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Dino crests may have had communication role

Oct. 16, 2008
Courtesy NSF
and World Science staff

The strange, bony crests on the heads of the duck-billed di­no­saurs known as lam­be­o­saurs may have served for com­mu­nica­t­ion—both vo­cal and vis­u­al, ac­cord­ing to a new stu­dy.

The struc­tures con­tain ex­tremely long, con­vo­lut­ed na­sal pas­sages that loop up over the tops of their skulls. In the stu­dy, sci­en­tists used med­i­cal scans to peer in­side these crests and re­con­struct the brains and na­sal ca­vi­ties of four dif­fer­ent lam­be­o­saur spe­cies.

Reconstruction of the hel­met-crest­ed lam­be­o­saur Cor­y­tho­saur­us. (Cred­it: Mi­ch­ael Skrep­nick)

They an­nounced the find­ings Oct. 16 at the an­nu­al meet­ing of the So­ci­e­ty for Ver­te­brate Pa­le­on­tol­ogy in Cleve­land, Ohio.

“These sci­en­tists have used cutting-edge vis­u­al­iz­a­tion and re­con­struction tech­niques to show that duck-billed di­no­saurs likely com­mu­ni­cated via sound and sig­nal,” said Ad­am Sum­mers, pro­gram di­rec­tor in Di­vi­sion of In­te­gra­tive and Or­gan­is­mal Sys­tems at the U.S. Na­tional Sci­ence Founda­t­ion, which helped fund the re­search.

Some pa­le­on­tol­ogists have sug­gested that the crests height­ened the sense of smell. Oth­ers have ar­gued that they reg­u­lat­ed tem­per­a­ture; still oth­ers, that they acted as sound res­onators for com­mu­nica­t­ion.

“The shape of the brain can tell us a lot about what senses were im­por­tant in a di­nosaur’s eve­ry­day life, and give in­sight in­to the func­tion of the crests,” said Da­vid Ev­ans, a pa­le­on­tolo­g­ist at the Roy­al On­tar­i­o Mu­se­um and the Uni­ver­s­ity of To­ron­to.

“It’s dif­fi­cult to in­fer the func­tion of struc­tures in an ex­tinct di­no­saur when there is so lit­tle re­sem­blance to any liv­ing an­i­mal,” said Jack Horner, a mem­ber of the re­search team and pa­le­on­tolo­g­ist at Mon­tana State Uni­ver­s­ity. 

CT scan reconstruc­tions of Co­ry­tho­saur­us; the na­sal cavity is green, and the brain pur­ple. (Cour­tesy Wit­mer & Rid­gely, Ohio U.)

By us­ing and an­a­lyz­ing the scans, the sci­en­tists said they were able to cir­cum­vent the prob­lems. “Even though the soft tis­sues are not pre­served in the fos­sils, the shape of the bones that en­case the brain and na­sal pas­sages are,” said Ev­ans. “From there, the anat­o­my of these mis­sing soft parts is easily in­ter­pret­ed.”

The scan re­sults re­vealed a mis­match be­tween the ex­ter­nal shape of the crest and the in­ter­nal shape of the na­sal pas­sages in closely re­lat­ed spe­cies, sug­gest­ing a spe­cial func­tion for the na­sal ca­vity, the in­ves­ti­ga­tors said. 

The part of the brain re­spon­si­ble for smell was rather small and prim­i­tive, they added, in­di­cat­ing the crest did­n’t serve to im­prove that sense.

Com­put­er mod­els done by oth­er re­search­ers sug­gest that the crests could have been used to make low, ee­rie bel­low­ing calls that could have been used in com­mu­nica­t­ion, per­haps to call for mates or warn oth­ers of preda­tors.

The new study used used CT, or com­put­ed to­mog­ra­phy, scans, a meth­od of ex­am­in­ing ob­jects with X-rays and a com­put­er that builds a se­ries of cross-sec­tion­al scans. 

The scans doc­u­mented a del­i­cate in­ner ear that con­firms that the di­no­saurs could hear the low calls pro­duced by the crest, said Wit­mer. “We were sur­prised to see just how large the cen­ters of the brain as­so­ci­at­ed with high­er cog­ni­tive func­tions were,” he added. “We sus­pected that the crest­ed duck-billed di­no­saurs used both vo­cal and vis­u­al dis­plays, but now we see that they had the brain pow­er and hear­ing to pull off these be­hav­iors.”

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The strange, bony crests on the heads of the duck-billed dinosaurs known as lambeosaurs may have served for communication—both vocal and visual, according to a new study. The structures contain extremely long, convoluted nasal passages that loop up over the tops of their skulls. In the study, scientists used CT-scanning to look inside these crests and reconstruct the brains and nasal cavities of four different lambeosaur species. They announced the findings Oct. 16 at the annual meeting of the Society for Vertebrate Paleontology in Cleveland, Ohio. “These scientists have used cutting-edge visualization and reconstruction techniques to show that duck-billed dinosaurs likely communicated via sound and signal, “ said Adam Summers, program director in Division of Integrative and Organismal Systems at the U.S. National Science Foundation, which helped fund the research. Some paleontologists have suggested that the crests heightened the sense of smell by increasing the surface area of the sensory tissue. Others have argued that they regulated temperature, and still others have speculated that the crests acted as sound resonators for communication. “The shape of the brain can tell us a lot about what senses were important in a dinosaur’s everyday life, and give insight into the function of the crests,” said David Evans, a paleontologist at the Royal Ontario Museum and the University of Toronto. “It’s difficult to infer the function of structures in an extinct dinosaur when there is so little resemblance to any living animal,” said Jack Horner, a member of the team and paleontologist at Montana State University. By using and analyzing the scans, the scientists said they were able to circumvent the problems. “Even though the soft tissues are not preserved in the fossils, the shape of the bones that encase the brain and nasal passages are,” said Evans. “From there, the anatomy of these missing soft parts is easily interpreted.” The scan results revealed a mismatch between the external shape of the crest and the internal shape of the nasal passages in closely related species, suggesting a special function for the nasal cavity, the investigators said. The part of the brain responsible for smell was relatively small and primitive, indicating the crest didn’t serve to improve that sense. Computer models done by other researchers suggest that the crests could have been used to make low, eerie bellowing calls that could have been used in communication, perhaps to call for mates or warn others of predators. The CT scans documented a delicate inner ear that confirms that the dinosaurs could hear the low calls produced by the crest, said Witmer. “We were surprised to see just how large the centers of the brain associated with higher cognitive functions were,” said Witmer. “We suspected that the crested duck-billed dinosaurs used both vocal and visual displays, but now we see that they had the brain power and hearing to pull off these behaviors.”