What are Multituberculates?

Multituberculates are an extinct group of mammals that superficially look like rodents and probably lived in similar ecological niches. They later went extinct when rodents appeared an out-competed them.

Multituberculates have a unique dentition that includes a blade-like lower fourth premolar. Their other molars and premolars possess rows of cusps (which are sometimes worn into ridges), which give the teeth a Lego-block look. It is these cusps (or tubercles) that give multituberculates their name. Their front teeth poke out like rodent incisors do, though they did not seem to continuously grow like the teeth of modern rodents.

Skull of the common multituberculate genus Ptilodus.


The lower teeth of several genera of multituberculates, showing the blade-like fourth premolar.

Multituberculates lack the “tribosphenic” tooth pattern shared by all living mammals (marsupials and placental mammals) except the egg-laying mammals (platypus and spiny anteaters). Because of this, and other features of their skeletons, paleontologists suspect that multituberculates may have been egg-laying mammals. This may be one of the reasons why multituberculates were replaced by the more rapidly reproducing rodents.

SEM image of the type specimen of the multituberculate Fractinus palmorem

SEM image of the type specimen (lower fourth premolar) of  Fractinus palmorem from The Breaks.

Ptilodus gnomus 2

Upper fourth premolar of Ptilodus gnomus from The Breaks.

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