First CT scans confirm lambeosaur brain capacity

Scientists used computers to fill in gaps in fossilized heads of the creatures.

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If there was an “America’s Next Top Model” competition for dinosaurs, the creatures called lambeosaurs would take first prize.

The heads of these duck-billed dinosaurs were adorned with elaborate crests of bone, arrayed in exotic variations – Elvis-like pompadours, swooping comma shapes, and things that resembled Napoleon’s cocked hat.

What were they there for? Over the years, researchers have suggested different purposes for the hollowed ridges. Long nasal passages snaked through them, so perhaps they boosted lambeosaurs’ smelling ability. Maybe they were a kind of snorkel for underwater breathing. Or a mechanism for cooling the blood.

Now, scientists who probed the lambeosaurs’ fossilized skulls with X-rays say the crests functioned like the brass tubing in a trombone. Their lengthy passages shaped and amplified the dinosaurs’ deep, bellowing calls, helping them communicate with each other.

The scans confirmed the crests’ role as a signaling device by showing that lambeosaurs had ear structures capable of detecting the calls, and a large enough brain to act on the information.

“The animals could both produce and hear the sounds,” and had the brainpower to process them, said Ohio University paleontologist Larry Witmer, who directed the first CT scans of lambeosaurs’ brain housings and inner ears.

The findings were presented Thursday at the Society of Vertebrate Paleontology’s annual meeting in Cleveland. Scientists attending the conference saw vivid 3-D computer models of the dinosaurs’ skulls, highlighted with lilac-colored brains, bubblegum-pink inner ears, and tubular, lime-green nasal passages twisting around inside the hollow head crests.

“It’s beautiful work that answers important questions,” said Michael Ryan, the curator of vertebrate paleontology at the Cleveland Museum of Natural History, who was not a part of the study.

Unlike bone, the soft tissue of brains and inner ears decays and isn’t preserved in fossils. The scientists used computer software to digitally fill in the spaces in the skull those organs would have occupied, guided by impressions the tissue left in bone. The images are called virtual endocasts. In the last few years the technique has revolutionized paleontology.

Although the endocasts revealed that lambeosaurs had relatively big brains – about the size of a soda can — the portion called the olfactory bulbs devoted to smelling was small compared to dinosaurs that didn’t have the crests. If the lambeosaurs were using the greater surface area of their long, convoluted nasal passages as a way of heightening their sense of smell, their olfactory bulbs should have reflected that, and they didn’t.

“That’s the final nail in the coffin” for the theory that the crests played a role in helping lambeosaurs smell more acutely, said David Evans, the study’s lead author and a paleontologist at Toronto’s Royal Ontario Museum.