Atlantogenata is a proposed

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

s containing the cohorts or superorders

Xenarthra Xenarthra (; from Ancient Greek ξένος, xénos, "foreign, alien" + ἄρθρον, árthron, "joint") is a major clade of placental mammals native to the Americas. There are 31 living species: the anteaters, tree sloths, and armadillos. Ex ...

and

Afrotheria Afrotheria ( from Latin ''Afro-'' "of Africa" + ''theria'' "wild beast") is a clade of mammals, the living members of which belong to groups that are either currently living in Africa or of African origin: golden moles, elephant shrews (also know ...

. 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 relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

n and

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

n continents, respectively, presumably in the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

. Together with

Boreoeutheria Boreoeutheria (, "northern true beasts") is a magnorder of placental mammals that groups together superorders Euarchontoglires and Laurasiatheria. With a few exceptionsExceptional clades whose males lack the usual boreoeutherian scrotum are moles ...

, they make up

Eutheria Eutheria (; from Greek , 'good, right' and , 'beast'; ) is the clade consisting of all therian mammals that are more closely related to placentals than to marsupials. Eutherians are distinguished from noneutherians by various phenotypic tra ...

. The

monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...

of this grouping was supported by some genetic evidence. Alternative hypotheses are that Boreoeutheria and Afrotheria combine to form

Epitheria 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 stape ...

(as generally supported by anatomical and other physiological evidence) or that Boreoeutheria and Xenarthra combine to form

Exafroplacentalia Exafroplacentalia or Notolegia is a clade of placental mammals proposed in 2001 on the basis of molecular research. Exafroplacentalia places Xenarthra as a sister group to the Boreoeutheria (comprising Laurasiatheria and Euarchontoglires), thus ...

Notolegia Exafroplacentalia or Notolegia is a clade of placental mammals proposed in 2001 on the basis of molecular research. Exafroplacentalia places Xenarthra as a sister group to the Boreoeutheria (comprising Laurasiatheria and Euarchontoglires), thus ...

. Updated analysis of

transposable element A transposable element (TE, transposon, or jumping gene) is a nucleic acid sequence in DNA that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genetic identity and genome size. Transp ...

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