OPPORTUNITIES EXIST for Undergraduate and Graduate-level Laboratory Research Projects concerning some aspect of vertebrate morphology/anatomy. Preference is give to project that concern the evolution of the vertebrate skull. Highly motivated students are welcome to apply for course-credit at SDSU. Depending on the amount of time spent in the laboratory (and project content), up to 4-hours of course-credit can be earned towards your degree. The following material is offered to provide background information on the research interests in the lab at the present time.

OVERVIEW of previous research efforts in the lab

Pedersen’s graduate training focused on craniofacial morphogenesis in vertebrates and the importance of soft-tissue integration during skeletogenesis. Of particular interest are the histological and gross anatomical shifts imposed on facial development by the effects of spatial constraint among the various subcomponents of the skull. He has investigated the changes in skull shape in salamander larvae when skull mechanics are altered by cannibalistic behavior (Masters - James Hanken), and described the perinatal development of the orofacial complex in bats (Ph.D. - Patricia Freeman).

Many chiropteran taxa have rebuilt the basic mammalian skull around a highly modified rostrum that functions as a tuned resonator (acoustical horn) during the emission of the echolocative call. Accordingly, the developmental path of these nasal "resonators" has been canalized into a new evolutionary trajectory that is quite different from all other mammals. In nasal-emitting taxa, differential growth of the brain and the pharynx even-tually distorts the skull to align the nasal cavity and nasopharynx with the axis of the body in flight. Conversely, oral-emitting taxa construct the skull around an axis aligned with the oral cavity. Structural changes in the pharynx cascade throughout the other functional spaces in the head (otic, optic, nasal, and oral) and leave the remainder of cranial development to accommodate these newly imposed spatial requirements through the redistribution of all musculoskeletal elements associated with the soft palate and larynx. These patterns of skull growth are taxonomically distinct and form the basis for the current re-evaluation of chiropteran systematics.

Initial post-doctoral publication efforts focused upon the rostrum of Old World leaf-nosed bats (Rhinolophidae) which are characterized by expansive nasal cavities and a short hard palate. Mechanically, this organization of the skull is not optimized for robust masticatory function, instead, it is intimately related to the presence of elaborate resonance chambers within the rostrum and the use of the nasal cavities as an acoustical horn. Stemming from these efforts, my friend and colleague Dr. Rick Adams and I co-edited a book with nine contributing authors: Ontogeny, Evolution, and Functional Ecology in the Chiroptera (Cambridge University Press - 2000). We reestablished the importance of ontogenetic studies and perinatal bat biology in studies of the ecology and evolution of bats. We feel that we stimulated renewed debate on the role of morphogenesis and post-partum growth patterns that drive the evolutionary and ecological diversity in vertebrates, with bats as our model system.