Marsupial Characteristics

As previously mentioned marsupials belong to the Mammalian Order and therefore share all possess all these defining characteristics, however, in addition, they have the following features:

• 50% have pouches, but the form of this pouch varies with ecology. In kangaroos the pouch's opening is anterior whereas in animals that tend to dig, such as the bandicoot, the pouch opens posteriorly.
• Epipubic bones are present in both sexes whether or not the species has a pouch.
• The uterus and vagina are biphid
• The male's penis is also biphid
• Different numbers of incisors are present on the upper and lower jaws
• Brains are relatively small and not very convoluted
• Reproduction; young are born very small and undeveloped after a short gestation of approximately 8 - 43 days. The forelimbs, however, are very well developed, allowing the youngster to climb towards it's mothers teat, where it is feed milk and remains until it becomes independent enough to leave (the pouch) for short periods of time and then permanently.

Special Characters:

1. Polyprotodont versus diprotodont

This refers to whether the lower incisors are many and equal in size (Polyprotodont) or whether the medial incisor is greatly enlarged (Diprotodont).

 

Polyprotodont	Diprotodont
Lower jaw of Didelphis (Didelphidae) illustrating the multiple, equally sized incisors.	Lower jaw of Caenolestes (Caenolestidae) illustraing the enlarged anterior inciscor and the multiple small posterior ones. Lower jaw of Macropodidae (Macropodidae) illustrating how sometimes a single enlared incisor can be present.

Pictures reproduced from http://www.csus.edu/

2. Polydactyly versus syndactyly

In the polydactyly condition all the digits of the hind foot are free and approximately equal in size, whereas in the syndactyly condition the digits two and three are distinctly smaller and encased in a common sheath of skin.

Polydactylous		Syndactylous
e.g. Didelphidae	e.g. Dasyuridae	e.g. Peramelidae	e.g. Phascolartidae	e.g. Macropodidae

Pictures reproduced from http://www.csus.edu/

3. Tribosphenic Molar

the basic tribosphenic molar (both upper and lower) of a metatherian is distinguishable from that of a eutherian mammal.

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Author: Catrin Roberts
Last updated: 23.11.83
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