If you look at enough dinosaur fossils, you’ll see that their skulls sport an amazing variety of bony ornaments, ranging from the horns of Triceratops and the mohawk-like crests of hadrosaurs to the bumps and knobs covering the head of Tyrannosaurus rex.
But paleontologists are increasingly finding evidence that dinosaurs had even more elaborate head ornaments not preserved with the fossil skulls — structures made of keratin, the stuff of fingernails, that were likely used as visual signals or semaphores to others of their kind.
A newly described species of dome-headed dinosaur — a pachycephalosaur dating from around 68 million years ago — is the latest example. Pachycephalosaurs lived during the Cretaceous period, between about 130 and 66 million years ago, and tended to be small-to-medium-sized plant eaters. Ranging from 3 to 15 feet long, they walked on two legs and had a long, stiff tail for balance.
The new species is based on a partial pachycephalosaur skull, including its bowling-ball shaped dome, that was unearthed in 2011 in the Hell Creek Formation in Montana, which are layers of Upper Cretaceous rock from which paleontologists have collected dinosaur fossils for decades.
Based on CT scans and microscopic analyses of slices through the fossilized dome, paleontologists Mark Goodwin of the University of California, Berkeley, and John “Jack” Horner of Chapman University in Orange, California, concluded that the skull likely had sported bristles of keratin, reminiscent of a brush cut.
“We don’t know the exact shape of what was covering the dome, but it had this vertical component that we interpret as covered with keratin,” Goodwin said, noting that a bristly, flat-topped covering “biologically makes sense. Animals change or use certain features, particularly on the skull, for multiple functions — it could be for display or for social and biological interactions involving visual communication.”
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