Book excerpt: The author describes forty-two fossil taxa recovered during a study of the San Timoteo Badlands that used magnetobiostratigraphy to develop a temporal framework for addressing the tectonic evolution of southern California over the last 6 million years. For the Pliocene, small mammals are an effective means of correlating a magnetostratigraphy to the Geomagnetic Polarity Time Scale when radioisotopic dates are unobtainable.