Earth
and Space Sciences Faculty |
|
John
M. Rensberger |
Areas of Interest:
Vertebrate Paleontology
Research Group:
Paleontology
Other
UW Academic Affiliations:
UW Burke Museum
Education:
Ph.D., University of California,
Berkeley, 1967
Background:
John Rensberger received
his Ph.D. in 1967 at the University of California, Berkeley, where he studied
mammalian and lower vertebrate systematic and evolutionary paleontology, chordate
anatomy, paleobotany, invertebrate paleontology and terrestrial and marine biostratigraphy.
As a graduate student he researched fossil insectivore and cetacean systematics
and phyletic relationships, and analyzed the changes in rapidly evolving populations
of late Oligocene geomyoid rodents.
At the University of Washington he continued to study evolution of stratigraphically successive fossil mammalian populations, and the correlation and relationships among populations from different depositional basins. In Rensberger's studies of morphologic change in evolving populations, much of the data came from jaws and teeth, and he became interested in the dietary adaptations and mechanical factors governing selection for new dental structures. An early study pioneered the use of microscopic patterns of wear, an approach that is now commonly used in both anthropology and paleontology to infer differences in dietary behaviors. This research led to a realization that anisotropic responses of tooth enamel as well as dietary behaviors affect the observed patterns of wear in mammalian teeth and that these effects provide part of the selective basis for dental evolution. Much of the present knowledge of the phylogeny of fossil mammals is based on the shapes of teeth. Using quantitative methods to study the effects of chewing movements on food processing, Rensberger found that some common specializations of dental shape in herbivorous mammals are related to chewing mechanics and direction of jaw movement. But it became apparent that other unidentified factors must also govern evolutionary changes in tooth shape. He and a paleontologist in Europe studying dental wear in fossils independently found an unusual pattern of wear in certain large ungulates. In collaboration they pieced together evidence that the microstructure of the enamel in these mammals had responded to selection for increased resistance to dental attrition. This led to a realization that the material strength of dental tissue is a limiting factor in tooth form and chewing effectiveness, and that interpreting the evolution of dietary behaviors in Cenozoic mammals based on dental form must take into account the effects of microstructural characteristics of the materials. Rensberger's research now is focused on the inter-relationships of dental shape, chewing stresses, enamel structure, and the evolution of mammalian dietary behaviors.
Facilities supporting graduate training and research in vertebrate paleontology in the Department of Geological Sciences include the Burke Museum's more than 42,000 fossil vertebrate specimens and a computer database encompassing this collection, a fossil preparation lab, computer facilities for image analysis, finite element analysis and other quantitative methods, a fully equipped darkroom, and a departmental scanning electron microscope.
Selected Publications:
Rensberger, J. M., 1971,
Entoptychine pocket gophers (Mammalia, Geomyoidea) of the early Miocene John
Day Formation, Oregon, Univ. Calif. Publ. Geol. Sci., v. 90, p. 1-208.
Rensberger, J. M., 1973, Pleurolicine rodents (Geomyoidea) of the John Day Formation, Oregon, and their relationships to taxa from the early and middle Miocene, South Dakota, Univ. Calif. Publ. Geol. Sci., v. 102, p. 1-131.
Rensberger, J. M., 1983, Successions of meniscomyine and allomyine rodents in the Oligo-Miocene John Day Formation, Oregon, Univ. Calif. Publ. Geol. Sci., v. 124, p. 1-176.
Rensberger, J. M., Forstén, A., and Fortelius, M., 1984, Functional evolution of the cheek tooth pattern and chewing direction in Tertiary horses, Paleobiology, v. 10, p. 439-452.
Rensberger, J. M., 1988, The transition from insectivory to herbivory in mammalian teeth. In: Teeth Revisited: Proceedings of the VIIth International Symposium on Dental Morphology, Mus. National d'Histoire Naturelle (Paris) Russell, D. E., Santoro, J. P., and Sigogneau-Russell, D., eds., v. 53, p. 355-369.
Rensberger, J. M., 1992, Relationship of chewing stress and enamel microstructure in rhinocerotoid cheek teeth. In: Structure, Function and Evolution of Teeth, Smith, P., Tchernov, E., eds., Freund Publishing House, Ltd., London, Tel Aviv.
Rensberger, J. M. and Pfretzschner, H. U., 1992, Enamel structure in astrapotheres and its functional implications, Scanning Microscopy, v. 6, p. 495-510.
Graduate Research:
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Earth and Space Sciences (Geology, Geophysics, Geological Sciences) University of Washington Johnson Hall 070 • Box 351310 4000 15th Avenue NE • Seattle, WA 98195-1310 Phone 206-543-1190 • Fax 206-543-0489 • Site Info: webmaster@ess.washington.edu • ESS Advising: advising@ess.washington.edu |