Cantius is an early Eocene adapid primate with an exceptionally well known fossil record. Measurements were recorded to describe the size and shape of upper and lower first molars collected from a measured stratigraphic section in the Clarks Fork Basin of Wyoming. Rates of change of size and shape are quantified by calculating evolutionary rates in standard deviation units per generation (haldanes). Temporal scaling of rates shows that change in size was generated by a significantly nonrandom directional process, while change in shape was generated by a significantly nonrandom stabilizing process. Size change in Cantius is interpreted to be the result of weak directional selection, and shape change is interpreted to be the result of strong stabilizing selection.
