Many dinosaurs have enormous and complicated bony nasal apertures. Function
al interpretation requires knowledge of the Location of the external openin
g in the skin. Traditionally, the fleshy nostril of dinosaurs has been plac
ed in the back of the bony opening, but studies of extant dinosaur relative
s suggest that it is located far forward. Narial blood supply and cavernous
tissue corroborate the rostra[ position in dinosaurs. A rostra[ nostril wa
s, and remains, a virtually invariant rule of construction among Amniota, w
hich has consequences for (I) nasal airstreaming, and hence various physiol
ogical parameters, and (ii) the collection of behaviorally relevant circumo
ral odorants.