Editing Birth (section)

===Marsupials===
{{See also|Marsupial#Reproductive system|Marsupial#Early development}}
[[File:Joey in pouch.jpg|thumb|A [[kangaroo]] joey firmly attached to a nipple inside the pouch]]
An infant [[marsupial]] is born in a very immature state.<ref name="Tyndale-BiscoeRenfree1987">{{cite book|author1=Hugh Tyndale-Biscoe|author2=Marilyn Renfree|title=Reproductive Physiology of Marsupials|url=https://books.google.com/books?id=HpjovN0vXW4C&q=birth|date=30 January 1987|publisher=Cambridge University Press|isbn=978-0-521-33792-2}}</ref> The gestation period is usually shorter than the intervals between oestrus periods. The first sign that a birth is imminent is the mother cleaning out her [[Pouch (marsupial)|pouch]]. When it is born, the infant is pink, blind, furless and a few centimetres long. It has nostrils in order to breathe and forelegs to cling onto its mother's hairs but its hind legs are undeveloped. It crawls through its mother's fur and makes its way into the pouch. Here it fixes onto a teat which swells inside its mouth. It stays attached to the teat for several months until it is sufficiently developed to emerge.<ref>{{cite web |url=http://www.naturalworlds.org/thylacine/biology/reproduction/reproduction_5.htm |title=Reproduction and development |publisher=Thylacine Museum |access-date=2013-08-28 |archive-date=2017-06-21 |archive-url=https://web.archive.org/web/20170621040826/http://www.naturalworlds.org/thylacine/biology/reproduction/reproduction_5.htm |url-status=live }}</ref> Joeys are born with "oral shields"; in species without pouches or with rudimentary pouches these are more developed than in forms with well-developed pouches, implying a role in maintaining the young attached to the mother's nipple.<ref>{{cite journal | author = Yvette Schneider Nanette | date = Aug 2011 | title = The development of the olfactory organs in newly hatched monotremes and neonate marsupials | journal = J. Anat. | volume = 219 | issue = 2| pages = 229–242 | doi = 10.1111/j.1469-7580.2011.01393.x | pmc = 3162242 | pmid=21592102}}</ref>