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William Clemens
Curator/Professor Emeritus

William Clemens


Phone: (510) 642-6675

Web page:

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."


Smith, S.M., C.J. Sprain, W.A. Clemens, D.L. Lofgren, P.R. Renne, and G.P. Wilson. 2018. Early mammalian recovery after the end-Cretaceous mass extinction: A high-resolution view from McGuire Creek area, Montana, USA. Bulletin of the Geological Society of America.  Read it

Sprain, C.J., P.R. Renne, W.A. Clemens, and G.P. Wilson. 2018. Calibration of chron C29r: New high-precision geochronologic and paleomagnetic constraints from the Hell Creek region, Montana and their implications for the Cretaceous-Paleocene boundary mass extinction. Bulletin of the Geological Society of America.  Read it

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

Chester, S.G.B., J.I. Bloch, D.M. Boyer, and W.A. Clemens. 2015. Oldest known euarchontan tarsals and affinities of Paleocene Purgatorius to Primates. Proceedings of the National Academy of Sciences. 112:1487-1492.

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.

Clemens, W.A., and J.H. Hartman, 2014, From Tyrannosaurus rex to asteroid impact: Early studies (1901-1980) of the Hell Creek Formation in its type area, in G.P. Wilson, W.A. Clemens, J.R. Horner, and J.H. Hartman, (eds.), Through the End of the Cretaceous in the Type Locality of the Hell Creek Formation in Montana and Adjacent Areas: Geological Society of America Special Paper 503, p. 1-87.

Goodwin, M.B. and J.R. Horner. 2014. Cranial morphology of a juvenile Triceratops skull from the Hell Creek Formation, McCone County Montana, with comments on the fossil record of ontogenetically younger skulls. Pp. 333-347 in G.P. Wilson, W.A. Clemens, J.R. Horner, J.H. Hartman, (eds.), Through the End of the Cretaceous in the Type Locality of the Hell Creek Formation in Montana and Adjacent Areas. Geological Society of America Special Paper 503.

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)  Read it

Wilson, G.P., W.A. Clemens, J.R. Horner, and J.H. Hartman (eds.) 2014. Through the End of the Cretaceous in the Type Locality of the Hell Creek Formation in Montana and Adjacent Areas: Geological Society of America Special Paper 503, p. 392.

Chester, S.G.B., J.I. Bloch, and W.A. Clemens. 2013. First known tarsals of the earliest primate Purgatorius. Program of the 82nd Annual Meeting of the American Association of Physical Anthropologists, p. 97-98.

Clemens, W. A. 2013. Cf. Wortmania from the Early Paleocene of Montana and an evaluation of the fossil record of the initial diversification of the Taeniodonta (Mammalia). Canadian Journal of Earth Sciences, 50: 341-354.

Clemens, W. A., and J. A. Lillegraven. 2013. Interpreting stratigraphic relationships and Laramide structural history of the northeastern margin of the Hanna Basin (Wyoming): Meniscoessus (Mammalia, Multituberculata) exposes its faults. Rocky Mountain Geology. 48: 117-141.

Clemens, W. A., and T. Martin. 2013. Review of the non-tritylodontid synapsids from bone beds in the Rhaetic Sandstone, southern Germany. Pal√§ontologische Zeitschrift.   Read it

Clemens, W.A. 2013. Mammals (Pre-Quaternary)Extinctions of. Pp. 1-9 in S. A. Levin (ed.), Encyclopedia of Biodiversity, second edition, volume 5, Academic Press, Waltham, MA.

Renne, P., C. Sprain, G. Wilson, and W. A. Clemens. 2013. 40Ar/39Ar geochronology of the Lancian-Torrejonian interval, Hell Creek region, Montana. Supplement to online Journal of Vertebrate Paleontology, 33: 197.

Scott, C.S., J.D. Gardner, W.A. Clemens, and R.L. Cifelli. 2013. Richard Carr Fox, Canadian Paleontologist. Canadian Journal of Earth Sciences, 50: v-xi.

Chester, Stephen G. B.; Bloch, Jonathan I.; and Clemens, W. A. 2012. Tarsal morphology of the oldest plesiadapiform Purgatorius indicates arboreality in the earliest primates. Journal of Vertebrate Paleontology, Program and Abstracts, 2012, p. 77.

Clemens, W. A., and Wilson, G. P. 2012. Pattern of immigration of purgatoriids and other eutherians into the northern North American Western Interior. Journal of Vertebrate Paleontology, Program and Abstracts, 2012, p. 80.

Clemens, W.A. 2011. Eoconodon ("Triisodontidae," Mammalia) from the Early Paleocene (Puercan) of northeastern Montana, USA  Read it

Clemens, W.A., New morganucodontans from an Early Jurassic fissure filling in Wales (United Kingdom). Palaeontology, 54:1139-1156.

