Cimolodon tooth

Cimolodon nitidus

Hell Creek Fm., Meade Co., SD, USA
M¹ (1st upper molar)

While you may have mistaken it for a rodent, Cimolodon belonged to a far more ancient and wildly successful group of mammals, the multituberculates (so named for the multiple cusps arranged in rows on their molars). It likely ate seeds and nuts which were handedly ground by its lego-shaped molars. Cimolodon had to be wary of the likes of Pectinodon or other small predatory dinosaurs in the Hell Creek ecosystem. Unlike a few other contemporaneous mammals, this cousin of ours did not survive the K-Pg extinction event and perished along with the non-avian dinosaurs.