EVALUATING FAUNAL PROVINCES AND THEIR RESPONSE TO ENVIRONMENTAL CHANGE IN THE LATE CRETACEOUS WESTERN INTERIOR SEAWAY AND GULF COASTAL PLAIN

The Western Interior Seaway (WIS) and Gulf Coastal Plain (GCP) are characterized by a dense fossil record of a wide variety of marine invertebrate faunas spanning the Late Cretaceous epoch (~ 100 – 66 Ma). Fluctuating sea levels during this time produced shifts in the geometry and area of habitat in marine basins that almost certainly impacted marine life; the specifics of these interactions are still not well-understood. Biotic provinces represent complex relationships between geographic and phylogenetic histories and ecological frameworks. Analyzing the distribution of biotic provinces through time and in relation to major environmental shifts can therefore shed light on aspects of long-term ecological relationships and how these relationships are influenced by the spatiotemporal patterns of biotic and abiotic change on macroevolutionary timescales.

Previous studies have qualitatively compared faunal assemblages across North America in relation to transgressive-regressive events, but no recent studies have analyzed the paleogeographic distribution of marine provinces using recently developed methods that are more quantitative. Network modeling is a little utilized approach to analyzing faunal provinces spatiotemporally that has not yet been applied to the Late Cretaceous invertebrate taxa of the WIS or GCP. This approach differs from more traditional paleobiogeographic methods by quantifying the similarity between faunal compositions across different geographic units that represent the same and different temporal intervals. Using a well-vetted taxonomic database of over 33,000 fossil occurrences from the WIS and the GCP, this study reevaluates marine faunal provinces by analyzing changes in faunal compositions over the Campanian and Maastrichtian stages of the Late Cretaceous using a network modeling approach (EDENetworks). We explore crucial aspects of macroecological patterns within a complex restricted ocean system over geological time scales, just prior to one of the world’s largest mass extinction. As such, results will shed light on fundamental, and generalizable, Earth-life interactions.