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
Temporal range: Late Cretaceous - Recent
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Clade: Eutheria
Infraclass: Placentalia
Clade: Epitheria
Orders and Clades

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.

The 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]

Placentalia  

Alternative hypotheses

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

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

References

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  1. ^ O'Leary, M. A.; Bloch, J. I.; Flynn, J. J.; Gaudin, T. J.; Giallombardo, A.; Giannini, N. P.; Goldberg, S. L.; Kraatz, B. P.; Luo, Z.-X.; Meng, J.; Ni, X.; Novacek, M. J.; Perini, F. A.; Randall, Z. S.; Rougier, G. W.; Sargis, E. J.; Silcox, M. T.; Simmons, N. B.; Spaulding, M.; Velazco, P. M.; Weksler, M.; Wible, J. R.; Cirranello, A. L. (2013). "The Placental Mammal Ancestor and the Post-K-Pg Radiation of Placentals". Science. 339 (6120): 662–667. Bibcode:2013Sci...339..662O. doi:10.1126/science.1229237. hdl:11336/7302. ISSN 0036-8075. PMID 23393258. S2CID 206544776.
  2. ^ For example: Springer, M. (2004). "Molecules consolidate the placental mammal tree". Trends in Ecology & Evolution. 19 (8): 430–438. doi:10.1016/j.tree.2004.05.006. PMID 16701301.
  3. ^ Kriegs, Jan Ole; Churakov, Gennady; Kiefmann, Martin; Jordan, Ursula; Brosius, Jürgen; Schmitz, Jürgen (2006). "Retroposed Elements as Archives for the Evolutionary History of Placental Mammals". PLOS Biology. 4 (4): e91. doi:10.1371/journal.pbio.0040091. PMC 1395351. PMID 16515367.
  4. ^ Nishihara, Hidenori; Maruyama, Shigenori; Okada, Norihiro (2009). "Retroposon analysis and recent geological data suggest near-simultaneous divergence of the three superorders of mammals". Proceedings of the National Academy of Sciences. 106 (13): 5235–5240. Bibcode:2009PNAS..106.5235N. doi:10.1073/pnas.0809297106. PMC 2655268. PMID 19286970.
  5. ^ Churakov, Gennady; Kriegs, Jan Ole; Baertsch, Robert; Zemann, Anja; Brosius, Jürgen; Schmitz, Jürgen (2009). "Mosaic retroposon insertion patterns in placental mammals". Genome Research. 19 (5): 868–875. doi:10.1101/gr.090647.108. PMC 2675975. PMID 19261842.
  6. ^ Song, Sen; Liu, Liang; Edwards, Scott V.; Wu, Shaoyuan (2012). "Resolving conflict in eutherian mammal phylogeny using phylogenomics and the multispecies coalescent model". Proceedings of the National Academy of Sciences. 109 (37): 14942–14947. Bibcode:2012PNAS..10914942S. doi:10.1073/pnas.1211733109. PMC 3443116. PMID 22930817.
  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". Molecular Biology and Evolution. 30 (9): 2145–256. doi:10.1093/molbev/mst117. PMC 3748356. PMID 23813979.
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