TESTING FOR CONSISTENCY IN MORPHOLOGICAL SHIFTS ACROSS ENVIRONMENTS FOR AMMONITES OF THE WESTERN INTERIOR SEAWAY
Using the biogeographic zones of Kauffman (1984) and a database of Albian and Cenomanian occurrences compiled from the primary literature and the Paleobiology Database, we identified genera whose constituent species include some found within the WIS and some that appear excluded from it. We digitized aperture shape for each species of interest from photographs of museum specimens and published figures and conducted an elliptical Fourier analysis, the results of which were used to generate a morphospace. The morphospace captures the high variation in shell compression and whorl overlap found in ammonites as well as the morphological distinctiveness of most of the genera. We found no evidence of a common directional shift for species present in the WIS compared to those that were not. However, our results suggest a degree of clustering within some genera by biogeographic region as well as predictable morphological shifts with expansion into the seaway when partitioned by mode of life, highlighting the complex relationship between ecology and environmental change.