Eutheria (; from Greek , 'good, right' and , 'beast'; ) is the

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, ...

consisting of all therian mammals that are more closely related to

placentals 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 distinguishe ...

than to

marsupials Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a po ...

. Eutherians are distinguished from noneutherians by various

phenotypic trait A phenotypic trait, simply trait, or character state is a distinct variant of a phenotypic characteristic of an organism; it may be either inherited or determined environmentally, but typically occurs as a combination of the two.Lawrence, Eleano ...

s of the feet, ankles, jaws and teeth. All extant eutherians lack epipubic bones, which are present in all other living mammals (marsupials and

monotreme Monotremes () are prototherian mammals of the order Monotremata. They are one of the three groups of living mammals, along with placentals (Eutheria), and marsupials (Metatheria). Monotremes are typified by structural differences in their brain ...

s). This allows for expansion of the abdomen during pregnancy. The oldest-known eutherian species is ''

Juramaia sinensis ''Juramaia'' is an extinct genus of very basal eutherian mammal known from the Late Jurassic ( Oxfordian stage) deposits of western Liaoning, China. It is a small shrew-like mammal with a body length of approximately 70–100 mm, making it ...

'', dated at from the early Late Jurassic ( Oxfordian) of China. Eutheria was named in 1872 by

Theodore Gill Theodore Nicholas Gill (March 21, 1837 – September 25, 1914) was an American ichthyologist, mammalogist, malacologist and librarian. Career Born and educated in New York City under private tutors, Gill early showed interest in natural histor ...

; in 1880

Thomas Henry Huxley Thomas Henry Huxley (4 May 1825 – 29 June 1895) was an English biologist and anthropologist specialising in comparative anatomy. He has become known as "Darwin's Bulldog" for his advocacy of Charles Darwin's theory of evolution. The storie ...

defined it to encompass a more broadly defined group than Placentalia.

Characteristics

Cambridge Natural History Mammalia Fig 068

Distinguishing features are: *an enlarged malleolus ("little hammer") at the bottom of the

tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

, the larger of the two shin bones *the joint between the first

metatarsal bone The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the ...

and the entocuneiform bone (the innermost of the three

cuneiform bones There are three cuneiform ("wedge-shaped") bones in the human foot: * the first or medial cuneiform * the second or intermediate cuneiform, also known as the middle cuneiform * the third or lateral cuneiform They are located between the navicu ...

) in the foot is offset farther back than the joint between the second metatarsal and middle cuneiform bones—in metatherians these joints are level with each other *various features of jaws and teeth

Subgroups

* Infraclass:

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 distinguished ...

* ''Clade'': † Tamirtheria ** Order: †

Asioryctitheria Asioryctitheria ("Asian digging beasts") is an extinct order of early eutherians. Skull structure With the exception of '' Prokennalestes'', these advanced forms lacked a Meckelian groove. Furthermore, they were equipped with double-rooted can ...

** Order: † Cimolesta ** Order: †

Leptictida Leptictida (''leptos iktis'' "small/slender weasel") is a possibly paraphyletic extinct order of eutherian mammals. Their classification is contentious: according to cladistic studies, they may be (distantly) related to Euarchontoglires (rodents ...

** Family: †

Zalambdalestidae Zalambdalestidae is a clade of Asian eutherians occurring during the Late Cretaceous. Once classified as Glires, features like epipubic bones and various cranial elements have identified these animals as outside of Placentalia, representing thus ...

* Family: †

Adapisoriculidae Adapisoriculidae is an extinct family of non-placental eutherian mammals present during the Paleogene and possibly the Late Cretaceous. They were once thought to be members of the order Erinaceomorpha, closely related to the hedgehog family (Erin ...

* Family: † Didymoconidae * Family: †

Zhelestidae Zhelestidae is a lineage of extinct eutherian mammals. Occurring in the Late Cretaceous from the Turonian to the Maastrichtian, they were an extremely successful group, with representatives present in Europe, Asia, India (and subsequently in Mad ...

* Genus: †''

Acristatherium ''Acristatherium yanensis'' is an extinct basal eutherian from the Early Cretaceous (early Aptian, about ) Lujiatun Bed of the Yixian Formation. It was described on the basis of a single specimen (holotype) from Beipiao, Liaoning, China, by Yao ...

'' * Genus: †'' Ambolestes'' * Genus: †'' Bobolestes'' * Genus: †'' Cokotherium'' * Genus: †''

Durlstodon ''Durlstodon'' is a genus of extinct mammal from the Early Cretaceous of Southern England. It contains a single species, ''Durlstodon ensomi'', which is known from molars found in the Berriasian Lulworth Formation of Durlston Bay, Dorset, after w ...

'' * Genus: †''

Durlstotherium ''Durlstotherium'' is an extinct genus of mammal from the Early Cretaceous. It contains a single species, ''Durlstotherium newmani''. The type specimen was found in Durlston Bay, Dorset, after which the genus was named. ''D. newmani'' was named a ...

'' * Genus: †'' Endotherium'' * Genus: †''

Eomaia ''Eomaia'' ("dawn mother") is a genus of extinct fossil mammals containing the single species ''Eomaia scansoria'', discovered in rocks that were found in the Yixian Formation, Liaoning Province, China, and dated to the Barremian Age of the Lower ...

''? * Genus: †'' Juramaia'' * Genus: †'' Montanalestes'' * Genus: †'' Murtoilestes'' * Genus: †''

Sinodelphys ''Sinodelphys'' is an extinct eutherian from the Early Cretaceous, estimated to be 125 million years old. It was discovered and described in 2003 in rocks of the Yixian Formation in Liaoning Province, China, by a team of scientists including Zhe ...

''?

Evolutionary history

Eutheria contains several

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

as well as larger groups, many with complicated

taxonomic Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

histories still not fully understood. Members of the

, Cimolesta and

have been previously placed within the outdated placental group Insectivora, while Zhelestids have been considered primitive

ungulate Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, cam ...

s. However, more recent studies have suggested these enigmatic taxa represent stem group eutherians, more basal to Placentalia. The weakly favoured cladogram favours Boreoeuthearia as a basal eutherian clade as sister to the Atlantogenata.

References

{{Taxonbar, from=Q17092469 Mammal taxonomy Oxfordian first appearances Extant Late Jurassic first appearances Taxa described in 1872