Thread by @BradtheCurator

Attacks or accidents? A thread for #FossilFriday!
Several hadrosaurs have been found with serious, oval shaped injuries to the tall spines along the tops of their tail. Some paleontologists have suggested that these are from unsuccessful attacks by tyrannosaurs. But are they?1/11

The two best specimens are a Brachylophosaurus (JRF1002) and an Edmontosaurus (DMNH1493) with strikingly similar injuries. In both cases the bones had begun healing after the injury occurred, so while these may have contributed to the animals deaths they likely weren't the cause.

Both genera were predated on by large tyrannosaurs, so it's possible that these were bite marks from attacks that ended with the hadrosaur managing to escape. Indeed, the shape and size would be roughly congruent with a bite mark from the local tyrannosaur genera.

What else could it have been? Another hadrosaur! While the injuries can be said to resemble tyrannosaur bites, they also nicely line up with the feet of other hadrosaurs, and the misplaced step of an adult hadrosaur would have been more than enough to do the damage seen here.

In fact, the way in which the bones were healing seems to more closely resemble an accident like this than the bite of a hungry tyrannosaur. Tyrannosaur bites tend to leave specific grooves and heal with an almost blister-like pattern, which is not the case in either specimen.

On top of that, hadrosaurs were hurting their tails on a somewhat regular basis- its the most common place to find injuries on them, particularly fractures. Given that these were massive, multi-ton #dinosaurs that were likely moving in dense herds, accidents were bound to happen.

In fact, one paper encouraged paleoartists "who render hadrosaur reconstructions to
include some with caudal injuries. This would include animals with distal ends of tails missing, swollen, or with the tail tip deflected dorsally or laterally at angles of about 10-25°."

The injuries might not have always been that accidental, either, as sexually mature hadrosaurs competing for mates and resources could easily have caused these sorts of injuries to one another. Even the act of mating itself might have caused such injuries, especially to tails.

As is often the case in #paleontology, without a "smoking gun" specimen of some sort we can't know for certain one way or the other- all we can do is look at the evidence left to us and use our best judgement and the scientific method to outline the most likely conclusions.

Works cited:
"Paleopathology in Late Cretaceous Hadrosauridae from Alberta,
Canada: with comments on a putative Tyrannosaurus bite injury
on an Edmontosaurus tail ," by Darren H. Tanke and Bruce M. Rothschild.

A big thanks to @df9465 and @DavidEvans_ROM for mentioning these ideas and sending me down this awesome paleopathology rabbit hole.

Works cited:
"Paleopathology in Late Cretaceous Hadrosauridae from Alberta,
Canada: with comments on a putative Tyrannosaurus bite injury
on an Edmontosaurus tail ," by Darren H. Tanke and Bruce M. Rothschild.

"New Evidence for Predation by a Large Tyrannosaurid," by Nate L. Murphy, Kenneth Carpenter, and David Trexler
"Evidence of Predatory Behavior by Carnivorous Dinosaurs,"
by Kenneth Carpenter.

Artwork by:
Tracy Ford
Atrox1 on DeviantArt