Editing Placentalia (section)

== Anatomical features ==
Placental mammals are anatomically distinguished from other mammals by:
* a sufficiently wide opening at the bottom of the [[pelvis]] to allow the birth of a large baby relative to the size of the mother.<ref name="Weil2002MammalianEvolution">{{cite journal |author=Weil, A. |title=Mammalian evolution: Upwards and onwards |journal=Nature |volume=416 |pages=798–799 |date=April 2002 |doi=10.1038/416798a |pmid=11976661 |issue=6883|bibcode=2002Natur.416..798W |s2cid=4332049 }}</ref>
* the absence of [[epipubic bone]]s extending forward from the pelvis, which are found in all other mammals.<ref name=Reilly2003>{{cite journal |author1=Reilly, S. M. |author2=White, T. D. |name-list-style=amp |date=January 2003 |title=Hypaxial Motor Patterns and the Function of Epipubic Bones in Primitive Mammals |journal=Science |volume=299 |issue=5605 |pages=400–402 |doi=10.1126/science.1074905 |pmid=12532019 |bibcode=2003Sci...299..400R |s2cid=41470665 }}</ref> (Their function in non-placental mammals is to stiffen the body during locomotion,<ref name=Reilly2003/> but in placentals they would inhibit the expansion of the abdomen during pregnancy.)<ref>{{cite journal |author=Novacek, M. J., Rougier, G. W, Wible, J. R., McKenna, M. C, Dashzeveg, D. and Horovitz, I. |title=Epipubic bones in eutherian mammals from the Late Cretaceous of Mongolia |journal=Nature |volume=389 |pages=483–486 |date=October 1997 |doi=10.1038/39020 |pmid=9333234 |issue=6650|bibcode=1997Natur.389..483N |s2cid=205026882 }}</ref>
* the rearmost bones of the foot fit into a socket formed by the ends of the [[tibia]] and [[fibula]], forming a complete [[mortise and tenon]] upper ankle joint.<ref name="JiLuoYuan2002EarliestEutherian"/>
* the presence of a [[malleolus]] at the bottom of the fibula.<ref name="JiLuoYuan2002EarliestEutherian"/>
* instead of a [[cloaca]]<ref group=lower-alpha>Exceptional adult placentals that retain a cloaca are [[golden moles]], [[tenrec]]s, [[beaver]]s, and some [[shrew]]s.</ref> like monotremes, marsupials and most other [[vertebrate]]s, the [[Genitourinary system|urogenital ducts]] exit through the [[vulva]] or [[penis]] and the [[rectum]] opens as the [[anus]].<ref name="Wake1992">{{cite book|author=Marvalee H. Wake|title=Hyman's Comparative Vertebrate Anatomy|url=https://books.google.com/books?id=VKlWjdOkiMwC&pg=PA583|access-date=6 May 2013|date=15 September 1992|publisher=University of Chicago Press|isbn=978-0-226-87013-7|page=583}}</ref>
* the presence of a [[corpus callosum]] in between the [[cerebral hemisphere]]s.<ref name="Velut">{{cite journal |last1=Velut |first1=S |last2=Destrieux |first2=C |last3=Kakou |first3=M |title=[Morphologic anatomy of the corpus callosum]. |journal=Neuro-Chirurgie |date=May 1998 |volume=44 |issue=1 Suppl |pages=17–30 |pmid=9757322}}</ref>