Much like a peacock flaunts its brightly colored tail, ancient Triceratops would have used their massive horns to attract mates, a new study suggests.

Image credits: Nobu Tamura / Wikipedia.

Despite its ferocious appearance, the triceratops was a gentle, herbivorous giant. This dinosaur emerged during the late Cretaceous, some 68 million years ago, being one of the last known genera of dinosaurs (not considering birds, which are still technically dinosaurs). The most noticeable features of the triceratops are the armored frill and the three horns on its head. Paleontologists have long debated and speculated on the purpose of these features.

For starters, it seems very plausible that they served as an armor and defense, as was first proposed more than 100 years ago by amateur paleontologist C. H. Sternberg. There’s some evidence supporting this theory: researchers have found fossil evidence of battles between triceratops and tyrannosaurs, with the triceratops coming on top despite suffering serious wounds. But most paleontologists believe that while the triceratops got in a scrap every now and then, defense wasn’t the principal purpose of these features.

Some scientists have proposed that triceratops males locked horns with each other in a duel, fighting over the right to mate with females. However, there’s not much in the fossil record to support this theory. Another idea is that the horns were used to differentiate between species — it’s not always easy to tell if someone is the same species as you, and no one really wants to waste time and effort only to mate with the wrong species. However, a new study found this isn’t really the case.

“We find no support for the hypothesis that sympatry correlates with higher ornament divergence in ceratopsian dinosaurs,” the authors wrote in the recent study published in Proceedings of the Royal Society B.

So if it’s not defense, it’s not for duels, and it’s not for identifying your species… what’s left? Well, as it’s so often the case in the biological world, the one promising thing that’s left is sexual advertising. In other words, in this new study, researchers say triceratops grew horns to advertise their strength and good genes in an attempt to sway mates.

“Individuals are advertising their quality or genetic make-up,” explained Andrew Knapp, lead author of the research reports. “We see that in peacocks too, with their tail feathers.”

They also found that both males and females had similarly developed horns, which is impressive in itself — although it’s always hard to discuss an animal’s behavior from fossils alone, this says quite a bit about their behavior, indicating similar lifestyles between males and females.

“Possibly they’re both quite invested in raising their young, like we see in birds,” concluded Mr. Knapp.

Journal Reference: Andrew Knapp, Robert J. Knell, Andrew A. Farke, Mark A. Loewen, David W. E. Hone. Patterns of divergence in the morphology of ceratopsian dinosaurs: sympatry is not a driver of ornament evolution. DOI: 10.1098/rspb.2018.0312