take a few years and a lot of money”. It is estimated to contain three billion base pairs.[4]

ClassificationEdit

Class Mammalia

CladogramEdit

The weakly favoured cladogram favours Boreoeuthearia as a basal Eutherian clade as sister to the Atlantogenata.[6][7]

Eutheria  
  Atlantogenata  

Xenarthra



Afrotheria



  Boreoeutheria  
   

Laurasiatheria


   

Euarchontoglires




NotesEdit

While it is agreed that the cetaceans evolved within artiodactyls, much of the branching order within Laurasiatheria is not yet well resolved. In particular, the most difficult order to place definitively has been and still is Perissodactyla: Their placement within Zooamata is controversial.

One study has suggested that the carnivores, cetaceans, chiroptera and ungulates form an ancient clade.[8] This is supported by another study that suggests that Eulipotyphla are the earliest diverging clade within the Laurasiatheria.[9]

ReferencesEdit

  1. ^ O'Leary, M. A.; Bloch, J. I.; Flynn, J. J.; Gaudin, T. J.; Giallombardo, A.; Giannini, N. P.; Cirranello, A. L. (2013). "The placental mammal ancestor and the post–K-Pg radiation of placentals". Science. 339 (6120): 662–667. doi:10.1126/science.1229237. PMID 23393258. 
  2. ^ D. S. Mills; Jeremy N. Marchant-Forde (2010). The Encyclopedia of Applied Animal Behaviour and Welfare. CABI. pp. 293–. ISBN 978-0-85199-724-7. 
  3. ^ Drew, Liam (8 July 2013). "Why are testicles kept in a vulnerable dangling sac?". slate.com.  "Between these branches, however, is where it gets interesting, for there are numerous groups, our descended but ascrotal cousins, whose testes drop down away from the kidneys but don't exit the abdomen. Almost certainly, these animals evolved from ancestors whose testes were external, which means at some point they backtracked on scrotality, evolving anew gonads inside the abdomen. They are a ragtag bunch including hedgehogs, moles, rhinos and tapirs, hippopotamuses, dolphins and whales, some seals and walruses, and scaly anteaters."
  4. ^ a b John Roach (25 Jan 2005). "Scientists recreate genome of ancient human ancestor". National Geographic. Retrieved 14 Feb 2015. 
  5. ^ Mathieu Blanchette; Eric D. Green; Webb Miller; David Haussler (2004). "Reconstructing large regions of an ancestral mammalian genome in silico". Genome Research. 14: 2412–2423. doi:10.1101/gr.2800104. PMC 534665 . PMID 15574820. Retrieved 14 Feb 2015. 
  6. ^ Foley, Nicole M.; Springer, Mark S.; Teeling, Emma C. (2016-07-19). "Mammal madness: is the mammal tree of life not yet resolved?". Phil. Trans. R. Soc. B. 371 (1699): 20150140. doi:10.1098/rstb.2015.0140. ISSN 0962-8436. PMC 4920340 . PMID 27325836. 
  7. ^ Tarver, James E.; Reis, Mario dos; Mirarab, Siavash; Moran, Raymond J.; Parker, Sean; O’Reilly, Joseph E.; King, Benjamin L.; O’Connell, Mary J.; Asher, Robert J. (2016-02-01). "The Interrelationships of Placental Mammals and the Limits of Phylogenetic Inference". Genome Biology and Evolution. 8 (2): 330–344. doi:10.1093/gbe/evv261. ISSN 1759-6653. PMC 4779606 . PMID 26733575. 
  8. ^ Tsagkogeorga, G; Parker, J; Stupka, E; Cotton, JA; Rossiter, SJ (2013). "Phylogenomic analyses elucidate the evolutionary relationships of bats". Curr Biol. 23: 2262–2267. doi:10.1016/j.cub.2013.09.014. PMID 24184098. 
  9. ^ Morgan, CC; Foster, PG; Webb, AE; Pisani, D; McInerney, JO; O'Connell, MJ (2013). "Heterogeneous models place the root of the placental mammal phylogeny". Mol Biol Evol. 30 (9): 2145–256. doi:10.1093/molbev/mst117. 

Additional referencesEdit

External linksEdit