Distribution and Tooth Morphoguilds of Mosasaurids (Squamata) of the Campanian Western Interior Seaway with Implications for Controls on Mosasaur Paleobiogeography

Abstract

The Western Interior Seaway (WIS) of North America is well known for its mosasaurid squamate diversity, particularly during the Campanian of the Late Cretaceous. This diversity has historically been examined at a fine scale, with many studies investigating the faunal composition of specific assemblages. Mosasaur tooth morphology has also been extensively studied, with tooth characteristics commonly being used as phylogenetic characters. However, many studies examining mosasaur communities and tooth morphology have been focused on broader spatiotemporal or phylogenetic scales. This study investigates the spatial distribution and morphological disparity of Campanian WIS mosasaurs in relation to potentially limiting biotic and environmental factors as well as the importance of online, collections-based resources for paleontological data. 110 Campanian mosasaur occurrences recorded in online databases were categorized according to taxonomic rank and plotted on paleogeographic maps. Mosasaurines constitute approximately 45% of the total mosasaurid species within the seaway; russellosaurines are less common and halisaurines are scarce. Tooth morphoguilds indicative of feeding adaptations were also assigned to each taxon based on preexisting literature and novel measurements of tooth dimensions. The majority of Campanian WIS mosasaurids are found to belong to the 'Cut' guild. Mosasaurines display the highest amount of tooth disparity, with some guilds having a more spatially limited distribution potentially related to a combination of biotic and environmental factors. Many aspects of mosasaur paleoecology and evolution are still poorly understood; further additions to and expansions of online paleontological databases will help create a more complete picture of mosasaur paleobiogeography within the WIS.