"Tonouchisaurus" (meaning "Tonouchi lizard") is the informal name given to an as yet undescribed genus of dinosaur from the Early Cretaceous Period. It was a theropod which lived in what is now Mongolia. The suggested "type species", "Tonouchisaurus mongoliensis", was coined by Barsbold in 1994. It was notably small: less than three feet in length, although it may have been an ancestor of Tyrannosaurus rex, judging by the known skeletal elements, which include only limb bones. These limb bones include "a complete didactyl manus and complete pes, as well as other limb bones" (Olshevsky 1996).