Paleo-Pinocchios - dinosaur noses were quite large - Brief Article

Everything about dinosaurs was oversize, even their noses. Many of the brutes--including the rhinolike Triceratops--had nasal cavities that took up half their skulls. New studies suggest the reason for those king-size honkers. They probably served as air conditioners that kept the dinosaurs' brains from overheating, says evolutionary biologist Lawrence Witmer of the Ohio University College of Osteopathic Medicine in Athens.

Large animals have a hard time cooling down, because their skin surface area is small relative to their body volume. If internal temperatures rise too high, vital organs like the brain can suffer damage. When dinosaurs ruled the Earth, the global climate was much warmer than it is today. Overheating might have been a constant threat under the Mesozoic sun.

Modern mammals, birds, and reptiles normally stave off heat stroke with the help of structures in the nose called nasal conchae, sheets of mucous membrane that vastly increase the surface area over which air passes. As blood flows through a thick mesh of vessels in the conchae, heat transfers to the air; the cooled blood ultimately brings down the temperature in the brain. Witmer and his colleagues in the DinoNose project examined dinosaur skulls using medical CT scanners and found similar nasal conchae in large, big-nosed dinosaurs but not in their smaller, more primitive cousins. Without these structures, Witmer says, dinosaurs might not have been able to thrive at such tremendous sizes.

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