Evrim Yazgin
Cosmos science journalist
Palaeontologists in Australia have uncovered the first stomach contents of a sauropod giving insights into the diets of the largest land animals of all time.
Diamantinasaurus matildae is a sauropod which has been found in the sheep-grazing country around Winton in the Australian state Queensland. Several Diamantinasaurus specimens have been found over recent years dating to the middle of the Cretaceous period which lasted 145 to 66 million years ago (mya).
Like most sauropods, Diamantinasaurus was massive with adults measuring about 20 tonnes and 16m in length.
One Diamantinasaurus fossil of a 12m-long subadult, affectionately called “Judy”, which lived 101–94 mya is special because it preserves the fossilised gut contents – also known as a cololite – of the animal. It is described in a paper published in the journal Current Biology.
“No genuine sauropod gut contents had ever been found anywhere before, despite sauropods being known from fossils found on every continent and despite the group being known to span at least 130 million years of time,” says lead author Stephen Poropat of Western Australia’s Curtin University.
“This finding confirms several hypotheses about the sauropod diet that had been made based on studies of their anatomy and comparisons with modern-day animals.”
Dinosaur diet helps paint a picture of how these remarkable animals lived millions of years ago.
Without direct gut contents, palaeontologists have to rely on indirect evidence such as the shape of ancient animals’ teeth, skulls and necks to determine what they ate.
Analysis of the plants in the Diamantinasaurus cololite not only showed which kinds of vegetation the sauropod fed on, but that the giant did no chewing.
“The plants within show evidence of having been severed, possibly bitten, but have not been chewed, supporting the hypothesis of bulk feeding in sauropods,” says Poropat. The giant creatures would instead have relied on fermentation in their gut for digestion.
Among the plant matter was includes foliage from conifers (cone-bearing seed plants), seed-fern fruiting bodies (plant structures that hold seeds), and leaves from angiosperms (flowering plants), indicating that Diamantinasaurus was an indiscriminate feeder. They preferred new growth sections of the plants which are easier to digest.
“By using advanced organic geochemical techniques, we were able to confirm the presence of both angiosperms (flowering plants) and gymnosperms (non-flowering, woody plants including conifers) in the diet of this sauropod,” says Kliti Grice, also from Curtin. “This unique approach was what provided molecular evidence of the plants that sauropods consumed.”
Flowering plants had evolved only about 40 million years before Diamantinasaurus roamed, meaning these sauropods adapted to eat these new plants relatively quickly.
“This implies that at least some sauropods were not selective feeders, instead eating whatever plants they could reach and safely process,” Poropat says. “These findings largely corroborate past ideas regarding the enormous influence that sauropods must have had on ecosystems worldwide.”
The findings suggest that Diamantinasaurus likely fed on both low- and high-growing plants, at least before adulthood.
But, Poropat stresses that more sauropod cololites would help build a better picture of the dinosaur group’s diets.
“These gut contents only tell us about the last meal or several meals of a single subadult sauropod individual,” Poropat says. “We don’t know if the plants preserved in our sauropod represent its typical diet or the diet of a stressed animal. We also don’t know how indicative the plants in the gut contents are of juvenile or adult sauropods, since ours is a subadult, and we don’t know how seasonality might have affected this sauropod’s diet.”
