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Modern forms

The multituberculate order has no modern forms; it survived only until the end of the Eocene, mid-Tertiary.

Their Extinction

The multituberculates started to decline suddenly at the beginning of the Tertiary. The reasons for their decline and extinction are unknown, but it could be that multituberculates were outcompeted by placental mammal groups, especially early primates and rodents. The placental mammals were diversifying in the Tertiary, so the decline, at the same time, of the multituberculates would suggest that the placental mammals had some kind of competitive edge over multituberculates.

In placental mammals, the young do most of their development in the womb, which means that when they are born they are less dependent on the mother. It would seem that multituberculate young were very small and little developed at birth, much like marsupials, where most of the development of the young is in the pouch after birth (see Reproduction). The strategy of placental mammals is generally thought to be superior and to have been at the origin of their diversification success. The multituberculate strategy may have been one of the factors which made them competitively inferior to placental mammals.

It has also been suggested that the sprawling posture of multituberculate limbs limited  their endurance for long-term running, another disadvantage compared to placental mammals with an upright posture.

The similarities between rodents and multituberculates, notably in the teeth and skull anatomy, could indicate similar diet so competition for food , but as yet the fossil record of multituberculates and early rodents only allows us to guess at what use each made of the resources in their environment. There is no way of conclusively proving that multituberculates and rodents were in direct competition, exploiting the same environment at the same time, although both groups have been reconstructed as small nocturnal granivores (eating seeds and nuts). 

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Author: Aude Caromel
Last updated: 20/11/06
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