Experts Reveal Dinosaur Predator-Prey Dynamics from Bite Marks

WASHINGTON – In the treacherous Jurassic Period landscape of western North America, being big was a good thing. Your life may depend on it.

Paleontologists conducted research by examining bite marks left by meat-eating dinosaurs on the bones of sauropods – plant-eating dinosaurs with long necks, long tails and four pillar-like legs that were the largest land animals that ever existed – about 150 million years old. ago. The examination provides insight into predator-prey dynamics during the age of the dinosaurs.

Of the approximately 600 bones examined, bite marks – often deep indentations left in sturdy bones – were detected on 68 bones, covering 40 individual sauropods and representing at least nine species.

The nature of the bite led researchers to an interesting conclusion. These markings appear to have been made not by predators hunting and killing adult sauropods, but rather through scavenging by meat eaters who discovered the bodies of sauropods that had died from causes such as old age or weakness.

It might have been too risky, they said, for a predator – even one that weighed several tons – to try to kill an adult sauropod that might have been five to 10 times as large as Brachiosaurus.

“While this happens occasionally, we couldn’t find any injuries that might have been caused by predation attempts,” said paleontologist David Hone of Queen Mary University of London, who helped lead the research published this week in the journal PeerJ Life. & Environment.

“The fact that we do not see healed bite marks from predation attempts on adult sauropods is consistent with the idea that they were not normally targeted by predators. This can happen to old, sick, injured or other vulnerable animals. But in general, predators probably avoid them,” Hone added.

Sauropods, the largest land animals in Earth’s history, first appeared about 200 million years ago and lived until the end of the dinosaur era 66 million years ago.

Meat-eating dinosaurs were all members of a group called theropods. And there were large species roaming around during this study, including Allosaurus, Torvosaurus, Ceratosaurus, and Saurophaganax. However, they were inferior to adult sauropods, which may have weighed up to 50 tons.

“At that point, the prey has more options to harm the predator than vice versa. A single kick or blow of the tail from a large sauropod could potentially be fatal. “Often, there were more young sauropods around, so a theropod would have been suicidally determined to attack an adult,” said study co-author Mathew Wedel, an anatomist and paleontologist at Western University of Health Sciences in California.

The fossils in this study come from rocks called the Morrison Formation which are spread across 13 states in the western United States. Bites were detected on sauropod bones belonging to Camarasaurus, Galeamopus and Suuwassea as well as bones possibly but not definitely belonging to Diplodocus, Apatosaurus and Brachiosaurus.

The fact that theropods apparently avoided hunting adult sauropods doesn’t mean sauropods weren’t on the menu. The researchers noticed a high degree of wear on fossil theropod teeth that was disproportionate to the rareness of bites on adult sauropod bones.

“Dinosaurs all laid eggs, and the largest sauropods probably laid hundreds of eggs each year. So the number of babies, juveniles, and sub-adults always outnumbers the adults. We suspect that large theropods had already begun to lose the teeth to attack, kill and destroy entire eggs. ate young sauropods, which would not have left bitten bones to fossilize,” Wedel said.

“If you’re an Allosaurus, most of the sauropods you’ll ever encounter are young sauropods, and for the first few years of their life, they’re almost helpless,” Wedel added. “So it is perhaps not surprising that we find such a large diversity of predators in the Morrison Formation. Sauropods basically provided them with endless food.”