Hartman, J.H., R.D.Butler, W.A. Clemens, and M. Burton-Kelly. 2011. What's in a name? Barnum Brown's Hell Creek Location and Hell Creek Formation Observations. Geological Society of America, Abstracts with Programs. 43(5):601-602.

Archibald, J.D., W. A. Clemens, K. Padian, T. Rowe, N. Macleod, P. M. Barrett, A. Gale, P. Holroyd, H.-D. Sues, N. C. Arens, J. R. Horner, G. P. Wilson, M. B. Goodwin, C. A. Brochu, D. L. Lofgren, S. H. Hurlbert, J. H. Hartman, D. A. Eberth, P. B. Wignall, P. J. Currie, A. Weil, G. V. R. Prasad, L. Dingus, V. Courtillot, A. Milner, A. Milner, S. Bajpai, D. J. Ward, and A. Sahni. 2010. Cretaceous Extinctions: Multiple Causes. Science. 328: 973

Clemens, W.A., 2010. Were immigrants a significant part of the earliest Paleocene mammalian fauna of the North American Western Interior?, Vertebrata PalAsiatica, 48(4): 285-307.   Read it

Clemens, W.A. 2009. New morganucodontans from Early Jurassic fissure fillings in Wales (UK). Journal of Vertebrate Paleontology. 29 (Supplement to 3):80A.

Clemens, W.A. 2009. Review of The Evolution of Artiodactyls. Edited by D.R. Prothero and S.E. Foss. Johns Hopkins University Press. 2008. 375 pp. Zoological Journal of the Linnean Society. 157:225-226.

Clemens, W.A. 2009. Were Asian immigrants a significant part of the earliest Paleocene mammalian faunas of the North American Western Interior? International Symposium on Terrestrial Paleogene Biota and Stratigraphy of Eastern Asia. Abstracts and Guidebook. Pp. 3-4. Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing.

Clemens, W.A. and G.P. Wilson. 2009. Early Torrejonian mammalian local faunas from northeastern Montana, U.S.A. Pp. 111-158 in L.B. Albright, III (ed.) Papers on Geology, Vertebrate Paleontology, and Biostratigraphy in Honor of Michael O. Woodburne. Museum of Northern Arizona, Bulletin 65.

Clemens, W.A. and J. Hartman. 2009. From T. rex to asteroid impact: Early studies (1901-1980) of the Hell Creek Formation in its type area. North American Paleontology Convention. Cincinnati Museum Center Scientific Contributions. 3:133.

Clemens, W.A. 2008. Review of Amniote Paleobiology: Perspectives on the evolution of Mammals, Birds, and Reptiles. Edited by M.T. Carrano, T.J.Gaudin, R.W. Blob and J.R. Wible. Journal of Mammalian Evolution. 15:281-283.

Goodwin, M.B. and W.A. Clemens. Mesozoic continental vertebrates from the Northwestern Plateau, Ethiopia. International conference on paleoanthropology, paleontology, and archaeology in Ethiopia. Jan. 12-14, 2008. Addis Ababa, Ethiopia. Program with abstracts, pp. 18.

Clemens, W.A. 2007. Early Jurassic allotherians from South Wales (United Kingdom). Fossil Record 10:50-59.

Clemens, W.A. 2007. Eutriconodonta (Triconodonta), McGraw-Hill Encyclopedia of Science and Technology, 10th Edition, p. 728-729. Online McGraw-Hill AccessScience.  Read it

Clemens, W.A., M.B. Goodwin, J.H. Hutchison, C.R. Schaff, C.B. Wood, and M.W. Colbert. 2007. First record of a Jurassic mammal (?"Peramura") from Ethiopia. Acta Palaeontologica Polonica 52(3):433-439.  Read it

Anantharaman, S., G. P. Wilson, D. C. Das Sarma, and W.A. Clemens. 2006. A possible Late Cretaceous "Haramiyidan" from India. Journal of Vertebrate Paleontology 26(2):488-490.

Clemens, W. A. 2006. Ecological diversification of mammals during the Mesozoic, the Age of Dinosaurs. Retrieved December 1, 2006, from McGraw-Hill AccessScience  Read it

Clemens, W. A. 2006. Early Paleocene (Puercan) peradectid marsupials from northeastern Montana, North American Western Interior. Palaeontographica, Abt. A. 277:19-31.

Goodwin, M. B., W. A. Clemens, J. R. Horner, and K. Padian. 2006. The smallest known Triceratops skull: New observations on ceratopsid cranial anatomy and ontogeny. Journal of Vertebrate Paleontology 26(1):103-112.  Read it

Clemens, W.A., and T.E. Williamson. 2005. A new species of Eoconodon (Triisodontidae, Mammalia) from the San Juan Basin, New Mexico. Journal of Vertebrate Paleontology 25(1):208-213.