Meeting Abstract
In the Late Cretaceous, North America was divided by the Western Interior Seaway (WIS), a shallow epicontinental sea. Native vertebrate life included marine reptiles, fish, and seabirds such as Hesperornis, a flightless avian with a foot-propelled diving lifestyle similar to cormorants. Occupancy modeling predicts occupancy and detection probabilities for the taxa of interest at sampled sites and is used here to understand environmental and biological factors influencing Hesperornis distribution. Campanian WIS vertebrate occurrences and sedimentological data were gathered for the United States and Canada from peer-reviewed literature, museum collections, and online databases. Occurrences consist of taxa found with and without Hesperornis and include known predators and other contemporaries. The statistical modeling software PRESENCE was used to create and evaluate the performance of occupancy models across the WIS with covariates of local faunas and sedimentary rock type for a single season (Campanian) and multiple seasons (early, middle, and late Campanian). Detection probabilities were allowed to vary across lithologies and seasons to model preservational biases. Results showed higher predicted Hesperornis occupancy for sites with chondrichthyans, plioplatecarpine mosasaurs, polycotylid plesiosaurs, and offshore shale-forming environments. Increased occupancy estimates with these taxa may reflect a fauna where predation pressures did not significantly affect Hesperornis biogeography. Regions of intense study and collection and variable preservation of Campanian outcrops likely inflated the preference for mud-rich offshore environments. This research represents one of the first applications of occupancy modeling to marine vertebrates in the WIS.
