Pouched mammals (marsupials) probably originated in North America,
where the opossum (Didelphis) still lives. In early Tertiary times,
they spread to South America and especially to Australia, where their greatest
diversity survives today. On most northern continents, very few marsupials
were able to persist in the face of competition from placental mammals.
However, South America had few placentals during the Tertiary, and Australia
had almost none, and marsupials were able to diversify greatly on those continents.
- Marsupial characteristics:
- Young born in virtual fetal condition; gestation completed in an abdominal pouch
- Epipubic ("marsupial") bones to support pouch
- Extra stylar cusps on outer rim of upper molars; wide stylar shelf
- Inflected angle of lower jaw (to support strong medial pterygoid muscle)
- Bulla made from alisphenoid bone
The opossum as a primitive marsupial.
Marsupials in the Americas
Marsupial diversity in Australia
- Ancestry of Australian marsupials
- Dasyuroidea
- Perameloidea
- Diprotodonta
Illustrations
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