Bone bite marks reveal dinosaur predator-prey dynamics. It was good to be huge on the treacherous western North American landscape of the Jurassic Period. It might have affected your life.
Examining the bite marks that carnivorous dinosaurs left on the bones of sauropods—the well-known plant-eating dinosaurs with long necks, long tails, and four pillar-like legs that were the largest land animals in existence 150 million years ago—paleontologists have done research. The analysis shed light on the dynamics of predator-prey in the dinosaur era.
Of the almost 600 bones examined, 68 had bite marks—deep grooves left in sturdy bone—corresponding to 40 different sauropods and at least nine species.
Based on the characteristics of the bites, the researchers came to a fascinating conclusion. Instead of predators who had hunted and killed the adult animals, scavengers who came across the carcasses of adult sauropods already dead from illnesses or old age appear to have made these marks.
They claimed it might have been too dangerous for a predator, even one weighing several tons, to attempt to take down an adult sauropod that was possibly five to ten times more enormous than Brachiosaurus.
This week, the journal PeerJ Life & Environment published the study, which paleontologist David Hone of Queen Mary University of London co-led. “While it must have happened occasionally, we can’t find any wounds that would likely be the result of predation attempts,” Hone said.
The lack of features like healed bite marks from attempts at predation supports the idea that these adult sauropods were not typically the target of predators. The elderly, ill, wounded, or other defenseless animals would have suffered the same fate. However, predators most likely avoided them altogether in general, Hone continued.
With their emergence approximately 200 million years ago, sauropods were the largest terrestrial animals in Earth’s history. They continued to exist until the end of the dinosaur era, 66 million years ago.
Dinosaurs that consumed meat belonged to a group known as theropods. And throughout the research period, several massive ones were out and about, including Allosaurus, Ceratosaurus, Torvosaurus, and Saurophaganax. However, adult sauropods weighing up to fifty tons overshadowed them.
“At that time, the prey has many more ways than the predator to harm it. A giant sauropod’s tail swipe or kick might be lethal in one instance. A theropod would have needed to be suicidally motivated to attack an adult since, most of the time, there would have been a lot more young sauropods nearby, according to research co-author Mathew Wedel, a paleontologist and anatomist at Western University of Health Sciences in California.
The study’s fossils originated from rocks in 13 western states that are part of the Morrison Formation. Bones from Camarasaurus, Galeamopus, and Suuwassea, and bones that are most likely, but not definitely, from Diplodocus, Apatosaurus, and Brachiosaurus, were found to have bite marks.
Even though theropods don’t seem to have hunted adult sauropods, sauropods were still a possible food source. Researchers found that theropod tooth fossils had high degrees of wear that did not match the frequency of bites on adult sauropod bones.
“All dinosaurs laid eggs, and the most giant sauropods likely laid hundreds of eggs annually. Therefore, there were always more newborns, juveniles, and subadults than adults. We believe that the large theropods were wearing down their teeth while attacking, murdering, and devouring juvenile sauropods since they wouldn’t have left any bitten bones for fossilization, according to Wedel.
“If you’re an Allosaurus, the vast majority of the sauropods you ever encounter will be young ones, and for the first few years of their lives, they will be almost defenseless,” Wedel said. Therefore, it should come as no surprise that the Morrison Formation contains many large carnivores. In a sense, the sauropods were providing them with an endless feast.”