Pseudotypotherium exiguum was named by Ameghino (1887) [Other specimens originally included in the type series are lost. Revised Diagnosis—Suborbital fossa present but variable in location, size (from small to large), and depth; large infraorbital foramen; lateral borders of the premaxillae parallel in the upper Revised Diagnosis—Suborbital fossa present but variable in location, size (from small to large), and depth; large infraorbital foramen; lateral borders of the premaxillae parallel in the upper.]. Its type specimen is Syntypes: MLP 12-1683, MLP 12-1684, a partial skull (MLP 12-1683 (skull fragment with a partial portion of the zygomatic arches, presence of left and right suborbital fossae, containing both the right and left upp), and it is a 3D body fossil.