from The American Heritage® Dictionary of the English Language, 4th Edition

  • adj. Of or belonging to the infraclass Eutheria, a division of mammals to which all the placental mammals belong.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • adj. belonging or pertaining to the group Eutheria, comprising the mammals more closely related to animals like humans and rodents than to marsupials.
  • n. a eutherian animal.

from The Century Dictionary and Cyclopedia

  • Pertaining to or having characters found in the Eutheria, or placental mammals.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • adj. of or relating to or belonging to the subclass Eutheria
  • n. mammals having a placenta; all mammals except monotremes and marsupials


From New Latin Euthēria, infraclass name : Greek eu-, eu- + Greek thēria, pl. of thērion, wild animal; see treacle.
(American Heritage® Dictionary of the English Language, Fourth Edition)
From Eutheria, from Ancient Greek εὖ (eu, "good, true") + θηρίον (thērion, "beast"). (Wiktionary)



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  • The extant mammals divide into monotremes and Theria. The monotremes are the platypus and echidnas, the Theria are the rest and divide into marsupials and Eutheria, which latter is all of us (aardvarks, horses, bats, humans etc.). The terminology can be multiplied but the important thing is the bifurcating tree: monotremes plus the rest, and the rest are marsupials plus the rest, the eutherians.

    January 28, 2009

  • Being a monotreme, it's a prototherian.

    January 28, 2009

  • Is the platypus eutherian or metatherian? Or neither? I'm very confused.

    January 28, 2009

  • One of my best Scrabble words, built around "H-E-R". Moreover, I was playing with a group of physical anthropologists and all biology-related words got an additional 3X!

    January 2, 2009