Eutheria
Temporal range: Early Cretaceous–Recent
Skeleton of Microtherulum, a basal eutherian from the Early Cretaceous of China
Northern treeshrew (Tupaia belangeri), a placental eutherian from Southeast Asia
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Theria
Clade: Eutheria
Gill, 1872
Subgroups

see text.

Eutheria (from Greek εὐ-, eú- 'good, right' and θηρίον, thēríon 'beast'; lit.'true beasts'), also called Pan-Placentalia, is the clade consisting of placental mammals and all therian mammals that are more closely related to placentals than to marsupials.

Eutherians are distinguished from noneutherians by various phenotypic traits of the feet, ankles, jaws and teeth. All extant eutherians lack epipubic bones, which are present in all other living mammals (marsupials and monotremes). This allows for expansion of the abdomen during pregnancy,[1] though epipubic bones are present in some primitive eutherians.[2] Eutheria was named in 1872 by Theodore Gill; in 1880, Thomas Henry Huxley defined it to encompass a more broadly defined group than Placentalia.[3]

The oldest known unambiguous eutherians are Durlstodon and Durlstotherium from the Berriasian age of the Early Cretaceous in southern England.[4][5] A possible eutherian species Juramaia sinensis has been dated at 161 million years ago from the early Late Jurassic (Oxfordian) of China.[6] However, Sweetman et al. (2017) considered Juramaia as a stem therian instead,[4] and the Late Jurassic dating has been questioned, with King and Beck (2020) suggesting that Juramaia may originate from Early Cretaceous based on tip-dating analyses, which would make it contemporaneous to several other known eutherians.[7]

Characteristics

The entocuneiform bone

Distinguishing features are:

Taxonomy

Eutheria (i.e. Placentalia sensu lato, Pan-Placentalia):[10][11][12][13][14][9][15][16][17][18][19][20][21][22][23][excessive citations]

Notes:

Evolutionary history

Eutheria contains several extinct genera as well as larger groups, many with complicated taxonomic histories still not fully understood. Members of the Adapisoriculidae, Cimolesta and Leptictida have been previously placed within the outdated placental group Insectivora, while zhelestids have been considered primitive ungulates.[31] However, more recent studies have suggested these enigmatic taxa represent stem group eutherians, more basal to Placentalia.[32][33]

The weakly favoured cladogram favours Boreoeutheria as a basal eutherian clade as sister to the Atlantogenata.[34][35][36]

Eutheria  

Phylogeny after Yang & Yang, 2023.[37]

Metatheria

Eutheria

Acristatherium

Microtherulum

Cokotherium

Juramaia

Eomaia

Prokennalestes

Murtoilestes

Montanalestes

Daulestes

Ukhaatherium

Asioryctes

Kennalestes

Zalambdalestes

Aspanlestes

Protungulatum

Eoungulatum

Below is a phylogeny from Gheerbrant & Teodori (2021):[38]

Eutheria

Eomaia

Prokennalestes

Murtoilestes

Bobolestes

Montanalestes

Paranyctoides

Zhelestidae

Sheikhdheilia

Lainodon

Alostera

Eozhelestes

Avitotherium

Parazhelestes

Aspanlestes

Zhelestes

Borisodon

Gallolestes

Eoungulatum

Bulaklestes

Daulestes

Uchkududon

Ecology

Many non-placental eutherians are thought to have been insectivores, as is the case with many primitive mammals.[39] However, the zhelestids are thought to have been herbivorous.[38]

References

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