His research: "Currently I am studying two phases of mammalian evolution. One involves a curious primitive mammal found in Early Jurassic fissure fillings in southern Wales. It might be involved in the origin of the docodonts, a group including a recently discovered beaver-like form that cavorted in Jurassic streams. The other project concerns the history and processes involved in the evolution of the mammalian faunas of the western interior of North America after the mass extinction used to mark the end of the Cretaceous."
Burning question: "Was the recovery of mammalian faunas after the end-Cretaceous mass extinction simply a matter of evolutionary radiations of a few locally surviving lineages or did immigration of mammals from other areas play a significant role?"
Fossils that particularly interest him: "Fossil vertebrates from the Late Cretaceous and Early Paleocene of Wyoming, Montana, and adjacent areas. Since the early 1970s our field work has focused on sites in northeastern Montana. These collections now form the most comprehensive samples documenting vertebrate evolution across the Cretaceous/Tertiary boundary."
His path to science: "I became interested in vertebrate paleontology because of my grandfather's dislike of trees. Forsaking an opportunity to settle in forested Oregon, he homesteaded in Goshen Hole, eastern Wyoming, an area with only a few cottonwood trees along the ephemeral streams but extensive and very fossiliferous exposures of the Chadron Formation. There, searches for the blue enamel of titanothere teeth and other fossils caught my interest, and I was hooked."
- Clemens, W.A. 2019. Puercolestes and Betonnia (Cimolestidae, Mammalia) from the early Paleocene (Puercan 3 Interval Zone) of northeastern Montana, U.S.A. PaleoBios, 36 Read it
- Eberle, J.J., W.A. Clemens, P.J. McCarthy, A.R. Fiorillo, G.M. Erickson, and P.S. Druckenmiller. 2019. Northernmost record of the Metatheria: a new Late Cretaceous pediomyid from the North Slope of Alaska. Journal of Systematic Palaeontology Read it
- Sprain,C.J., P.R. Renne, G.P. Wilson and W.A. Clemens. 2014. High-resolution chronostratigraphy of the terrestrial Cretaceous-Paleogene transition and recovery interval in the Hell Creek region, Montana. Bulletin of the Geological Society of America (published on line on 16 September 2014)
- Clemens, W.A. 2017 A pantodont (Mammalia) from the latest Puercan North American Land Mammal Age (earliest Paleocene) of the Western Interior. Historical Biology Read it
- Clemens, W.A. 2015. Prodiacodon crustulum (Leptictidae, Mammalia) from the Tullock Member of the Fort Union Formation, Garfield and McCone Counties, Montana, USA. PaleoBios. 32(1):1-17.