For a long time now a question that has teased palaeontologists is why the Triceratops had three horns, as well as the distinctive bony frill sticking out from the base of their skulls. Were they weapons for defence or attack? Or were they conspicuous adornments used to show off to other dinosaurs?
Now a team of researchers from the US and Canada think they have found the answer to this dinosaur Just-so story, with evidence that they used their elaborate head gear to do battle with other Triceratops.
The study was published in the journal Plos ONE this week and led by Andrew Farke, curator at the Raymond M. Alf Museum of Paleontology in California.
The team scrutinising the bumps and lumps on Triceratops skulls in museum collections. In particular they were looking for calluses associated with healed or healing fractures, and something called periosteal reactive bone which is the upshot of a superficial injury that pulls away the membrane that lines the outer surface of bones and leads to inflammation and then a scar on the bone.
They found the Triceratops' skulls were indeed peppered with scars, and the key to understanding what caused them came from their studies of a similar dinosaur called Centrosaurus, which had slightly different arrangement of horns to Triceratops. Instead of having one small horn on their nose and two big horns on each eye brow, the Centrosaurus had it the other way round, with one big horn on the end of their nose and two smaller ones above each eye.
It turned out that the Triceratops had 10 times more wounds than Centrosaurus, suggesting that Centrosaurus might have had a more passive, ornamental use for their horns while the Triceratops tussle was much more common.
Evidence that Triceratops did battle with each other comes from the fact that most of these battle scars were found on the large bone frill at the back of their skulls, the exact spot where their two long horns would have gauged if Triceratops had locked horns in battle perhaps a little like modern-day deer and antelope.
It seems unlikely that something else like a fungal infection caused these lesions because that would have led to similar patterns across all the skull bones rather than a concentration of lesions around the neck frill.
And it probably wasn't other predators that caused these injuries, since they would probably have attacked both Triceratops and Centrosaurus in a similar way.
This study was the first to look many different Triceratops specimens to try and understand what these incredible creatures got up to when they were still alive. And it seems that they may well have used their mighty appendages in a dinosaur brawl to work out who was the top Triceratops.