Named in memory of paleontologist J. John Sepkoski Jr. (1948–1999). His far-reaching work made a major contribution to quantifying the nature of life’s diversity through time. The compilation of a huge database, begun while he was at the University of Rochester and continued at the University of Chicago, enabled researchers to combine mathematical modeling and paleoecology with massive data arrays. Together with his colleague David Raup, Sepkoski developed the theory that catastrophic extinction events have a 26-million-year periodicity. (M 35485) _ _.