Epitheria

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Epitheria
Temporal range: Late Cretaceous - Recent
Kaninchen.jpg
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 million 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.[4][5]

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[edit]

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[edit]

  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

External links[edit]