Washington: A new study helps answer a long-standing question in palaeontology, as to how numerous species of large, plant-eating dinosaurs could co-exist successfully over geological time.
Dr. Jordan Mallon, a post-doctoral fellow at the Canadian Museum of Nature, tackled the question by measuring and analyzing characteristics of nearly 100 dinosaur skulls recovered from the Dinosaur Park Formation in Alberta, Canada.
The specimens now reside in major fossil collections across the world, including that of the Canadian Museum of Nature.
The work was undertaken as part of his doctoral thesis at the University of Calgary under the supervision of Dr. Jason Anderson.
Mallon`s results indicate that these mega herbivores (all weighing greater than 1,000 kg) had differing skull characteristics that would have allowed them to specialize in eating different types of vegetation.
The results support a concept known as niche partitioning, which dates to the 19th-century studies of Charles Darwin and came into its own in the 1950s with the development of the science of ecology.
The Dinosaur Park Formation is between 76.5 and 75 million years old and is known for its rich concentration of dinosaur remains.
The rock unit has yielded nearly 20 species of mega herbivores from the Late Cretaceous period.
Of these, six species would have coexisted at any one time, including two types of ankylosaurs (tank-like armoured dinosaurs), two types of hadrosaurs (duck-billed dinosaurs), and two types of ceratopsids (horn-faced dinosaurs).
Modern mega herbivores include elephants, giraffes, hippos and rhinos.
"Today`s mega herbivore communities are not nearly as diverse as those from the Late Cretaceous of Alberta, and most other fossil communities also pale by comparison. So the question is: how does an environment support so many of these large herbivores at once?" Mallon said.
Mallon tested two competing hypotheses. The first is that availability of food was not a limiting factor in species survival. Plants may have been either super-abundant, so the mega herbivores did not have to compete for food, or the dinosaurs` metabolisms were relatively low, so the environment could support more species relative to a fauna comprised entirely of high-metabolic animals.
The second hypothesis is that the available food resources were limiting and that niche partitioning came into play; in other words, there weren`t that many plants to go around so that the species had to share available food sources by specializing on different types of vegetation.
The study is published in the open-access journal PLOS ONE.