The tarsi of two genera of early Eocene artiodactyls, Bunophorus and Diacodexis, are described. Both possess only four toes, with digits II and V reduced to the status of dew claws. It is suggested that in some lineages of artiodactyls the evolutionary tendency to reduce digits II and V was reversed and that these toes were enlarged, resulting in forms with four fully functional toes by the Oligocene.