Competition structured a Late Cretaceous megaherbivorous dinosaur assemblage

Jordan C Mallon

doi:10.1038/s41598-019-51709-5

Abstract

Modern megaherbivore community richness is limited by bottom-up controls, such as resource limitation and resultant dietary competition. However, the extent to which these same controls impacted the richness of fossil megaherbivore communities is poorly understood. The present study investigates the matter with reference to the megaherbivorous dinosaur assemblage from the middle to upper Campanian Dinosaur Park Formation of Alberta, Canada. Using a meta-analysis of 21 ecomorphological variables measured across 14 genera, contemporaneous taxa are demonstrably well-separated in ecomorphospace at the family/subfamily level. Moreover, this pattern is persistent through the approximately 1.5 Myr timespan of the formation, despite continual species turnover, indicative of underlying structural principles imposed by long-term ecological competition. After considering the implications of ecomorphology for megaherbivorous dinosaur diet, it is concluded that competition structured comparable megaherbivorous dinosaur communities throughout the Late Cretaceous of western North America.

Highlights

The question of which mechanisms regulate species coexistence is fundamental to understanding the evolution of biodiversity[1]
The community ecology, and the coexistence of its constituent species, has proved especially perplexing as it relates to the megaherbivorous dinosaur assemblage of the Late Cretaceous island continent of Laramidia
If dietary resources on Laramidia were limiting to megaherbivores, species overlap in ecomorphospace should have been minimized, which would have reduced resource competition and facilitated dietary niche partitioning among sympatric species

Summary

Introduction

The question of which mechanisms regulate species coexistence is fundamental to understanding the evolution of biodiversity[1]. Of particular note is the fact that dinosaurian predators were much larger than those of today[6] (Fig. 1), and likely would have posed a significant threat to even the largest herbivores of their time (with the possible exception of the biggest sauropods) This is especially true if large theropods were capable of cooperative hunting, a hypothesis that has garnered some support from both bonebed and trackway evidence[7,8,9]. The community ecology, and the coexistence of its constituent species, has proved especially perplexing as it relates to the megaherbivorous dinosaur assemblage of the Late Cretaceous island continent of Laramidia. The remainder of this paper will focus on demonstrating P3 and P4, which are the manifestations of P1 and P2, respectively

Methods

Results

Discussion

Conclusion