Jurassic dinosaurs had specialized diets to coexist peacefully

What dinosaurs ate has long fascinated scientists. Now, fossilized teeth tell the story in surprising detail. By analyzing chemical traces in tooth enamel, researchers have uncovered distinct diets among Late Jurassic dinosaurs.

A study from The University of Texas at Austin shows that different species did not just live side by side. They also had unique food preferences. These eating habits helped them thrive together without competing for the same plants.

Calcium isotopes in enamel carry chemical fingerprints from ancient meals. Different plants, and even plant parts like bark or buds, leave different traces. This evidence reveals which dinosaurs ate what and how their diets shaped their ecosystem.

“The idea is that they were all eating different things, and now we have found proof of that,” said study lead author Liam Norris, a recent doctoral graduate from UT’s Jackson School of Geosciences.

How dinosaurs lived together

Norris studied fossils from a single deposit at Carnegie Quarry in northeast Utah. This site, rich with bones from herbivorous and carnivorous species, likely formed during an intense drought. Its rapid fossil preservation made it ideal for comparing diets across species living at the same time and place.

The herbivores in the study included Camarasaurus, Camptosaurus, and Diplodocus. Carnivores included the Allosaurus and the croc-like Eutretauranosuchus.

Norris collected enamel samples from 17 individual animals, either accessed in the field or loaned by local museums. At the Jackson School, he conducted isotope analysis with support from co-authors John Lassiter and Aaron Satkoski.

Professor Rowan Martindale called the site “a unique paleontological gem.” The research deepens our understanding of ancient ecosystems and dietary preferences.

Plant-eating dinosaurs had different diets

Earlier theories assumed large herbivores ate from different vertical zones of the forest canopy. But Norris found that diet separation was more nuanced. For example, Camptosaurus favored soft, nutritious plant parts like leaves and buds.

Camarasaurus preferred conifers and tougher, woody plant tissues. Diplodocus had a more varied menu of low-lying ferns, horsetails, and coarse materials.

“This differentiation in diet makes sense with what we see from the morphology of these animals: the different height, the different snout shape. Then, we bring in this geochemical data, which is a very concrete piece of evidence to add to that pot,” said Norris.

These findings support the idea that long-necked dinosaurs had flexible necks allowing them to reach different plant levels. Instead of competing, they targeted specific vegetation patches suited to their anatomy and energy needs.

Diet choices of carnivore dinosaurs

The two carnivores in the study, Allosaurus and Eutretauranosuchus, showed overlapping isotope values, suggesting some dietary similarities. But subtle differences hinted at distinct prey choices and ecological roles.

Allosaurus, a large bipedal predator, likely hunted herbivorous dinosaurs, including Camptosaurus and other smaller or juvenile plant-eaters within the same region. Its size, jaw structure, and teeth suggest active predation or scavenging of large-bodied prey.

Eutretauranosuchus, in contrast, was smaller and more crocodile-like. Its isotope signature indicates it may have consumed fish or small terrestrial vertebrates, likely along rivers or shallow wetlands.

The hunting strategy and habitat of Eutretauranosuchus likely differed greatly from the Allosaurus, reducing competition between the two carnivores despite their coexistence.

These dietary contrasts reflect ecological separation shaped by behavior, anatomy, and environment. Such distinctions help reconstruct predator-prey dynamics within this Jurassic ecosystem.

The overlapping yet diversified food chain reveals how balance existed even during environmental stress, such as the severe drought that led to the rapid fossil preservation at Carnegie Quarry.

Many dinosaurs shared one ecosystem

The fact that so many massive animals thrived together points to a lush, productive ecosystem teeming with plant life. Their dietary specialization hints at a world where resource use was efficient and competition was minimal.

“It’s really just more proof that this ecosystem was as spectacular as we thought it was,” Norris said.

The study offers not just a clearer view of dinosaur life and diet but also a method for understanding other prehistoric ecosystems through geochemistry.

The study is published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.

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