University of Calgary

Jessica Madeleine Theodor

  • Associate Professor
  • Ecology & Evolutionary Biology

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.


2006 - NSERC - University Faculty Award

Selected Publications

  • Google Scholar Link
  • Bravo-Cuevas, V. M., N. M. Morales-García, C. R. Barrón-Ortiz, J. M. Theodor, M. A. Cabral-Perdomo, 2017. Canid coprolites from the Late Pleistocene of Hidalgo, Central Mexico: Importance for the carnivore record of North America, Ichnos,
  • Bravo-Cuevas, V. M., J. Priego-Vargas, E. Jiménez-Hidalgo, C. R. Barrón-Ortiz, J. M. Theodor, J. M. Castillo-Cerón, 2015. Feeding ecology of Astrohippus stockii form the Late Hemphillian of central Mexico: stable carbon isotopes analysis and dental wear patterns, Ameghiana 52(2):502-516
  • Rankin, B. † , Fox, J., Barrón-Ortiz, C. R. † ,  Chew, A., Holroyd, P., Ludtke, J. † ,  Yang, X. † , Theodor, J. 2015. The extended Price equation quantifies species selection on mammalian body size across the Palaeocene/Eocene Thermal Maximum, Proc. R. Soc. B 282 (1812), 20151097 doi: 10.1098/rspb.2015.1097
  • Janis, C. M., J. M. Theodor, 2014. Cranial and postcranial morphological data in ruminant phylogenetics. Zitteliana, B 32:15-31.
  • Barrón-Ortiz, C. R. † , J. M. Theodor, J. A. Cabrales, 2014. Dietary resource partitioning in the Late Pleistocene horses from Cedral, north-central Mexico: evidence from the study of dental wear. Revista Mexicana de Ciencias Geologícas 31(2), pp.260–269.
  • Snively, E., A. P. Russell, G. L. Powell, J. M. Theodor, M. J. Ryan, 2014. The role of the neck in the feeding behaviour of the Tyrannosauridae: inference based on kinematics and muscle function of extant avians. Journal Of Zoology, 292(4): 290–303. doi:10.1111/jzo.12109
  • Fraser, D.†  , T. Zybutz†  , E. Lightner, J. M. Theodor, 2014. Ruminant mandibular tooth mesowear: a new scheme for increasing paleoecological sample sizes. Journal Of Zoology, 294(1): 41–48. doi:10.1111/jzo.12149
  • Saarinen, J. J., A. G. Boyer, J. H. Brown, D. P. Costa, S. K. M. Ernest, A. R. Evans, M. Fortelius, J. L. Gittleman, M. J. Hamilton, L. E. Harding, K. Lintulaakso, S. K. Lyons, J. G. Okie, R. M. Sibly, P. R. Stephens, J. M. Theodor, M. D. Uhen, F. A. Smith, 2014. Patterns of maximum body size evolution in Cenozoic land mammals: eco-evolutionary processes and abiotic forcing, Proc R Soc B 281(1784): 20132049–20132049. doi: 10.1098/rspb.2013.2049
  • Okie, J. G., A. G. Boyer, J. H. Brown, D. P. Costa, S. K. M. Ernest, A. R. Evans, M. Fortelius, J. L. Gittleman, M. J. Hamilton, L. E. Harding, K. Lintulaakso, S. K. Lyons, J. J. Saarinen, F. A. Smith, P. R. Stephens, J. Theodor, M. D. Uhen, R. M. Sibly, 2013. Effects of allometry, productivity and lifestyle on rates and limits of body size evolution. Proc R Soc B 280(1764): 20131007–20131007. doi:10.1098/rspb.2013.1007
  • Fraser, D.† , J. M. Theodor, 2013. Ungulate diets reveal patterns of grassland evolution in North America. Palaeogeography Palaeoclimatology Palaeoecology, 369(C), pp.409–421.
  • Evans, A. R., D. Jones, A. G. Boyer, J. H. Brown, D. P. Costa, S. K. M. Ernest, E. M. G. Fitzgerald, M. Fortelius, J. L. Gittleman, M. J. Hamilton, L. E. Harding, K. Lintulaakso, S. K. Lyons, J. G. Okie, J. J. Saarinen, R. M. Sibly, F. A. Smith, P. R. Stephens, J. M. Theodor, M. D. Uhen, 2012. The maximum rate of mammal evolution, PNAS doi:10.1073/pnas.1120774109
    Parham, J., P. Donoghue, C. Bell,T. Calway, J. Head, P.Holroyd, J. Inoue, R. Irmis, W.Joyce, D. Ksepka, J.Patane, N. Smith, J. Tarver, M. van Tuinen, Z. Yang, K. Angielczyk, J. Greenwood, C. Hipsley, L. Jacobs, P. Makovicky, J. Müller, K. Smith, J. Theodor, R. Warnock, M. Benton, 2012. Systematic Biology, 61(2), pp.346–359, doi:10.1093/sysbio/syr107
  • Barrón-Ortiz, C.† , J. M. Theodor, 2011. A Geometric Morphometric Study of North American late Pleistocene equid upper premolars and its potential significance for equid systematics, Current Research in the Pleistocene, 29:147-149.
  • Fraser, D.† ,  J. M. Theodor, 2011. Anterior dentary shape as an indicator of diet in ruminant artiodactyls, Journal of Vertebrate Paleontology, 31:6, 1366-1375, doi:10.1080/02724634.2011.605404
  • Fraser, D.† , J.M. Theodor, 2011. Comparing ungulate dietary proxies using discriminant function analysis. Journal of Morphology, 272:1513–1526, doi:/10.1002/jmor.11001/full
  • Snively, E., J. M. Theodor. 2011. Common functional correlates of head-strike behavior in the pachycephalosaur Stegoceras validum (Ornithischia, Dinosauria) and combative artiodactyls, PLoSOne,,  doi:10.1371/journal.pone.0021422.
  • Smith, F.A., A.G. Boyer, J.H. Brown, D. Costa, T. Dayan, S.K.M. Ernest, A.R. Evans, M. Fortelius, J.L. Gittleman, M. J. Hamilton, L.E. Harding, K. Lintulaakso, S.K. Lyons, C. McCain, J.G. Okie, J.J. Saarinen, R.M. Sibly, P.R. Stephens, J. Theodor, M.D. Uhen, 2010. The Evolution of Maximum Body Size of Terrestrial Mammals. Science, 330:1216-1219, doi:10.1126/science.1194830
  • Fraser, D.† , J. M. Theodor, 2010. The use of gross dental wear in dietary studies of extinct lagomorphs. Journal of Paleontology (4):720-729. doi: 10.1666/09-066.1
  • Theodor, J. M. 2010. Micro-computed tomography scanning of the ear region of Cainotherium: Character analysis and implications. Journal of Vertebrate Paleontology, 29(4):236-243, doi:10.1080/02724630903415979
  • Fraser, D. † , J. Mallon† , R. S. Furr, J. M. Theodor, 2009. Improving the repeatability of low magnification microwear methods using High Dynamic Range Imaging. Palaios, 24:818- 825, doi:10.2110/palo.2009.p09-064r
    Geisler, J. H., J. M. Theodor. 2009. Hippopotamus and whale phylogeny. Nature, April 19 2009. doi:10.1038/nature07776.


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