One hundred and forty-three equid astragali from two stratigraphically separated Miocene faunas from California show significant morphological differences between the two faunas and suggest that astragali may be valuable as stratigraphic indicators. In addition, the isolated astragali are related to equid taxa, which, for the most part, are based upon dental morphology. Two-dimensional studies based upon frequency distribution of selected morphological characteristics, together with topological surfaces formed by the junction of three morphological measurements, are useful analytical tools.