Differences in diet among multiple species of sauropods - largest animals to have ever roamed the Earth - allowed them to coexist in prehistoric ecosystems, scientists have found.
The sauropods - large, long-necked plant-eating dinosaurs such as Diplodocus and Brachiosaurus - dominated the land between 210 and 65 million years ago.
They were the largest land animals of all time, with the biggest weighing 80 tonnes (more than 11 elephants) and would have needed vast amounts of food.
Despite this, multiple sauropod species often lived alongside each other. The most notable example is the community of the Late Jurassic Morrison Formation, a distinctive sequence of sedimentary rock in the western US from which over 10 species of sauropod are known.
How so many giant herbivores could have coexisted has long been a mystery: even the highly diverse faunas seen in modern Africa only support one truly gigantic species, the elephant, researchers said.
This is made even more puzzling by the harsh, semi-arid environment of the Morrison Formation during the Jurassic, which would have limited plant growth, researchers added.
The study conducted by David Button, a PhD student in University of Bristol's School of Earth Sciences and the Natural History Museum, London focused on the skull and jaws of sauropods, using a variety of biomechanical techniques to investigate how they functioned and what this would mean for sauropod ecology.
Using CT scans, the researchers digitally reconstructed the skulls of Camarasaurus and Diplodocus, along with the jaw and neck muscles of both species from the traces left on the bones where these muscles were attached in life.
These two species are very common in the Morrison Formation, and are known to have widely co-existed.
From this data, a biomechanical computer model of the skull of Camarasaurus was built.
This model was then compared to a pre-existing model of Diplodocus in order to investigate how the dinosaurs fed.
"Our results show that although neither could chew, the skulls of both dinosaurs were sophisticated cropping tools. Camarasaurus had a robust skull and strong bite, which would have allowed it to feed on tough leaves and branches," Button said.
"Meanwhile, the weaker bite and more delicate skull of Diplodocus would have restricted it to softer foods like ferns.
"However, Diplodocus could also have used its strong neck muscles to help it detach plant material through movements of the head. This indicates differences in diet between the two dinosaurs, which would have allowed them to coexist," he said.
The researchers also used a series of biomechanical measurements from other sauropod species to calculate the functional disparity in their skulls and jaws and found that other Morrison Formation sauropods were also highly varied in feeding adaptations, suggesting different diets.
The research is published in Proceedings of the Royal Society B.
