Haramiyidans seem to be the earliest known herbivores amongst basal mammals, assuming they're mammals. Their teeth, which are by far the most common remains, resemble those of the multituberculates. The jaw however, based on Haramiyavia, is less derived; "at the level of evolution of Morganucodon and Kuehneotherium, with a groove for ear ossicles on the dentary" (Butler PM, 2000). It’s tempting to infer that this order represents the ancestors of the multis, a group which appears to have… (More on Haramiyida)