Olfactory region of the brain and olfaction in Theropoda

In an ongoing study, we are examining the region of the brain associated with the sense of smell (olfactory region) in non-avian theropods and other archosaurs, and studying its evolution among Theropoda. Our studies establish homologies in the olfactory region of the braincase among crocodiles, dinosaurs, and birds, and reconstruct the position of the olfactory bulbs (anterior part of the forebrain associated with the sense of smell) in dinosaurs.

We show that theropod dinosaurs have a range of olfactory bulb sizes relative to brain and body size and that dromaeosaurids and tyrannosaurids have the largest olfactory bulbs among 20 species of theropods, suggesting a keener sense of smell in these taxa than in other theropods. 

ornithomimd skull

CT Rendering of ornithomimd skull.

ornithomimd skull

Cutaway showing regions of the brain. Olfactory bulbs in red. Images courtesy Y. Kobayashi.

References:

Ali, F., Zelenitsky, D.K., Therrien, F., and Weishampel, D.B. 2008. Homology of the “ethmoid complex” of tyrannosaurids and its implication for the reconstruction of the olfactory apparatus of non-avian theropods. Journal of Vertebrate Paleontology. 28, 123-133.

Zelenitsky, D.K., Therrien, F., and Kobayashi, Y. 2009. Olfactory acuity in theropods: palaeobiological and evolutionary implications. Proceedings of the Royal Society B: Biological Sciences. 276: 667-673.