Hadrosaur Tail Injuries

Researchers have long noted pathologies in the caudals of duckbilled dinosaurs. Some of these clearly resulted from predation. Inb 1988, Kenneth Carpenter described mangled neural spines in a DMNS Edmontosaurus. The damage across several spines, he wrote, "appears to delineate the mouth of a large predator," presumably the contemporary Tyrannosaurus.

More recently, paleontologists discovered a swollen hadrosaur caudal centrum. There is no doubt about the cause of the pathology. A tyrannosaur tooth is embedded in it.

Not all of the damage resulted from attempts at predation. The majority of mangled tails resulted from trampling, probably by others in a herd. Damage to female neural spines during mating is a possibility. It seems odd, though, that something as essential as procreation would be routinely injurious. Moreover, it is noteworthy that iguanodonts don't display the same caudal injuries as duckbills. That may be because iguanodonts, unlike hadrosaurs, probably stood and fought (with thumb spikes) instead of fled.

Even the trampled tails provide indirect evidence of predation. Under ordinary circumstances, when a hadrosaur herd was just resting or browsing, accidental stepping on a tail seems unlikely. Hadrosaurs had good vision. Even in crested taxa the view below them (as opposed to above or behind) was unobstructed. Herd members could easily see and avoid the tails of those lying on the ground--the only ones vulnerable to trampling as the stiffened tails were held off the ground when the animals got up. Occasionally, however, things got chaotic. When an approaching tyrannosaur was detected and a herd member sounded the alarm, a common result may have been a stampede. Throwing caution to the wind, many hadrosaurs could've run over the tails of others in a mad scramble to escape. Therefore, it's possible even damaged tails showing no evidence of toothmarks or teeth testify to the threats duckbills faced in their environments.

References

Carpenter, Kenneth 1988 Evidence of Predatory Behavior in Tyrannosaurus

Hadrosaurs Indiana University Press 2014

Tyrannosaur tooth embedded in hadrosaur centrum.