An extinct order in the class Mammalia, subclass Allotheria, comprising a major group of early mammals, ranging from Late Jurassic to Late Eocene (about 155 to 35 million years ago). The group is best known from North America, Mongolia, and Europe. Most multituberculates were mouselike in size, although the North American Paleocene Taeniolabis was larger, probably closer to the woodchuck (Marmota monax) in its proportions. Multituberculates appear primarily to have been terrestrial creatures, but some were probably arboreal (living in trees) and others fossorial (adapted for digging). The Eocene decline and extinction of multituberculates may reflect competition from small placental mammals, especially primates and rodents.