ECOLOGICAL EVOLUTION THROUGHOUT TIME - COMPARING THE DIVERSITY OF THE JURASSIC MORRISON FORMATION AND THE MODERN ANALOG SERENGETI FAUNA

The Morrison Formation of the American West represents one of the most diverse ecosystems in the Mesozoic fossil record, with a diverse predator population and equally abundant herbivorous prey. There are several top predators in the Morrison Formation ecosystem, including Allosaurus, Torvosaurus, Ceratosaurus, and Saurophaganax. To better understand how these predators were able to coexist despite the pressures of competitive exclusion, the Morrison Formation was compared to a modern-day analog to test if predator-prey dynamics in a Jurassic-age ecosystem promote diversity. A modern-day ecosystem that has a large concentration of predators for the ecosystem may share patterns with the Morrison Formation that explain how a large source of prey supports predators. The modern-day analog chosen was the Serengeti of Tanzania, as it is recorded to have the largest concentration of apex predators in one ecosystem globally. The Serengeti also has the world’s largest population of herbivorous ungulates. By examining the modern predator/prey dynamics of the Serengeti, we hope to gain insight into the same relationships in the analogous Jurassic Morrison Formation. Guild structures for both the Morrison and Serengeti faunas were differentiated based on body masses. Average body masses of Serengeti fauna were easily obtained from the literature. Body mass estimates for the Morrison Formation fossil material were calculated from femur and humerus circumferences, and estimated circumference measurements constructed from a linear model. Species were then partitioned into weight classes and various biodiversity metrics, including species evenness, richness, and rank abundance, were calculated. Overall, each ecosystem exhibits the highest concentration of total biomass in one of its two megaherbivore weight classes - the Serengeti has the most biomass in the LGHB (100-1000 kg) weight category, and the Morrison has the most biomass in the MH1A (> 18000 kg) weight category. These weight categories both represent 91% of their total ecosystem biomass. Quantitatively comparing the Morrison and Serengeti ecosystem population counts by using the Kolmogorov-Smirnov test has shown they do not have a statistically significant difference between their diversities.