Dictionary > Placentalia

Placentalia

Definition
noun
(taxonomy) A subdivision of the class Mammalia characterized primarily by their fetus being carried in the uterus of the mother and nourished via a placenta until the time of birth
Supplement
The class Mammalia pertains to any of the endothermic vertebrates identifiable by the following characteristics: a neocortex, three middle ear bones, a lower jaw made of a single bone, a hairy body covering, a thoracic diaphragm, a four-chambered heart, and females that are mostly viviparous. This taxonomic class can be subdivided into three: (1) Placentalia (placentals), (2) Monotremata (monotremes), and (3) Marsupialia (marsupials).
The Placentalia is a subdivision of mammals characterized primarily by the fetus being carried in the uterus of the mother. The fetus is nourished via a placenta until such time that the fetus is fully developed to be delivered at birth. The placenta is expelled as well following the birth of the offspring. Apart from the placenta, placentals also have a relatively wide opening at the bottom of the pelvis allowing the birth of a large offpring.1 They also lack epipubic bones that would tend to inhibit the expansion of the abdomen during pregnancy. Most mammals belong to this subdivision.
Scientific classification:

  • Kingdom: Animalia
  • Phylum: Chordata
  • Clade: Synapsida
  • Class: Mammalia
  • Clade: Eutheria
  • Infraclass: Placentalia (Owen, 1837)

Other common name(s):

  • placentals

Compare:

See also:

Reference(s):

1 Weil, A. (April 2002). “Mammalian evolution: Upwards and onwards”. Nature 416 (6883): 798–799. doi:10.1038/416798a.


You will also like...

An artistic depiction of a human embryo
Growth and Development of a Human Baby

Upon fertilization, a zygote forms and develops into an embryo. This tutorial elaborates on the growth and development f..

Lake Wakatipu, New Zealand
New Zealand’s Unique Geographical History

Explore why New Zealand has such unique flora and fauna, and learn why long periods of geographical isolation. This less..

DNA - schematic
Genetic Mutations

This tutorial looks at the mutation at the gene level and the harm it may bring. Learn about single nucleotide polymorph..

Angle Oak Tree
Seed Plants

Seed plants are vascular plants. They differ from the other vascular plants in producing seeds that germinate into a new..

Cells in different stages of meiosis
Meiosis – The Genetics of Reproduction

Meiosis is a form of cell division that creates gametes. It is comprised of two divisions that in the end, the resulting..

Transpiration
Water in Plants

The movement of molecules (specifically, water and solutes) is vital to the understanding of plant processes. This tuto..

Related Articles...

No related articles found

See all Related Topics