Scratches on dinosaur teeth could reveal what they really ate
For the first time, dental microwear texture analysis (DMTA) has been used to infer the feeding habits of large theropods, including Allosaurus and T. rex.
By taking 3D images of individual teeth and analysing the pattern of marks scratched into them, researchers could reason which dinosaurs may have frequently crunched on hard bone and which may have regularly eaten softer foods and prey. This technique opens up a new avenue of research for palaeontology, helping us to better understand not only dinosaurs themselves, but also the environment and communities in which they lived.
From Fantasia to Jurassic Park, the T. rex is seen as a terrifying apex predator that would chase down its prey and crunch on it whole. But how much did this iconic dinosaur actually chow down on bones? And what about other predatory dinosaurs that existed long before it?
Researchers from the University of Tokyo, in collaboration with teams from the University of Mainz and the University of Hamburg in Germany, have used dental microwear texture analysis (DMTA), a scanning technique to examine topographical dental wear and tear in microscopic detail, on individual dinosaur teeth from more than 100 million years ago, to better understand what they may have eaten.
Postdoctoral fellow Daniela Winkler from the Graduate School of Frontier Sciences at the University of Tokyo, said: “We wanted to test if we could use DMTA to find evidence of different feeding behaviours in tyrannosaurids (from the Cretaceous period, 145 million to 66 million years ago) compared to the older Allosaurus (from the Jurassic period, 201 million to 145 million years ago), which are both types of theropods.
“From other research, we already knew that tyrannosaurids can crack and feed on bones (from studies of their faeces and bite marks on bone). But allosaurs are much older and there is not so much information about them.”
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DMTA has mainly been used to study mammal teeth, so this is the first time it was used to study theropods. The same research team from the University of Tokyo also recently pioneered a study on DMTA in Japanese sauropod dinosaurs, famous for their long necks and tails.
A high-resolution 3D image was taken of the tooth surface at a very small scale of 100 micrometres (one-tenth of a millimetre) by 100 micrometres in size. Up to 50 sets of surface texture parameters were then used to analyse the image, for example, the roughness, depth and complexity of wear marks.
If the complexity was high, i.e., there were different-sized marks which overlaid each other, this was associated with hard object feeding, such as on bone. However, if the complexity was low, i.e., the marks were more arranged, of a similar size and not overlapping, this was associated with soft object feeding, like meat.
In total, the team studied 48 teeth, 34 from theropod dinosaurs and 14 from crocodilians (modern crocodiles and alligators), which were used as a comparison. The team was able to study original fossilised teeth and take high-resolution silicon moulds, thanks to loans provided by natural history museums in Canada, the US, Argentina and Europe.
Winkler added: “It was especially challenging to carry out this research during the pandemic, as we rely on being able to gather samples from international institutions. The sample size might not be so large this time, but it is a starting point.”
Winkler says what they found surprising was that they didn’t find evidence of much bone crushing behaviour in either Allosaurus or tyrannosaurids, even though they know that tyrannosaurids ate bone.
There may be several reasons for this unexpected outcome. It could be that although Tyrannosaurus was able to eat bone, it was less commonly done than previously thought. Also, the team had to use well-preserved teeth, so it might be that extremely damaged teeth that were excluded from this study were in such a condition because those animals fed more on bone.
Something the team did find with both the dinosaurs and crocodilians was a noticeable difference between juveniles and adults.
Winkler said: “We studied two juvenile dinosaur specimens (one Allosaurus and one tyrannosaurid) and what we found was a very different feeding niche and behaviour for both compared to the adults.
“We found that there was more wear to juvenile teeth, which might mean that they had to more frequently feed on carcasses because they were eating leftovers.
“We were also able to detect different feeding behaviour in juvenile crocodilians; however, this time it was the opposite. Juvenile crocodilians had less wear on their teeth from eating softer foods, perhaps like insects, while adults had more dental wear from eating harder foods, like larger vertebrates.”
Image: Blue silicon was carefully excreted from a tube onto the teeth and left to dry for a few minutes to create near-perfect replicas, which were removed and taken from the museum in the US city of Salt Lake City, Utah, to Japan for further study. © 2022 DE Winkler.