Epitheria

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Epitheria
Temporal range: Late Cretaceous - Recent
European Rabbit
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Theriiformes
Infraclass: Eutheria
Magnorder: Epitheria
Orders and Clades

Epitherians comprise all the placental mammals except the Xenarthra. They are primarily characterized by having a stirrup-shaped stapes in the middle ear, which allows for passage of a blood vessel. This is in contrast to the column-shaped stapes found in marsupials, monotremes, and xenarthrans. They are also characterized by having a shorter fibula relative to the tibia.

Epitheria — like Xenarthra and Afrotheria — originated after the K-Pg boundary 66 million years ago, with the placental diversification occurring within the first hundred thousand years after the K-Pg event and the first modern placental orders began appearing 2–3 millions years later.1 Epitheres are one of the most successful groups of animals.

Monophyly of Epitheria has been challenged by molecular phylogenetic studies.2 While preliminary analysis of a set of retroposons shared by both Afrotheria, and Boreoeutheria (presence/absence data) supported the Epitheria clade,3 more extensive analysis of such transposable element insertions around the time of the divergence of Xenarthra, Afrotheria, and Boreoeutheria strongly support the hypothesis of a near-concomitant origin (trifurcation) of these three superorders of mammals.45

Another analysis suggests that the root of this clade lies between the Atlantogenata and Boreoeutheria.6

Eutheria  

Xenarthra


  Epitheria  

Afrotheria


  Boreoeutheria  

Euarchontoglires



Laurasiatheria





Alternative hypotheses

Alternative hypotheses place either Atlantogenata and Boreoeutheria, or Afrotheria and Exafroplacentalia (Notolegia) at the base of the tree:

Eutheria  
  Boreoeutheria  

Euarchontoglires



Laurasiatheria



  Atlantogenata  

Xenarthra



Afrotheria




Eutheria  

Afrotheria


  Exafroplacentalia  

Xenarthra


  Boreoeutheria  

Euarchontoglires



Laurasiatheria





One Bayesian analysis places the root between Atlantogenata and Boreoeutheria.7

References

  1. ^ O'Leary, MA; Bloch, JI; Flynn, JJ; Gaudin, TJ; Giallombardo, A; Giannini, NP; Goldberg, SL; Kraatz, BP; Luo, ZX; Meng, J; Ni, X: Novacek, MJ; Perini, FA; Randall, ZS; Rougier, GW; Sargis, EJ; Silcox, MT; Simmons, NB; Spaulding, M; Velazco, PM; Weksler, M; Wible, JR; Cirranello, AL (8 February 2013). "The Placental Mammal Ancestor and the Post–K-Pg Radiation of Placentals". Science 339 (6120): 662–7. doi:10.1126/science.1229237. OCLC 827160921. PMID 23393258. Retrieved February 2013. 
  2. ^ For example: Springer, Mark S., Michael J. Stanhope, Ole Madsen, and Wilfried W. de Jong. 2004. Molecules consolidate the placental mammal tree" Trends in Ecology and Evolution 19:430–438.
  3. ^ Kriegs, Jan Ole, Gennady Churakov, Martin Kiefmann, Ursula Jordan, Juergen Brosius, and Juergen Schmitz. (2006) Retroposed Elements as archives for the evolutionary history of placental mammals" PLoS Biol 4(4) e91.
  4. ^ Nishihara, H., Maruyama, S. & Okada, N. 2009. Retroposon analysis and recent geological data suggest near-simultaneous divergence of these three superorders of mammals. PNAS 106: 5235-40.
  5. ^ Churakov, G., Kriegs, J.O., Baertsch, R., Zemann, A., Brosius, J. & Schmitz, J. 2009. Mosaic retroposon insertion patterns in placental mammals. Genome Research 19: 868-75.
  6. ^ Song S, Liu L, Edwards SV, Wu S (2012) Resolving conflict in eutherian mammal phylogeny using phylogenomics and the multispecies coalescent model. Proc Natl Acad Sci USA
  7. ^ 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

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