| William Alvin Clemens, Jr. | |
| Birth Date: | 14 May 1932[1] |
| Birth Place: | Berkeley, California |
| Death Place: | Berkeley, California |
| Fields: | Vertebrate Paleontology, Geology |
| Workplaces: | University of California-Berkeley, University of Kansas-Lawrence |
| Education: | BA, PhD |
| Alma Mater: | University of California, Berkeley |
| Thesis1 Year: | 1960[2] |
| Doctoral Advisor: | Donald E. Savage |
| Known For: | Research on Mesozoic mammals, K-Pg extinction |
William Alvin Clemens Jr. (May 15, 1932 — November 17, 2020)[3] was a paleontologist at the University of California at Berkeley. He was faculty of the Department of Paleontology from 1967, then the Department of Integrative Biology from 1994 to his retirement and curator of the UC Museum of Paleontology. Clemens was also director of the museum (1987–1989) and chair of the Department of Paleontology (1987–1989). He was awarded a Guggenheim Fellowship (1974–75), a U.S. Senior Scientist Award by the Alexander von Humboldt Foundation, the Romer-Simpson Medal (2006),[4] and was made a Fellow of the California Academy of Sciences.
Clemens was born in Berkeley, California. After graduating from Berkeley High School, he attended the University of California, Berkeley, earning a B.A. in paleontology in 1954 and a Ph.D. in 1960. From 1961 to 1967, he served as faculty in the Zoology Department at the University of Kansas and as the curator of higher vertebrates in their Museum of Natural History.[5]
Clemens' research focussed on the evolution of mammals in the Mesozoic Era, both their origin and diversification as well as the microstructure of the early mammalian jaw and teeth. He was also noted for his research into the extinction of the dinosaurs at the Cretaceous–Paleogene boundary (K–Pg or K-T boundary). Clemens supported a view contrary to the more familiar Alvarez hypothesis model of sudden catastrophic extinction precipitated by an asteroid, which was proposed in part by Walter Alvarez, also at the University of California, Berkeley, at the time. Clemens' research in western North America suggests that the dinosaurs were already undergoing gradual extinction prior to the end of the Cretaceous and that other groups of vertebrates were not severely impacted by the event.