Research Interests

My research focuses on understanding the causes of organismal diversity patterns found over geologic time. Extrinsic factors such as climate change play an important role in regulating biodiversity, but the responses of different groups may be mediated by intrinsic factors, such as morphological innovations or constraints, that they inherit through their phylogenetic history. The fossil record provides the only long-term data we have on how organisms have responded to environmental changes, and how those reactions vary from group to group. As such, it is an important tool in understanding and predicting how organisms might respond in similar situations today.
    
Ungulates (hoofed mammals) are an ideal group to use in studies of diversity patterns for two fundamental reasons: many ungulate groups have living representatives, and ungulates have an exceptionally rich Cenozoic fossil record. We can use information from the living animals, such as molecular, physiological, and developmental data, to interpret extinct relatives. Fossil ungulates are morphologically diverse, occupy a wide variety of niches, and show a wide range of body sizes, all factors which play important roles in diversification.
   
My research into ungulate diversity patterns has taken two distinct approaches to these factors, one focusing on morphological evolution and patterns of diversification in a single lineage (Cetartiodactyla), and the other on extrinsic causes of changes in diversity in feeding guilds of ungulates during the Miocene.

Courses Taught

Graduate Students

Awards

2006 - NSERC - University Faculty Award

Selected Publications

• Fraser, D., Mallon, J., Furr, R. S. and J. M. Theodor. In press. Improving the repeatability of Low Magnification Microwear methods using High Dynamic Range Imaging. Palaios.
  
• Theodor, J. M. in press. Micro CT scanning of the ear region of Cainotherium: Character analysis and implications. Journal of Vertebrate Paleontology.
  
• Geisler, J. H. and J. M. Theodor. 2009. Hippopotamus and whale phylogeny. Nature, April 19 2009. DOI 10.1038/nature07776.
  
• Theodor, J. M. and R. S. Furr. 2009. High Dynamic Range Imaging as applied to paleontological specimen photography. Palaeontologia Electronica, 12(1): 30 p. http://palaeo-electronica.org/2009_1/167/index.html
  
• Theodor, J. M., J. Erfurt and G. Métais. 2007. The earliest artiodactyls: Diacodexeidae, Dichobunidae, Homacodontidae, Leptochoeridae and Raoellidae, p. 32-58, In The Evolution of Artiodactyls, D. R. Prothero and S. E. Foss, eds. Johns Hopkins University Press.
  
• Geisler, J. H., J. M. Theodor, M. D. Uhen and S. E. Foss, 2007, Phylogenetic relationship of cetaceans to terrestrial artiodactyls, p. 19-31, In The Evolution of Artiodactyls, D. R. Prothero and S. E. Foss, eds. Johns Hopkins University Press.
  
• Theodor, J. M. and S. Foss. 2005. Deciduous dentitions of Eocene ceobochoerid artiodactyls and cetartiodactyl relationships. Journal of Mammalian Evolution, 12(1/2):161-180.
  
• Theodor, J. M., K. D. Rose and J. Erfurt. 2005. Origin and relationships of Artiodactyla, p. 215-233 In The Rise of Placental Mammals, K. D. Rose and J. D. Archibald, eds. Johns Hopkins University Press.
  
• Van Valkenburgh, B., J. M. Theodor, A. Friscia and T. Rowe. 2004. Respiratory turbinates of canids and felids: a quantitative comparison. Journal of Zoology, 264(3):281-293.
• Janis, C. M., J. Damuth and J. M. Theodor. 2004. The species richness of Miocene browsers, and implications for habitat type and primary productivity in the North American grassland biome. Palaeogeography, Palaeoclimatology, Palaeoecology, 207(3-4):371-398.
  
• Theodor, J. M. 2004. Molecular clock divergence estimates and the fossil record of Cetartiodactyla. Journal of Paleontology, 78(1):39-44.
  
• Janis, C. M. J. M. Theodor and B. Boisvert. 2002. Locomotor evolution in camels revisited: a quantitative analysis of pedal anatomy and the acquisition of the pacing gait. Journal of Vertebrate Paleontology 22(1):110-121.
  
• Janis, C. M., J. Damuth and J. M. Theodor. 2002. The origins and evolution of the North American grassland biome: the story from the hoofed mammals. Palaeogeography, Palaeoclimatology, Palaeoecology 177(1-2):183-189.
  
• Janis, C. M. , J. Damuth, and J. M. Theodor. 2000. Mammalian ungulates and terrestrial primary productivity: where have all the browsers gone? Proceedings of the National Academy of Sciences, 97(14):7899-7904.