Jack Sepkoski
（重定向自Sepkoski）
J. John Sepkoski Jr., (July 26, 1948 – May 1, 1999), was a University of Chicago paleontologist. Sepkoski studied the fossil record and the diversity of life on Earth. Sepkoski and David Raup contributed to the knowledge of extinction events. They suggested that the extinction of dinosaurs 66 mya was part of a cycle of mass extinctions that may have occurred every 26 million years.