In their 2001 study, Kielan-Jaworowska and Hurum found that most multituberculates could be referred to two suborders: Plagiaulacida and Cimolodonta.
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Thanks to the well-preserved Ptilodus specimens found in the Bighorn Basin, Wyoming, we know that these multituberculates were able to abduct and adduct their big toes, and thus that their foot mobility was similar to that of modern squirrels, which descend trees head first.
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†Uzbekbaatar Kielan-Jaworowska & Nesov, 1992
It's the most derived member of the order Multituberculata known from that locality, and shared the world with the much larger dinosaurs.
The analysis found eutriconodonts to be more closely related to therian mammals than monotremes were, but more distantly than (paraphyletic) amphitheriids, dryolestids, spalacotheriid "symmetrodonts" and multituberculates were.