A Comparison of Placental and Marsupial Evolution

James Duke, Katie Mayer, & Stephen Ulrich

The oldest known ancestor to marsupials (125 million years old)

The oldest known ancestor to placental mammals (125 million years old)

Eomaia scansoria

Marsupial distribution in the late Cretaceous

http://www.scotese.com/images/094.jpg

Current marsupial distribution

Multiple reproductive organs

Short internal gestation period followed by long development in marsupium

Single reproductive organ

Long gestation period

PlacentaWider pelvic

openings

Placentals

Survival association with death during pregnancy

Common birthing problems of placentalsAmniotic membraneAdvantages of shorter gestation period

Brain structureSocialityDevelopmental focusOther, minor

differences

http://brainmind.com/images/CorpusCallosum222.jpg

Australia•Habitat destruction•Introduction of predators by humans

Worldwide•Smaller average body size

Other•Stephen

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• Pickrell, John. (2003).Oldest Marsupial Fossil Found in China: National Geographic News. Retrieved from

• http://news.nationalgeographic.com/news/2003/12/1215_031215_oldestmarsupial.html

• Nowak, Ronald M. (1999). Walker's Book Of Mammals, Sixth Edition. Baltimore and London: Johns Hopkins University Press. p. 5.

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• Tyndale-Biscoe, Hugh. (2005). Life of Marsupials. CSIRO publishing. Retrieved from http://www.publish.csiro.au/samples/LOMsample.pdf.