Eutheria is the taxonomical name for the main group of living mammals.
|Eutheria (including placental mammals)|
Temporal range: Lower Cretaceous – Recent
|House Mouse, Mus musculus|
This taxon contains the placental mammals, of which humans are one species.
Eutheria was introduced by Thomas Henry Huxley in 1880. Members of Eutheria are now found on all continents and in all oceans.
The terms 'Eutheria and 'Placental' do not mean quite the same thing. A few early eutherians in the Lower Cretaceous were not placentals. Eomaia is the earliest example.
All living Eutherians are placental mammals. This means that a Eutherian fetus is fed during gestation by a placenta. The offspring of Eutherians are carried in the mother's uterus until fully developed.
Eutherians are different from other mammal groups such as monotremes and marsupials which (like the earliest eutherians) are not placental.
Monotremes, for example, lay eggs which protect the young until they are fully developed. Marsupials give birth to young who are not completely developed. Their young then move to a special pouch in the mother's body to continue their development.
The earliest known eutherian species is the extinct Eomaia scansoria from the Lower Cretaceous in China.
Notes and referencesEdit
- ↑ "Eutheria phylogeny". Mikko's Phylogeny Archive. Archived from the original on 2008-01-28. Retrieved 2006-03-08.
- ↑ The name Eutheria comes from the Greek words eu- "well-developed" and ther "beast".
- ↑ Ji Q; et al. (April 2002). "The earliest known eutherian mammal". Nature. 416 (6883): 816–822. doi:10.1038/416816a. PMID 11976675. S2CID 4330626. Retrieved 2008-09-24.