March 14 2018

12:00 158 HH

Deborah Bird
Ecology and Evolutionary Biology, UCLA

Olfaction written in bone: Clues to the mammalian sense of smell found in cribriform plate morphology


Nearly every mammal relies on smell for survival. One clue to the evolution of mammalian olfaction lies deep within the skull in a small, cryptic, perforated bone that separates snout from brain called the cribriform plate (CP). The perforations in the CP bone form early in development to surround assembling olfactory nerves and so provide a high-fidelity imprint of relative olfactory innervation within an adult animal’s snout. CP morphology varies widely across species and may be an informative proxy for olfactory capacity, applicable to living and extinct mammals. To test this, I used CT scans and 3D imaging to analyze relative CP size of over 50 species in the context of habitat, behavior, and olfactory genomics. Results showed that within Carnivora, aquatic species that forage underwater “noseblind,” without odorant cues, have smaller CPs than their terrestrial cousins. Moreover, within these aquatics, the deepest and longest diving pinnipeds have the smallest CPs, suggesting that the pressures of secondary adaptation to life underwater, especially at depth, has favored the loss of olfactory capacity and morphology. Finally, we found that across all mammalian superorders, from dolphin to elephant, CP size correlates closely with the size of olfactory receptor (OR) gene repertoires. This correlation allowed us to predict the likely OR gene repertoire of an extinct mammal, the sabertooth cat (Smilodon fatalis) from its preserved CP. This research places the cribriform plate at the intersection of olfactory genomics, development, and evolution.

Host: Blaire Van Valkenburgh
































































































































































































































































































































































































































































































































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