EXPLOITATION OF CRETACEOUS CRUSTACEANS: COPROLITIC EVIDENCE FOR OMNIVOROUS FEEDING BEHAVIOR IN LARGE, HERBIVOROUS DINOSAURS
At least eleven of thirteen examined coprolite deposits contain calcareous, shell-like fragments up to 2 x 3 cm in area and ~0.5 to 0.9 mm thick. Much of this material is diagenetically altered, but well-preserved fragments display nodes, pores, and internal laminae. The thickness, microstructure, and chemical composition of these fragments are all consistent with crustacean cuticle, though there is insufficient morphology to identify the type of crustacean in the coprolites. Nevertheless, the robust cuticle thickness and large fragments suggest that these invertebrates were sizeable and were intentionally consumed. Ingestion of crustaceans would have provided a nutritional windfall in terms of both protein and calcium. Such resources would have been particularly beneficial during the breeding season when extra calcium was needed for eggshell production and higher protein levels were required to provision eggs. It is notable that many extant avian dinosaurs alter their dietary habits during breeding to accommodate elevated requirements for protein and calcium. Although it might have been challenging for megaherbivorous dinosaurs to capture small, isolated arthropods, aggregations of invertebrates are common in rotting logs. This new evidence for omnivorous feeding behavior compels us to reevaluate presumptions that large herbivorous dinosaurs fed exclusively on vegetation.