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...

Homeostasis by water regulation
Homeostasis of Organism Water Regulation

Osmoregulation is the regulation of water concentrations in the bloodstream, effectively controlling the amount of water..

Pikas are an indicator species for climate change
Indicator Species and Endangered Species

Certain species are capable of expressing characteristics indicative of the state of the ecosystem they occupy. They are..

Pollution in Freshwater Ecosystems
Pollution in Freshwater Ecosystems

There are many environmental factors that arise due to the usage of water in one way or another and for every action tha..

Psychiatry and mental disorders
Psychiatry & Mental Disorders

Different mental disorders are described here. Read this tutorial to get an overview of schizophrenia, affective mood di..

Birth of a Human Baby
Birth of a Human Baby

Following nine months inside the mother's womb is the birth of the baby. Know the different stages of the birthing proce..

Independent Assortment and Crossing Over
Independent Assortment and Crossing Over

This tutorial describes the independent assortment of chromosomes and crossing over as important events in meiosis. Read..