Dinosaur dentures: as rare as sauropod teeth

Extremely rare sauropod dinosaur teeth found in Queensland have enabled researchers “to put the smile back on the sauropod”, says palaeontologist Dr Stephen Poropat.

Poropat is the lead author of a paper published in the Royal Society Open Science this week, and a researcher at the Australian Age of Dinosaurs Museum in Winton, Queensland.

Sauropods were long-necked dinosaurs, the largest Australian land animals of all time. The fossilised sauropod teeth were found in the Winton Formation in western Queensland. 

And while such teeth are commonly found in fossil deposits elsewhere in the world, in Australia, sauropod teeth are as rare as … well, sauropod teeth. 

Poropat told Cosmos this might be because there aren’t many rocks of Jurassic or Cretaceous age exposed at the surface in Australia, and those that are haven’t been extensively explored. Even the Winton Formation, which has produced several sauropod skeletons including baby Sauropod “Ollie”, examples of teeth and head fragments have been extremely rare. 

That changed in 2019 and 2021 when palaeontologists excavated 17 sauropod teeth at the “Mitchell” site on a sheep station located 60 kilometres west-northwest of Winton. These were analysed together with a dental fragment and tooth from the nearby “Matilda” site, and a single tooth from the “Alex” site, 60km northeast of Winton.

Poropat says that while people might expect a plant-eating animal to have molars for grinding, the sauropod teeth “couldn’t be further from that”.

“The simple fact is that sauropods didn’t chew their food.” 

The teeth from the Winton Formation were all very similar – sort of conical, then curved and pointed at the end; perfect for snipping plants. 

“Then they would use what was presumably a pretty long and muscular tongue […] to then pull the food straight down the gullet,” says Poropat. “Essentially, once they had swallowed their food – basically no processing in the mouth at all, no chewing – they would pass it through to the rest of the digestive system. And it would basically act as giant fermenting vats.

“It’s been hypothesised that sauropods might have actually kept any given meal within their bodies for up to two weeks before excreting.”

Wear markings on five of the teeth allowed the researchers to infer that the dinosaur’s teeth would have been a bit offset. Scratches and pits on the teeth indicated that sauropods probably fed on plants from at least one metre above the ground, up to as much as 10m. That’s as high as a sauropod could reach if it reared on its hind legs, stretched out its neck and reached far up into the canopy.

Its lunch might have included conifers, gingkos and flowering plants given plant fossils found in the area. 

Poropat says horsetails, a plant which is extinct in Australia today but still exist in the northern hemisphere, would have made a “good, nutritious and easily accessible meal”. He thinks these would have been a favourite food for sauropods.

To analyse the wear patterns on the sauropod teeth, the paper’s second author Timothy Frauenfelder made casts of the teeth which were coated in a very thin layer of gold, enabling them to be scanned using an electron microscope.

The researchers have since found even more teeth at the Mitchell site, too late to be included in this paper, but likely to be the focus of further research.