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A Comparison of Placental and Marsupial Evolution

A Comparison of Placental and Marsupial Evolution. James Duke, Katie Mayer, & Stephen Ulrich. Placental-Marsupial Divergence. Sinodelphys szalayi. Eomaia scansoria. The oldest known ancestor to marsupials (125 million years old).

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A Comparison of Placental and Marsupial Evolution

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  1. A Comparison of Placental and Marsupial Evolution James Duke, Katie Mayer, & Stephen Ulrich

  2. Placental-Marsupial Divergence Sinodelphys szalayi Eomaia scansoria • The oldest known ancestor to marsupials (125 million years old) • The oldest known ancestor to placental mammals (125 million years old)

  3. Convergent Evolution

  4. Historical Patterns of Distribution Marsupial distribution in the late Cretaceous http://www.scotese.com/images/094.jpg

  5. Current Patterns of Distribution Current marsupial distribution

  6. Current Patterns, cont.

  7. Reproductive Differences Marsupials Placentals • Multiple reproductive organs • Short internal gestation period followed by long development in marsupium • Single reproductive organ • Long gestation period • Placenta • Wider pelvic openings

  8. Benefits of Marsupial Reproduction • Survival association with death during pregnancy • Common birthing problems of placentals • Amniotic membrane • Advantages of shorter gestation period

  9. Other Differences • Brain structure • Sociality • Developmental focus • Other, minor differences http://brainmind.com/images/CorpusCallosum222.jpg

  10. Other Reasons for Marsupial Extinction • Australia • Habitat destruction • Introduction of predators by humans • Worldwide • Smaller average body size • Other • Stephen

  11. References • Lessa, Enrique P. & Richard A. Farina. (1996). Reassessment of extinction patterns among the late Pleistocene mammals of South America. Palaeontology:Vol 39, part 3, 1996, pp 651-662. Retrieved from http://palaeontology.palass-pubs.org/pdf/Vol%2039/Pages%20651-662.pdf. • 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. • Springer, Mark S., John A.W. Kirsh, & Judd A. Case. The Chronicle of Marsupial Evolution: Molecular Evolution and Adaptive Radiation. Edited by Thomas J. Givnish & Kenneth J. Sytsma. 1997. Cambridge, United Kingdom: Cambridge University Press. Retrieved from http://books.google.com/books?hl=en&lr=&id=d06PgBvL5lIC&oi=fnd&pg=PA129&dq=marsupial+evolution&ots=rongh7ew3o&sig=7vNP_mvfqQhuef5HrtEtmuvSiF4#v=onepage&q=marsupial%20evolution&f=false. • Tyndale-Biscoe, Hugh. (2005). Life of Marsupials. CSIRO publishing. Retrieved from http://www.publish.csiro.au/samples/LOMsample.pdf.

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