Jack Sepkoski

Jack Sepkoski identified the Cambrian, Paleozoic, and Modern evolutionary faunas to categorize the distinct phases of marine life diversity in the Phanerozoic era. He detailed these three successive groupings in his highly influential 1981 paper published in the journal "Paleobiology."

It is a massive, comprehensive database of marine fossil families and genera compiled by Sepkoski to track biodiversity over millions of years. First published in 1982 and later expanded, this compendium provided the foundational quantitative data used by paleontologists to study mass extinctions.

In 1984, Sepkoski and his University of Chicago colleague David Raup analyzed Sepkoski's fossil database and detected a statistically periodic pattern in the record of mass extinctions. They famously concluded that major extinction events seemed to occur roughly every 26 million years, a theory that sparked the search for a theoretical companion star to the sun called Nemesis.

His extensive data tables and compendiums were published in academic journals and later incorporated into the Paleobiology Database (PBDB). Many of his original datasets are also archived and available for public research through university repositories and paleontological institutions.