Dinosaur teeth have been studied many times already. Scratches and pits on the surface of herbivore teeth provide clues to how they fed, and what types of plants they fed on. But many of these studies look at only a few teeth, or only a few specimens. Not so with this study.
In a great new paper in PLOS ONE, researchers from the University of Calgary examined teeth from 76 individual dinosaurs across 16 different Alberta dinosaur species. This was many hundreds of individual teeth, representing a huge swath of multiple dinosaur ecosystems in what is now Alberta's Dinosaur Park Formation.
The DPF was, in the late Cretaceous, a crowded place for plant-eating dinosaurs, with around six separate megaherbivore (1000kg+) species browsing the same territory at any given time. (For comparison's sake, today's Serengeti is home to only four megaherbivores.)
And this is where the headline comes in: despite having so many different massive plant eaters at once (two different ankylosaurs, two different ceratopsians, and two different hadrosaurs), the megaherbivores of ancient Alberta were able to share their habitats with each other by eating different types of plants, and feeding at different heights. Everyone got along and it was basically The Land Before Time up there.
Among the interesting findings:
- Ankylosaurs ate fruit! Their teeth have all the characteristic pitting of something that bit into a lot of tiny hard seeds. For some reason I had always filed away fruit as a post-dinosaur thing, but although grass didn't appear until just before they died out, fruit and dinosaurs seem to have co-existed for at least 64 million years. Ankylosaurs may have had a more seasonally-varied diet than their contemporaries, and could apparently handle tougher leaves than conventionally believed, but soft plants and fruit were certainly a part of their diet.
- Ceratopsians ate only the tough stuff. Woody browse, including lots of thick leaves and twigs, probably made up the bulk of the ceratopsian diet. They also stayed low, sticking to what grew lower than a meter off the ground. This was already the prevailing view among ceratopsian researchers, but this study looked at it from angles that hadn't been considered before, providing further validation.
- Hadrosaurs (duckbills) ate basically everything. There has been some dispute about hadrosaur feeding in the literature recently, with some authors using tooth wear to assert that hadrosaurs were restricted to low-growing soft plants (which would put them directly in competition with ankylosaurs). This new (and much broader) tooth study agrees with the earlier view (supported by coprolites and gut contents as well) that hadrosaurs were equal opportunity browsers, browsing on sprout, leaf, fruit, twig, needle, and rotting wood alike. The hadrosaurs' size and posture also allowed them to browse much higher than ankylosaurs and ceratopsians, allowing each its own niche.
So there it is. Ankylosaurs ate low-growing soft plants, ceratopsians ate low-growing tough plants, and hadrosaurs ate everything too high for ankylosaurs and ceratopsians to reach, up to about 5m. Nothing too revolutionary, but fun to read about regardless.
Mallon, Jordan and Anderson, Jason. The Functional and Palaeoecological Implications of Tooth Morphology and Wear for the Megaherbivorous Dinosaurs from the Dinosaur Park Formation (Upper Campanian) of Alberta, Canada. June 11, 2014. DOI: 10.1371/journal.pone.0098605
Figure at top is taken from the paper.