FUNCTIONAL DIVERSITY OF MESOZOIC MARINE PREDATORS IN THE WESTERN TETHYS

During the Mesozoic Marine Revolution, many hard-shelled prey evolved advanced defenses - such as thicker shells - coevolving with changes in the dentition of some marine predators as predators diversified and expanded into new ecological niches. In this study we examine the functional traits of the following marine predators in the phylum Chordata: Actinopterygii and Actinopteri (fish), Chondrichthyes (sharks and rays), Conodonta (jawless “fish”), and Reptilia (crocodiles, turtles, and "saurs"). To understand changes in the functional diversity of marine vertebrates, we examined 394 species across 5 stages (Anisian, Carnian, Bathonian, Aptian, and Maastrichtian) from the western Tethys. Species with similar traits often perform similar ecosystem functions, thus, for each species body size, structural robustness, living habit, motility, degree of attachment, feeding habit, tooth type, hunting style, trophic rank, tiering, and vision to create unique functional groups. Traits were assigned using the literature, modern analogues, morphology (including teeth, jaws, and body), and gut contents. We then examined the following measures of functional diversity for predators across the Mesozoic: Functional Vulnerability (FV), Functional Redundancy (FR), Functional Over Redundancy (FOR), and number of singletons. We observe a strong relationship between the number of species and the number of functions, which declined notably from 8 to 3, and FR, which also declined from 21.6 to 5.3. This coincides with an increase in FV as functional groups were filled with fewer species. Interestingly, we observed an increase in FV and FOR between the Aptian and Maastrichtian where there is a small increase in the number of species. An increase in FOR may arise due to an increase in the number of species without the occupation of new functional space. This appears to be a ‘leveling-out’ of sorts, however, more research into the Aptian and Maastrichtian stages are needed to determine more about this change.