Numerous Tyrannosaurus Rex skulls bear scars that indicate these predatory apes bit each other once they reached reproductive age.
Paleontologists found evidence of tooth marks within 60 percent of the adult specimens from 202 T. Rex fossils.
T. rex was the largest predator in North America during Late Cretaceous approximately 66 million years back. What on Earth could have made them so large to scrape their massive faces?
Scientists believe that the bites were caused by the same species' powerful jaws because of the height and spacing of the marks. The impression was impossible to make for any other carnivores in the continent at the time.
It was even more striking that the bite marks on T. rex skulls were consistent from one specimen to the next, which suggests a common behavior.
The majority of ancient lesions that were identified had been extensively healed, suggesting that the bites weren't fatal and could have occurred repeatedly throughout a person's lifetime once they reached sexual maturity.
These lesions were more common in males, but there were also bite marks found in some females. The biting behavior could have been a form of territorial telling off, to protect resources, or to fight against sexual competitors. It also may have been a part of T. Rex courtship.
The authors speculate that the reason behind the face-biting could have been related to territorial disputes, resource or mate contests, establishing dominance hierarchy, or courtship rituals.
Other research supports the idea. T. rex skulls were found with teeth from their own species in the past. This suggests that the species may have fought.
While some descendants still display similar behaviors, birds aren't nearly as bloodthirsty today as their dino ancestors. Instead, avians rely on song and dancing to display their vocal and feathers to potential mates or aggressors.
Perhaps that is a luxury that evolves with plumage. According to the authors, dinosaurs used their natural advantage of having sharp jaws and reptilian skin to their advantage.
According to the study, the orientation and location of the bite patterns found in the study suggests that one T. Rex would often stand next to another T. rex when it was ready for battle. They would then swing their heads from side to side and attempt to grab the skull or lower jaw of their victim using their teeth.
A successful bite could puncture the skin, leaving a circular lesion around the jawbone. However, a quick blow will leave only a small scratch.
The behavior of crocodiles is very similar to that of salamanders or some alligators. These living animals may also be able to preempt the attack by displaying aggressive behavior or making visual threats. This could indicate that the T. Rex might have done something similar prior to getting in for a bite.
That's conjecture at the moment. However, Paul Barrett, a paleontologist who wasn't involved in the study, told The Natural History Museum that the analysis of T.rex bite marks was a wonderful new insight.
He says, "The team convincingly shows that even though earlier-evolving meat-eating dinosaurs had croc-like behavior in fighting with each other, this disappears as feathers evolve, and allows display to take over from eating."
"It's incredible that we can get these direct insight into fossilized behavior, which have been frozen time-wise as marks on their bone."
The study was published by Paleobiology.