Atlantogenata ("born around the

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

") is a proposed magnorder of placental mammals containing the cohorts or superorders

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 ...

and Afrotheria. These groups originated and radiated in the

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

n and

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

n continents, respectively, presumably in the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

. Together with Boreoeutheria, they make up

Placentalia Placental mammals ( infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distingui ...

. The

monophyly In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent comm ...

of this grouping is supported by some genetic evidence. Alternative hypotheses are that Boreoeutheria and Afrotheria combine to form Epitheria (as generally supported by anatomical and other physiological evidence) or that Boreoeutheria and Xenarthra combine to form Exafroplacentalia or Notolegia. Updated analysis of transposable element insertions around the time of divergence strongly supports the fourth hypothesis of a near-concomitant origin (trifurcation) of the three superorders of mammals: Afrotheria, Boreoeutheria, and Xenarthra. Below shows the phylogeny of the extant atlantogenate families.

References

Further reading