The hapless dinosaur may have broken his wrist while sprinting. And with that, he suffered a difficult, but not insurmountable injury.

An international team of researchers writes this in the magazine Historical Biology† Their study deals with a bone that they found in a quarry near Blagoveshchensk, a city located in Russia’s far east. The bone belongs to Amurosaurus riabinini: A four-legged, herbivorous dinosaur that lived in the area some 68 million years ago.

Wrist

It soon became clear that it was on a young man’s wrist A. riabinini went. And that wrist had clearly been broken. According to researcher Filippo Bertozzo, the injury must have hindered the dinosaur considerably, but not in such a way that it immediately died. “Against all odds, the dinosaur appears to have survived the accident, as we see that the bone has already started to heal, suggesting that the animal did not die immediately. However, it seems likely that the injury caused the animal to limp on three legs and that must have affected its chances of escaping when predators showed up.”

Jump or run

An analysis of the broken bone also sheds light on how the dinosaur injured itself. For example, based on the type of fracture, the researchers think that the dinosaur broke its wrist while running or jumping. A collision with a predator is theoretically also a possibility, Bertozzo acknowledges, but is less likely. “The dinosaur walked on four legs, so it’s more likely that it defended itself by kicking with its hind legs or hitting with its tail. A kick from the front legs is not so plausible. In addition, we also did not find any teeth marks or traces of an infection that could have been caused by saliva from a predator on the bone. Therefore, the hypothesis that the animal broke its arm as it moved seems more plausible.”

And although the fracture must have been in the way of the dinosaur, it still managed to save itself for quite some time after the accident – while hopping. “We think that the amurosaurus lived for at least four to five months after the accident,” said Bertozzo. It’s unclear how the animal eventually died, but predators may have had a hand in it. “The broken wrist caused the animal to limp and possibly get hunted by predators. After all, we see today that predators such as lions often prey on the individuals in a herd that are either young, old or defective. Also an injured young adult amurosaurus would have been much easier prey for predators than a full-grown, healthy adult.”

Implications

It is quite common for researchers to come across broken dinosaur bones. Still, this latest discovery is very welcome and valuable, explains Bertozzo. The discovery provides a little more insight into how injured dinosaurs moved. And in the case of A. riabinini Thanks to this one bone, we can also get a better understanding of how the hadrosaurs – for what purpose? A. riabinini reckoned – moved in good health. “In the past, hadrosaurs have also been seen as bipedal animals that dragged their tails along the ground. Later they were set up as semi-four-legged with a high tail that carried them horizontally some distance from the ground. And today we still don’t quite know how they moved; did they continue to walk on four legs and how exactly did they run? The injury now suggests that the animal exacerbated its condition by placing its hands on the ground from time to time to delay its recovery, something that would be difficult to explain had the animal been truly bipedal.”

And finally, the research also provides a glimpse into the everyday life of these dinosaurs. “It reminds us that even the majestic dinosaurs could have accidents,” said study researcher Eileen Murphy. Bertozzo sees it the same way. “Illnesses and injuries give us a glimpse into the life of dinosaurs. They tell more about their lifestyle and behaviors that are otherwise difficult or even impossible to trace.” Think, for example, of injuries that dinosaurs suffered because they crossed swords with congeners or because a tyrannosaurus was after them. “It can also give us more insight into their metabolism and physiology; we can study how quickly their injuries healed or how long they managed to survive with their condition.”