Reconstructing locomotor patterns from fossils is crucial for understanding the origins of primates and important transitions in various clades.  Recent studies suggest that the structure of the semicircular canals of the inner ear provides evidence about locomotion.  The canals sense rotational head accelerations and drive reflexes essential for normal movement.  Because bony aspects of canal morphology influence canal sensitivity, this system can be studied in osteologic specimens and fossils.  Variation in canal morphology in living and, by inference, extinct primates has been attributed to interspecific differences in locomotor behavior.  However, the manner in which movement selects for canal morphology is debated, and alternative scenarios cannot be tested because there are no actual data about rotational head acceleration in primates.  To refine proposed links between canal morphology and locomotor function, and to resolve conflicting functional interpretations, this study will examine rotation head accelerations in lemurs and lorises exhibiting diverse locomotor behaviors. 

3-dimensional kinematic analyses will be used to characterize rotational head accelerations during locomotion. Kinematic data will be collected at Duke Lemur Center using an Eagle Digital Motion Analysis System and EvaRT 5.0 software (Motion Analysis Corporation, Santa Rosa, CA).  Each subject will be fitted with a cap bearing an array of reflective tracking markers.  Caps will be custom fashioned for each species using nontoxic polymer clay.  Just before each experiment, the cap will be non-invasively applied to the subject’s head using strips of self-adhesive veterinary tape wrapped in a figure-eight bandage fashion.  Kinematic data will then be acquired from overhead cameras while the subject moves about an open room. Subjects will be presented with various supports to facilitate different locomotor behaviors.  These novel data will be used to test hypotheses concerning intraspecific, interspecific, and body-size dependent variation in head accelerations. 

High-resolution CT scans will be acquired from 2 museum-specimen skulls from each of the species in the sample.  Morphologic data derived from these CT scans will be used to model canal sensitivity to rotations in different directions using established methods.  Observed patterns of head rotation will then be compared to predicted patterns of sensitivity to test hypotheses about the relationship between locomotor behavior and canal design.

            This study will illuminate the debated adaptive link between semicircular canal morphology and locomotor head accelerations.  It will advance understanding of locomotor adaptation in extinct primates and will help to define the limits of fossil-canal-based locomotor reconstruction. Moreover, the use of strepsirhines may advantage inferences about locomotor adaptation in early primate taxa.