Exafroplacentalia or Notolegia is a
clade
In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
of
placental mammals proposed in 2001 on the basis of molecular research.
Exafroplacentalia places
Xenarthra
Xenarthra (; from Ancient Greek ξένος, xénos, "foreign, alien" + ἄρθρον, árthron, "joint") is a superorder and major clade of placental mammals native to the Americas. There are 31 living species: the anteaters, tree sloths, and ...
as a sister group to the
Boreoeutheria
Boreoeutheria (, "northern eutherians") is a magnorder of Placentalia, placental mammals that groups together superorders Euarchontoglires and Laurasiatheria. The clade includes groups as diverse as giraffes, Sus (genus), pigs, zebras, Rhinoceros ...
(comprising
Laurasiatheria
Laurasiatheria (; "Laurasian beasts") is a superorder of Placentalia, placental mammals that groups together true insectivores (eulipotyphlans), bats (chiropterans), carnivorans, pangolins (Pholidota, pholidotes), even-toed ungulates (Artiodacty ...
and
Euarchontoglires),
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").
[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.] Hence, several alternative hypotheses can be considered.
Alternative hypotheses
One alternative hypothesis is the
Epitheria hypothesis:
Another alternative hypothesis is the
Atlantogenata
Atlantogenata ("born around the Atlantic Ocean") is a proposed magnorder of placental mammals containing the cohorts or superorders Xenarthra and Afrotheria. These groups originated and radiated in the South American and African continents, ...
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
Atlantogenata ("born around the Atlantic Ocean") is a proposed magnorder of placental mammals containing the cohorts or superorders Xenarthra and Afrotheria. These groups originated and radiated in the South American and African continents, ...
References
Further reading
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{{Taxonbar, from=Q133342
Obsolete mammal taxa