Australasian Science: Australia's authority on science since 1938

A Dinosaur with a Cock’s Comb

By Stephen Luntz

The first evidence of a fleshy crest on a dinosaur has been compared to the comb on modern birds such as roosters.

“It’s very rare for skin to fossilise,” says Dr Phil Bell of the University of New England’s School of Earth Sciences. “You need very unusual conditions. An animal must have been buried rapidly after it died, within 1–2 days, and the chemical conditions need to be just right. Even when this happens, skin is often overlooked in the field because it is so un­expected and delicate and thin.”

Edmontosaurus was the most common dinosaur in North America 75–65 million years ago. The bones of the herbivorous hadrosaur, growing to 12 metres long, have been heavily studied but Bell’s discovery of some skin from the head was entirely new.

Bell made the discovery at an established dig site in Alberta, Canada. A block that had fallen from a neighbouring cliff contained the back part of the dinosaur’s skull as well as the neck and first few vertebrae, but far more significantly the whole crest was also included.

The skull was around 1 metre in length, while the crest is just 30 cm long and 20 cm high. Bell thinks that the crest may have been a device to show off to mates, just like in chickens, or possibly to deter rivals.

Edmontosaurus was highly social, living in groups of several dozen individuals. “Clearly there would have been a hierarchy,” Bell says. It is possible the crest played some role in this.

“In some related species, bony protuberances have been found and these can be as large as the skull, with branches and hollow passages connected to the nose to amplify sound,” says Bell.

But this comb is not connected to the nasal passages. It is also too small to be an energy reservoir like a camel’s hump. While Bell speculates that “the biggest, brightest, flashiest crest got the girls,” its small size raises the possibility that the individual in question was a female, since in many species of birds the females have smaller versions of the comb.

“Sexing an extinct animal is hard,” Bell notes. “In only a few species of dinosaurs can we tell the males from the females.”