Lawrence Witmer, Ph.D.

     My research focuses primarily on the evolution of head anatomy in a group of animals known as archosaurs, a group comprised of birds and crocodilians today and, in the past, nonavian dinosaurs, pterosaurs (flying reptiles), and a varied group of early forms.  Among the questions I'm asking are: What are the homologies of cephalic structures among archosaurs and amniotes as a whole?  What do these anatomical structures tell us about the functional morphology of the head and hence the biology (or paleobiology) of the organisms?  To what extent can we reconstruct the soft-tissue attributes of extinct organisms? How can we use this information to place these organisms in their communities and then reconstruct the evolution of these communities?

     These questions are both historical and hierarchical in nature and thus require appropriate approaches integrating anatomy, ontogeny, phylogenetics (cladistics), biomechanics, and paleontology, among others.  The extant sample (birds and crocs) are studied via various anatomical techniques, including clearing-and-staining and serial sectioning; static biomechanical modeling and phylogenetics are commonly employed analytical tools.  Most archosaur clades are extinct, and thus fossils are an important data base in my research.  As fossils tend to preserve bone but not soft tissues, the theory and practice of soft-tissue reconstruction in fossil taxa has been a major focus of mine.  I have given special attention to an unusual anatomical system, namely, pneumatic (air-filled) sinuses, and also to the nose and nasal cavity, examining the role of these systems in patterning skull morphogenesis and in evolution of the skull as a whole.

     Related but somewhat parallel research areas include projects on the origin and early radiation of birds.  Furthermore, the study of the history of life is still very much at the stage of simply documenting the morphology and relationships of extinct organisms.  To this end, I have projects on the alpha-level anatomy and systematics of fossil archosaurs, principally of the carnivorous theropod dinosaurs.

Selected References:

• Witmer, L. M. 2001. Nostril position in dinosaurs and other vertebrates and its significance for nasal function. Science 293:850-853.

• Witmer, L. M. 2001. A nose for all reasons. Natural History 110:64-71.

• Witmer, L. M. 2001. The role of Protoavis in the debate on avian origins. In New Perspectives on the Origin and Evolution of Birds, J. A. Gauthier (ed.), Yale Peabody Museum, New Haven.

• Witmer, L. M. 2000. Science, art, and dinosaurs. Science 290:460-461.

• Witmer, L.M., S.D. Sampson, and N. Solounias.  (1999) The proboscis of tapirs (Tapirus terrestris): a case study in novel narial anatomy. Journal of Zoology 248.

• Witmer, L.M. (1999) The phylogenetic history of paranasal air sinuses. pp. 21-34 In: The Paranasal Sinuses of Higher Primates: Development, Function and Evolution, T. Koppe, H. Nagai, and K. W. Alt (eds.), Quintessence, Chicago.

• Sampson, S.D., L.M. Witmer, C.A. Forster, D.W. Krause, P.M. O'Connor, P. Dodson, and F. Ravoavy.  (1998)   Predatory dinosaur remains from Madagascar: implications for the Cretaceous biogeography of Gondwana. Science 280:1048-1051.