Strong linear correlation between cribriform plate (CP) surface area (perforate area) and cumulative cross-sectional area of the CP foramina (log-log) (r2 = 0.91, P < 0.0001, n = 19).

The more exacting metric of total CP foramina area, representing the imprint of olfactory axon bundles in the ethmoid bone, serves to validate CP surface area as a metric of relative olfactory innervation. CP surface area is the preferable metric for future studies, as it is easily quantifiable, even in skulls with some CP damage, such as fossils. CP surface area was measurable here in 26 sample species, while foramina area was measurable in only 19 species. Image on y axis: taken from figure S3. Images on the x axis: left, section of CP bone (red) with splines, (rings of coordinate points), assigned to the perimeters of several foramina in Mimics; right, imaging software Rhinoceros creates non-planar surfaces from the splines, and surface areas of foramina are calculated and tallied.