Epitheria

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. ^[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	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:

Placentalia	Atlantogenata Xenarthra Afrotheria Boreoeutheria Euarchontoglires Laurasiatheria

Placentalia	Afrotheria Exafroplacentalia Xenarthra Boreoeutheria Euarchontoglires Laurasiatheria

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

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.