Eutheria
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Skeleton of Microtherulum, a basal eutherian from the Early Cretaceous of China | |
Northern treeshrew (Tupaia belangeri), a placental eutherian from Southeast Asia | |
Scientific 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]
Distinguishing features are:
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:
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 Members of the Adapisoriculidae, Cimolesta and Leptictida have been previously placed within the outdated placental group Insectivora, while zhelestids have been considered primitive ungulates.[31] However, more recent studies have suggested these enigmatic taxa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]
Phylogeny after Yang & Yang, 2023.[37]
Eutheria | |
Below is a phylogeny from Gheerbrant & Teodori (2021):[38]
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]
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Extant mammal orders
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Yinotheria |
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Theria |
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Eutheria |
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