Data from: Olfaction written in bone: cribriform plate size parallels olfactory receptor gene repertoires in Mammalia

The evolution of mammalian olfaction is manifested in a remarkable
diversity of gene repertoires, neuroanatomy, and skull morphology across
living species. Olfactory receptor genes (ORG), which initiate the
conversion of odorant molecules into odor perceptions and help an animal
resolve the olfactory world, range in number from a mere handful to
several thousand genes across species. Within the snout, each of these
ORGs is exclusively expressed by a discrete population of olfactory
sensory neurons (OSN), suggesting that newly evolved ORGs may be coupled
with new OSN populations in the nasal epithelium. Because OSNs axon
bundles leave high-fidelity perforations (foramina) in the bone as they
traverse the cribriform plate (CP) to reach the brain, we predicted that
taxa with larger ORG repertoires would have proportionately expanded
footprints in the CP foramina. Previous work found a correlation between
ORG number and absolute CP size that disappeared when body size effects
were accounted for. Using updated, digital measurement data from
high-resolution CT scans and reexamining the relationship between CP and
body size, we report a striking linear correlation between relative CP
area and number of functional ORGs across species from all mammalian
superorders. This correlation suggests strong developmental links in the
olfactory pathway between genes, neurons, and skull morphology.
Furthermore, because ORG number is linked to olfactory discriminatory
function, this correlation supports relative CP size as a viable metric
for inferring olfactory capacity across modern and extinct species. By
quantifying CP area from a fossil sabertooth cat (Smilodon fatalis) we
predicted a likely ORG repertoire for this extinct felid.