Dinosaurs evolved fancy head gear to woo mates, but it had an unintended consequence

Crowns fit for a queen.
Crowns fit for a queen.
Image: DariuszSankowski/Pixabay/CC.0-Public Domain
We may earn a commission from links on this page.

You probably wouldn’t have missed the largest dinosaurs roaming Earth during the Jurassic period about 150 million years ago. These theropods walked on two feet, often weighed about as much or more than a small car, and in some cases were 40 ft long and 12 ft tall.

But just in case their size didn’t announce their presence, you definitely would have noticed their fancy bony crowns.

On Tuesday (Sept. 27), researchers from North Carolina State University published a paper describing a trend they noticed among these Jurassic giants: the larger they were, the bigger the headgear. They believe that these bony cranial structures may have actually been one of the reasons that these dinosaurs got so big. Selective evolutionary pressure may have made it so that the largest theropods, with the prettiest head decor, mostly bred with each other, perpetuating the trait.

In the study, researchers looked for a relationship between dinosaur body size and head decoration. They studied evolution pattern of 111 different species of theropods—which includes animals like T. Rex and something called a Giganotosaurus—through fossil records. They found that 20 of the 22 largest theropods had large head decorations. Dinosaurs without these head ornaments, were much less likely to be over 2,200 lbs. Furthermore, based on evolutionary rates, it looks like once these well-decorated dinos developed their crowns, their evolutionary trend towards being bigger sped up.

Although it’s hard to exactly decipher what evolution intended through fossil records, modern animal traits seem to back up the theory that ornamental traits can be advantageous. Colorful plumage in birds and different kinds of head and throat decorations (paywall) in modern lizards also evolved as a result of breeding pressure. These traits helps animals catch the eye of a potential mate, warn predators of their potency, or mark their territory.

One theory the North Carolina researchers postulate is that ornamental head structures would be visible in open plains to find a partner. In tree-crowded forests, even with head decorations would be less visible anyway, and there would be no need to evolve flashy crowns.