"Mesohippus" was slightly larger than "Epihippus", about 610 mm (24 in) at the shoulder. Its back was less arched, and its face, snout, and neck were somewhat longer. It had significantly larger cerebral hemispheres, and had a small, shallow depression on its skull called a fossa, which in modern horses is quite detailed. The fossa serves as a useful marker for identifying an equine fossil's species. "Mesohippus" had six grinding "cheek teeth", with a single premolar in front—a trait all descendant Equidae would retain. "Mesohippus" also had the sharp tooth crests of "Epihippus", improving its ability to grind down tough vegetation.