placentalia

Information about placentalia

Placental mammals/Eutheria
Fossil range: Middle Cretaceous - Recent
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House Mouse, Mus musculus

House Mouse, Mus musculus
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Mammalia
Subclass:Theria
Infraclass:Eutheria
Orders[1]
Eutheria[2] is a taxon containing the placental mammals, such as humans. The sister group of Eutheria is Metatheria, which includes marsupials and their extinct relatives.

The name Eutheria comes from the Greek words eu- "well-developed" and ther "beast". When Eutheria was introduced by Thomas Henry Huxley in 1880, he meant for it to be more broad in definition than its precursor Placentalia. Some use Eutheria as a total group which includes the crown group Placentalia and extinct mammals which are closer to Placentalia than to Marsupialia.

Nevertheless, all living Eutherians are placental mammals. This means that a Eutherian fetus is nourished during gestation by a placenta. Eutherians are also viviparous, meaning that the offspring are carried in the mother's uterus until fully developed.

Because of this, Eutherians are different from other mammal groups such as monotremes and marsupials which are not placental. Monotremes, for instance, lay eggs which protect developing young until they are fully developed. Marsupials give birth to partially-developed young who then migrate to a special pouch in the mother's body in which the young continue their development. (Some exceptions do exist. Bandicoots for instance, which are marsupials, develop small placenta-like structures during gestation.)

The earliest known eutherian species is the extinct Eomaia scansoria from the Lower Cretaceous of China. It is a member of Eutheria, but the hips of the animal were too narrowly built to have allowed the birth of well-developed young. Thus it is unlikely that a placenta greatly contributed to the development of Eomaia scansoria's young before they were born.

Members of Eutheria are found on all continents and in all oceans.

See also

Compare and contrast

Notes and references

1. ^ Eutheria phylogeny. Mikko's Phylogeny Archive. Retrieved on 2006-03-08.
2. ^ Today Placentalia and Eutheria are sometimes considered to be the same group. But there are proposals of classification (McKenna & Bell, 1997) that differentiate between the two groups.


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Extant mammal orders by subclass
The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i.e. from 145.5 ± 4.0 million years ago (Ma)) to the beginning of the Paleocene epoch of the Tertiary Period (about 65.5 ± 0.3 Ma).
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M. musculus

Binomial name
Mus musculus
Linnaeus, 1758

The common House Mouse (Mus musculus) is one of the most numerous species of the genus Mus
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Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. Scientific classification also can be called scientific taxonomy, but should be distinguished from folk taxonomy, which lacks scientific basis.
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Chordata
Bateson, 1885

Typical Classes

See below

Chordates (phylum Chordata) are a group of animals that includes the vertebrates, together with several closely related invertebrates.
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Mammalia
Linnaeus, 1758

Subclasses & Infraclasses
  • Subclass †Allotheria*
  • Subclass Prototheria
  • Subclass Theria

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Eomaia

Species: E. scansoria

Binomial name
Eomaia scansoria
Ji et al.
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Maelestes
Wible et al., 2007

Species: M. gobiensis

Binomial name
Maelestes gobiensis
Wible et al.
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Xenarthra
Cope, 1889

Orders and suborders
  • Order Cingulata
  • Order Pilosa
* Suborder Folivora
* Suborder Vermilingua

See text for more details
The superorder Xenarthra
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Cingulata
Illiger, 1811

Families
  • Pampatheriidae (prehistoric)
  • Glyptodontidae (prehistoric)
  • Dasypodidae


Armadillos are small placental mammals, known for having a bony armor shell.
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Pilosa
Flower, 1883

Suborders

Vermilingua - anteaters
Folivora - sloths

The order Pilosa is a group of placental mammals, extant today only in the Americas. It includes the anteaters and sloths.
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Afrotheria

Orders

See Below
Afrotheria is a clade of mammals with the rank of cohort or superorder, that has been proposed based on DNA analysis.
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Afrosoricida
Stanhope, 1998

Families

 Chrysochloridae
 Tenrecidae
The order Afrosoricida (a Latin-Greek compound name which means "looking like African shrews") contains the golden moles of southern Africa and the tenrecs of Madagascar
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Hyracoidea
Huxley, 1869

Family: Procaviidae
Thomas, 1892

Genera

Procavia
Heterohyrax
Dendrohyrax
A hyrax (from Greek
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Macroscelidea
Butler, 1956

Family: Macroscelididae
Bonaparte, 1838

Genera

Rhynchocyon
Petrodromus
Macroscelides
Elephantulus
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Proboscidea
Illiger, 1811

Groups

†Jozaria
†Anthracobunidae
†Moeritheriidae
Euproboscidea
†Numidotheriidae
†Barytheriidae
†Phiomiidae

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Sirenia
Illiger, 1811

Families

Dugongidae
Trichechidae
†Prorastomidae
†Protosirenidae

For information about the Gothic metal band, see Sirenia (band)


Sirenia
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Euarchontoglires

Orders
  • Glires
  • Rodentia
  • Lagomorpha
  • Euarchonta
  • Dermoptera

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Dermoptera
Illiger, 1811

Family: Cynocephalidae
Simpson, 1945

Genera & Species

Cynocephalus
  • Cynocephalus volans
Galeopterus
  • Galeopterus variegatus

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Lagomorpha
Brandt, 1855

Families

Leporidae
Ochotonidae
Prolagidae (extinct)
The Lagomorphs, order Lagomorpha, are an order of mammals of which there are two families, Leporidae (hares and rabbits), and Ochotonidae (pikas).
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Primates
Linnaeus, 1758

Families
  • 15, See classification
A primate is any member of the biological order Primates, the group that contains all the species commonly related to the lemurs, monkeys, and apes, with the last category
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Rodentia
Bowdich, 1821

Suborders

Sciuromorpha
Castorimorpha
Myomorpha
Anomaluromorpha
Hystricomorpha
Rodentia is an order of mammals also known as rodents
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Scandentia
Wagner, 1855

Families
  • Tupaiidae
  • Ptilocercidae


The treeshrews (or tree shrews) are small mammals native to the tropical forests of Southeast Asia.
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Laurasiatheria

Orders
  • Erinaceomorpha
  • Soricomorpha
  • Chiroptera
  • Cetartiodactyla
  • Cetacea
  • Artiodactyla
  • Perissodactyla

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Carnivora
Bowdich, 1821

Families
  • 17, See classification

The diverse order Carnivora (IPA: /kɑrˈnɪvərə/
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Cetartiodactyla

Orders
  • Order: Cetacea
  • Suborders:
  • Suina
  • Tylopoda
  • Ruminantia
  • Family: Hippopotamidae
Cetartiodactyla
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Erinaceomorpha
Gregory, 1910

Family: Erinaceidae
G. Fischer, 1814

Subfamilies & Genera
  • Erinaceinae
  • Atelerix

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