USING LANDMARK ANALYSIS TO DETERMINE THE RELATIONSHIP BETWEEN SPINOCYRTIA SHELL MORPHOLOGY AND EUSTATIC SEA-LEVEL VARIATION IN THE DEVONIAN

Within the Devonian at least fourteen global transgressive-regressive (T-R) sea-level cycles are known. The relationship between T-R cycles and the geographic range of marine species is well established. During highstands, species ranges expand, and during spans of low sea-level, species ranges contract. In brachiopods, a correlative link between lithofacies change (as a result of sea-level fluctuations) and morphometric shell variation has been observed, with clear distinctions between nearshore and offshore populations. The brachiopod genus Spinocyrtia has been discovered in a variety of sedimentary facies along the shelves of the Eastern Americas Realm (EAR). Geographically, Spinocyrtia has been found ranging from New York to Canada and into Michigan. To quantify species-level morphological variation within Spinocyrtia, this project has utilized digital photography of dorsal and ventral views and two-dimensional landmark analysis. Using this data in conjunction with GPS and stratigraphic information will allow changes in Spinocyrtia morphospace to be specifically attributed to sea-level changes.