Meeting Abstract
The avian vestibulocerebellum coordinates incoming vestibular information with movements of the head and eyes. It is a spatially and functionally segregated system with medial and lateral cerebellar regions coordinating visual responses to translational and rotational movements, respectively. The lateral region is expressed morphologically as the flocculus—a finger-like extension of the cerebellum projecting between the semicircular canals. The flocculus garners special interest as it is visible on an endocast and exhibits a high degree of size variation among both crown and stem taxa. Such variation raises the possibility that floccular size is correlated with functional and/or behavioral variables that may inform the paleobiology of fossil taxa. Two possibilities have been proposed: (1) floccular variation reflects processing demands of complex flight style, (2) floccular expansion is a response to increasing proprioceptive information generated by the wings. The first hypothesis was rejected in a recent study and we found no evidence to support hypothesis 2. Our data indicate floccular variation is largely explained by body size, and taxa diverging from this general scaling pattern likely do so under the influence of multiple factors. That stated, the semicircular canals and orbit both have strong structural ties with the flocculus that do appear to produce some level of covariation. Establishing morphological relationships between the different components of a sensory network opens considerable space for work in and out of the fossil record.
