Master's Theses

Department

Geosciences

Degree Name

Master of Science (MS)

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. Mosasaurid diversity has historically been examined at a fine scale, with many studies investigating the faunal composition of specific assemblages; however, studies focusing on mosasaur communities within the Western Interior Seaway during specific Ages are currently lacking. 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, while emphasizing the importance of online, collections-based resources for paleontological data.

One hundred and ten Campanian mosasaur occurrences recorded in online open-access paleontological 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 (Pierce II, Cut, Crush, and Crunch-Cut) indicative of feeding adaptations were also assigned to each taxon based on previous studies and novel measurements of tooth dimensions. While multiple representatives of the major mosasaurid clades present within the Campanian WIS were found to belong to a single morphoguild, all tylosaurines and plioplatecarpines assigned to the identified cutting and piercing guilds respectively. Mosasaurines display the highest amount of tooth disparity, with two of the identified morphoguilds (Crunch-Cut and Crush) made up entirely of mosasaurine taxa. All four guilds are found within large portions of the Western Interior Seaway, with extensive overlap occurring in the central and southern portion of the seaway corridor. The Pierce II guild has the largest range, extending from the southern opening to the high Arctic, whereas the Crush guild has the most limited distribution, being restricted to the southern half of the corridor. This disparity in morphoguild distribution is potentially a result of biases, with the Cut and Crunch-Cut guild ranges possibly being limited due to taphonomic or sampling biases. The restricted distribution of the Crush guild, however, may instead reflect the actual distribution of the taxa within the guild, with environmental factors potentially being a major limiting factor. Mosasaurids occupied a wide variety of ecologies within the Campanian WIS due to niche partitioning based on tooth morphology, body size, and diving ability, although several morphoguilds within the WIS are not filled by the clade and instead may have been filled by other organisms. 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.

Keywords

paleontology, paleobiology, paleoecology, aquatic lizard, marine reptile, resource partitioning

Advisor

Dr. Laura Wilson

Date of Award

Spring 2025

Document Type

Thesis

Rights

© The Author

Download


Share

COinS