The news comes too late for Jurassic Park III, but palaeontologists may have got dinosaur nostrils all wrong. A new analysis of their closest living relatives brings the extinct animals' nostrils far further forward.

It's a hypothesis not to be sniffed at, according to its author Lawrence Witmer of Ohio University in Athens, Ohio. Nostril position could have affected many dinosaurs' biology, behaviour - and looks1.

Several dinosaur skulls have huge nasal cavities at the front, sometimes stretching up to the top. The animals' nostrils opened into this cavity somewhere along its length, but as soft tissues like skin and cartilage are not fossilized, nostril position is guesswork.

Witmer suspects that today's nostril misplacement originated about 150 years ago. Those studying the very first dinosaur skulls (from huge sauropods) thought that they were aquatic, and so placed the nostrils high on the animals' heads, like snorkels.

Although sauropods were later found to be mainly terrestrial, nostril position was never revised. Since then, says Witmer, "there has been no real scientific investigation into nostrils".

Witmer wants them moved forwards after having X-rayed skulls of dinosaurs' living descendents. He found that the nostrils of birds, crocodiles and other reptiles, such as turtles, are almost always 'rostral' - at the front of the nasal cavity. "We uncovered a very general phenomenon," he says.

It is unlikely that dinosaurs would have been any different, agrees Thomas Holtz, who works on the anatomy and behaviour of large dinosaurs at the University of Maryland in College Park.

What is surprising, says Holtz, is that "no one ever thought to link all this together before". The nasal cavities of living animals contain complicated tissues that are involved in smell - dictating how the animals find food and mates, and avoid predators - and control body temperature and water loss.

Dinosaurs' nasal cavities were thought to be important for the same reasons. "In almost all large dinosaurs there is some sort of expansion or elaboration of the nasal cavity," Holtz explains. But with the nostrils at the back, air would have gone straight down their windpipes, bypassing both smell and regulation of temperature and moisture.

Had early palaeontologists "ever stopped to think about where the air was coming in," they may have realized the error of their ways, argues Witmer.

Nosing around

Not all nostrils are on the move. Some dinosaurs have small nasal cavities that limit nostril location. Others, including the enormous Brachiosaurus, "have nasal cavities two feet long," says Witmer.

Who nose: nostril position in Tyrannosaurus rex Credit: © Science/Paintings by W. L. Parsons under the direction of L. M. Witmer

In these creatures and others such as Tyrannosaurus and Triceratops, bony grooves and protuberances, which probably carried nerves, blood vessels and cartilage, line the cavernous nasal cavities, hinting at nasal functions of similar complexity to those of modern vertebrates. Rostral nostrils would have channelled air over these tissues.

Long nasal cavities in large dinosaurs may have been particularly important in removing moisture from exhaled air, much as they are in today's mammals, says Holtz. With rostral nostrils, dinosaurs would have retained more moisture even when breathing heavily. "[This] could have allowed them to have a more continuously active, more advanced lifestyle," he says.

Morphometrician Ralph Chapman, who models dinosaurs for display at the National Museum of Natural History in Washington, D.C. is relieved by Witmer's findings. He has long suspected that some dinosaur nostrils, especially the sauropods, were in the wrong place. "They always looked really weird," he says.

Take your pick: Diplodocus shows off some new nostrils Credit: © Science/Paintings by M. W. Skrepnick under the direction of L. M. Witmer

Chapman's team has just finished building a Triceratops exhibit at the museum, the nostrils of which, he admits, may now be a bit far back. But he plans to wait and see what other palaeontologists make of Witmer's work before going to the effort and expense of giving all his big dinosaurs facelifts.