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Epitheria Temporal range: Late Cretaceous - Recent
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Clade:	Eutheria
Infraclass:	Placentalia
Clade:	Epitheria
Orders and Clades
Superorder Afrotheria: Clade Afroinsectiphilia Clade Paenungulata Magnorder Boreoeutheria: Superorder Laurasiatheria Superorder Euarchontoglires

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. Epitheres are one of the most successful groups of animals.

The monophyly of Epitheria has been challenged by molecular phylogenetic studies. While preliminary analysis of a set of retroposons shared by both Afrotheria, and Boreoeutheria (presence/absence data) supported the Epitheria clade, 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.

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

Alternative hypotheses

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.

References

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.

External links

• Gross, Liza (2006). "Resolving the Family Tree of Placental Mammals". PLOS Biology. 4 (4): e111. doi:10.1371/journal.pbio.0040111. PMC 1395350. PMID 20076552.
• Waddell, P. J.; Kishino, H.; Ota, R. (2001). "A phylogenetic foundation for comparative mammalian genomics". Genome Informatics. 12: 141–154. PMID 11791233. Archived from the original on 2010-04-23.
• Springer, Mark S.; Murphy, William J.; Eizirik, Eduardo; O'Brien, Stephen J. (2003). "Placental mammal diversification and the Cretaceous–Tertiary boundary". Proceedings of the National Academy of Sciences. 100 (3): 1056–1061. Bibcode:2003PNAS..100.1056S. doi:10.1073/pnas.0334222100. PMC 298725. PMID 12552136.
• Wildman, Derek E.; Chen, Caoyi; Erez, Offer; Grossman, Lawrence I.; Goodman, Morris; Romero, Roberto (2006). "Evolution of the mammalian placenta revealed by phylogenetic analysis". Proceedings of the National Academy of Sciences. 103 (9): 3203–3208. Bibcode:2006PNAS..103.3203W. doi:10.1073/pnas.0511344103. PMC 1413940. PMID 16492730.
• Nikolaev, Sergey; Montoya-Burgos, Juan I.; Margulies, Elliott H.; Program, Nisc Comparative Sequencing; Rougemont, Jacques; Nyffeler, Bruno; Antonarakis, Stylianos E. (2007). "Early History of Mammals is Elucidated with the ENCODE Multiple Species Sequencing Data". PLOS Genetics. 3 (1): e2. doi:10.1371/journal.pgen.0030002. PMC 1761045. PMID 17206863. S2CID 1982092.
• 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.

• Obsolete mammal taxa