Project Background
The purpose of this project is to determine what morphological changes characterize the life history (ontogeny) of the Ordovician rhynchonellide brachiopod Hiscobeccus capax. In particular, the main goal of the project is to identify what features of H. capax contribute most strongly to overall shape change throughout the ontogeny of the species. Understanding morphological changes and patterns of shape variation (on both ontogenetic and evolutionary scales) is an important prerequisite for designing meaningful experiments to test hypotheses about organism function. The secondary objective of this analysis is to inform an experimental study of passive flow and suspension feeding function in H. capax based on patterns of fluid circulation observed in 1:1 scale articulated plastic models. Although brachiopods are active suspension feeders, capable of pumping water using a specialized feeding organ (lophophore), the shape and orientation of their shells has an important functional relationship with fluid flow, and consequently has significant influence on their metabolism and feeding efficiency (LaBarbera, 1977). In particular, brachiopod species with shells that function to induce fluid flow over the lophophore are generally thought to have a metabolic advantage over forms that rely more on active pumping of water to obtain food. Shells of H. capax have a globose (strongly biconvex) shape and strong ornamentation pattern that has been common among rhynchonellide brachiopod genera from the Ordovician Period (485 Ma) through to the Recent (Savage et al., 2002). This study will test the hypothesis that changes in shell shape occurring throughout the ontogeny of H. capax are associated with differences in the pattern of passive flow through the shell in the juvenile and adult stages of development.