Exafroplacentalia Explained

Exafroplacentalia or Notolegia is a clade of placental mammals proposed in 2001 on the basis of molecular research.^{[1] [2] [3]}

Exafroplacentalia places Xenarthra as a sister group to the Boreoeutheria (comprising Laurasiatheria and Euarchontoglires),^[4] thus making Afrotheria a primitive group of placental mammals (the group name roughly means "those which are not African placentals").

Classification

However, this classification makes the autapomorphy (character shared only among Exafroplacentalia) dubious: it is hard to classify a group by the absence of a feature (in this case "not coming from Africa").^[5] Hence, several alternative hypotheses can be considered.

Alternative hypotheses

One alternative hypothesis is the Epitheria hypothesis:

Another alternative hypothesis is the Atlantogenata hypothesis:

Updated analysis of transposable element insertions around the time of divergence strongly supports the fourth hypothesis of a near-concomitant origin of the three superorders of mammals:

See also

• Epitheria
• Atlantogenata

Further reading

• Churakov . G.. Kriegs . J. O.. Baertsch . R.. Zemann . A.. Brosius . J. R.. Schmitz . J. R.. 10.1101/gr.090647.108 . Mosaic retroposon insertion patterns in placental mammals . Genome Research. 19 . 5 . 868–875 . 2009 . 19261842. 2675975.
• Nikolaev . Sergey. Montoya-Burgos . Juan I.. Margulies . Elliott H.. NISC Comparative Sequencing Program. Rougemont . Jacques. Nyffeler . Bruno. Antonarakis . Stylianos E.. 10.1371/journal.pgen.0030002 . Early History of Mammals is Elucidated with the ENCODE Multiple Species Sequencing Data . PLoS Genetics. 3 . 1 . e2 . 2007 . 17206863. 1761045. free.
• Springer . Mark S.. Murphy . William J.. Eizirik . Eduardo. O'Brien . Stephen J.. Placental mammal diversification and the Cretaceous–Tertiary boundary . 10.1073/pnas.0334222100 . Proceedings of the National Academy of Sciences. 100 . 3 . 1056–1061 . 2003 . 12552136. 298725. free.
• Wildman . Derek E.. Chen . Caoyi. Erez . Offer. Grossman . Lawrence I.. Goodman . Morris. Romero . Roberto. Evolution of the mammalian placenta revealed by phylogenetic analysis . 10.1073/pnas.0511344103 . Proceedings of the National Academy of Sciences. 103 . 9 . 3203–3208 . 2006 . 16492730. 1413940. free.

Notes and References

1. Waddell . Peter J. . Kishino . Hirohisa . Ota . Rissa . A phylogenetic foundation for comparative mammalian genomics . . 12 . 141–154 . 2001 . 11791233 . 10.11234/gi1990.12.141 . 2015-08-28 . 2019-07-10 . https://web.archive.org/web/20190710063147/https://www.jsbi.org/pdfs/journal1/GIW01/GIW01F15.html . dead .
2. Murphy, W.J., Pringle, T.H., Crider, T.A., Springer, M.S. & Miller, W. 2007. Using genomic data to unravel the root of the placental mammal phylogeny. Genome Research 17, pp.413-421.
3. Kriegs, J.O., Churakov, G., Kiefmann, M., Jordan, U., Brosius, J. & Schmitz, J. 2006. Retroposed elements as archives for the evolutionary history of placental mammals. Plos Biol 4, pp.e91.
4. 10.1111/j.1096-0031.2009.00255.x. Phylogenetic analysis of 73 060 taxa corroborates major eukaryotic groups. 2009. Goloboff . Pablo A.. Catalano . Santiago A.. Mirande . J. Marcos. Szumik . Claudia A.. Arias . J. Salvador. Källersjö . Mari. Farris . James S.. Cladistics. 25. 3. 211–230 . 34879616. free. 11336/78055. free.
5. Nishihara, H., Maruyama, S. & Okada, N. 2009. Retroposon analysis and recent geological data suggest near-simultaneous divergence of the three superorders of placental mammals. PNAS 106: 5235-40.