Multituberculates are an ancient form of crown-group mammals that evolved in the Triassic and spread across the world in a number of ground-dwelling and arboreal forms, as "the rodents of the Mesozoic".  Although they are often classified as a broad group of mammals along with the monotremes and therians, multies possess a unique anatomy that separates them from all other mammals.  Multituberculates are named for their teeth, which do not form grinding molars as in other mammals, but instead grow in parallel tracks, like the teeth of a comb.  Multies do not grind their food with these teeth, but shear it back and forth with a truly bizarre group of facial muscles.  They also do not gnaw with incisors in the upper jaw, as do rodents, but with a pair of teeth in the lower jaw.

    During the Tertiary, the multituberculates waned in power, offering drastic reductions in diversity in North America and disappearing completely in Asia.  While once the multies occupied virtually all of Laurasia's rodent-like niches, they are now confined entirely to a single clade, Neoptilodontidae.

    These squirrle-like arboreal herbivores of North America and some of South America are the last remaining multituberculates.  They are warm-blooded, fur-covered, and give birth to live young, but like monotremes neoptilodonts lack nipples and dribble milk from patches of modified skin.  Multies are also known regurgitate food into the mouths of their tiny offspring in the same manner as birds.  Neoptilodonts possess flexible ankle joints that allow them to turn their feet backward while climbing trees, and their semi-sprawling posture gives them an almost lizard-like appearance.  These multies lack prehensile tails, and are not as agile as primates, but they are superb nut-crackers, bringing their sharp lower teeth to bear and pulverizing all but the toughest seed-casings.

    Some neoptilodoont species (in the southern part of their range) are fruit-eaters, and have formed a closely-knit symbiotic relationship with fig trees (genus p-Ficus), which has spread the trees across much of North America and assured this weird group of mammals their immortality.

(Text by Daniel Bensen)


Works Referenced:
Toby White's Multituberculate Notes

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