Sepkoski was born in
Presque Isle, Maine. In 1970, Sepkoski received a B.S. degree,
magna cum laude, from the
University of Notre Dame. Under
Stephen Jay Gould he earned a Ph.D. in geological sciences from
Harvard University in 1977. His Ph.D. was on the field geology and paleontology of the
Black Hills of
South Dakota. From 1974 to 1978, Sepkoski taught at the
University of Rochester. In 1978, he joined the University of Chicago and became a professor in 1986. Sepkoski was also a research associate at the
Field Museum of Natural History in Chicago. He died of heart failure related to
high blood pressure at the age of 50. Sepkoski is perhaps best known for his global compendia of marine animal families and genera, data sets that continue to motivate a tremendous amount of paleobiological research. Sepkoski himself explored his compendium very thoroughly. In 1981, he identified three great
Evolutionary Faunas in the marine animal fossil record. Each of his Evolutionary Faunas, the Cambrian, Paleozoic, and Modern Faunas, is composed of Linnean classes of animals that have covarying diversity patterns, characteristic rates of turnover, and broadly similar ecologies. Most importantly, they sequentially replaced one another as dominant groups during the
Phanerozoic. Sepkoski modeled the Evolutionary Faunas using three coupled
logistic functions, but the underlying drivers of the prominent shift in taxonomic composition represented by the three faunas remains unknown. Sepkoski was married to paleontologist
Christine Janis, a specialist in fossil mammals. His son (from a previous marriage) is the historian of science
David Sepkoski. ==Awards==