Browsing by Author "Mallon, Jordan"

Now showing 1 - 1 of 1
  • Thumbnail Image
    ItemOpen Access
    Evolutionary palaeoecology of the megaherbivorous dinosaurs from the Dinosaur Park Formation (upper Campanian) of Alberta, Canada
    (2012-07-30) Mallon, Jordan; Anderson, Jason
    During the Late Cretaceous, megaherbivorous dinosaurs flourished in the Western Interior of North America (Laramidia). At any one time, there were typically two ankylosaurs (one ankylosaurid plus one nodosaurid), two ceratopsids (one centrosaurine plus one chasmosaurine), and two hadrosaurids (one hadrosaurine plus one lambeosaurine) living in sympatry. This diversity exceeds that of living megaherbivorous mammal communities, and is only rarely observed in the mammalian fossil record. Opinions differ about how this diversity was achieved. Some have argued that megaherbivorous dinosaurs thrived because of their low metabolic rates, or because of high primary productivity during the Late Cretaceous, implying that food resources were not limiting. A similar outcome might have been achieved if predation pressure from theropods was sufficiently high to depress megaherbivore population densities, leading to reduced demand on plant resources. Others have argued that dietary niche partitioning played an important role in the coexistence of these animals, with each species consuming a different plant resource than the next, thereby minimizing interspecific competition. This dissertation uses the megaherbivorous dinosaur assemblage from the upper Campanian Dinosaur Park Formation (DPF) of Alberta, Canada, as a model to test the dietary niche partitioning hypothesis by examining several aspects of ecomorphology known to relate to the procurement and mastication of food. These include feeding height, skull and beak morphology, jaw mechanics, and tooth morphology and wear. Evidence is sought for taxonomic separation in ecomorphospace, particularly between coexisting species, which is known to reflect niche relationships with some fidelity. Although sympatric taxa are better discriminated by some features than others, consideration of the total evidence supports the dietary niche partitioning hypothesis, as even the most closely related, sympatric taxa can be statistically distinguished according to their ecomorphology. Whether these dietary niche relationships arose as a result of long-term competition, or whether they evolved allopatrically is not clear. However, the fact that consubfamilial species coexistence was uncommon—and when it did occur, was either short-lived or involved only rare species—implies that the structure of the megaherbivorous dinosaur assemblage from the DPF was at least partly influenced by competitive interactions.