Ameridelphia is traditionally a superorder that includes all

marsupial Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a r ...

s living in the

Americas The Americas, sometimes collectively called America, are a landmass comprising the totality of North America and South America.''Webster's New World College Dictionary'', 2010 by Wiley Publishing, Inc., Cleveland, Ohio. When viewed as a sing ...

except for the monito del monte (''Dromiciops''). It is now regarded as a

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

group.

Orders

The orders within this group are listed below: * Order Didelphimorphia (108 species) ** Family Didelphidae: opossums * Order Paucituberculata (7 species) **Family Caenolestidae: shrew opossums

Evolution and phylogenetics

Modern marsupials are now understood to be an originally South American lineage that later reached Australia and diversified there in a massive adaptive radiation. Molecular data, including analysis of retrotransposon insertion sites in the

nuclear DNA Nuclear DNA (nDNA), or nuclear deoxyribonucleic acid, is the DNA contained within each cell nucleus of a eukaryotic organism. It encodes for the majority of the genome in eukaryotes, with mitochondrial DNA and plastid DNA coding for the rest. ...

of a variety of marsupials, and the fossil evidence indicate that Ameridelphia might best be understood as an evolutionary grade. Since Didelphimorphia appears to be the basal marsupial group, it and Paucituberculata do not seem to be closest relatives. Meanwhile, the unranked

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 ...

Eomarsupialia has been proposed as the name for the Australian marsupials ( Australidelphia minus Microbiotheria, of which ''Dromiciops'' is the only survivor), which in all probability derive from a single colonization out of South America via

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...

References

{{- Marsupials Marsupials of North America Marsupials of Central America Marsupials of South America Mammal superorders Early Cretaceous mammals Cretaceous mammals of North America Cretaceous mammals of South America Cenozoic mammals of North America Cenozoic mammals of South America Paraphyletic groups