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...

Carbohydrates, fats and proteins - dietary sources
A Balanced Diet – Carbohydrates and Fat

Apart from vitamins, the human body also requires high energy sources such as carbohydrates and fats. If you want an ove..

Adaptive Radiation
Adaptive Radiation

The diversification of several new species from a recent ancestral source, each adapted to utilize or occupy a vacant ad..

squirrel
Animal Water Regulation

Animals adapt to their environment in aspects of anatomy, physiology, and behavior. This tutorial will help you understa..

Buttress roots
Roots

This study guide tackles plant roots in greater detail. It delves into the development of plant roots, the root structur..

Physiological Homeostasis
Physiological Homeostasis

Homeostasis is essential to maintain conditions within the tolerable limits. Otherwise, the body will fail to function p..

New Zealand Fauna
New Zealand’s Unique Fauna

Meet some of New Zealand's unique fauna, including endemic insects, frogs, reptiles, birds, and mammals, and investigate..

Related Articles...

No related articles found

See all Related Topics