SEM micrographs of alligator nasal epithelia. A Fracture of olfactory epithelium in zone 5. With 70 μm this is one of the thinner regions of epithelium on the caudal turbinate. B Overview of nasal epithelium in zone 1 which TEM preparations proved to be olfactory. Arrowheads depict openings of Bowman glands. C Fracture showing the apical portion of olfactory epithelium in zone 4. The olfactory knob of an OSN bears cilia and microvilli whereas the apical surfaces of the supporting cells (SC) are covered by microvilli. D Overview of olfactory epithelium in zone 5 showing the "mixed" olfactory knobs bearing cilia and microvilli (*). Note that the cilia do not taper at their ends. The short microvilli of supporting cells are visible between the olfactory knobs. E Overview of nasal epithelium in zone 4. A dense population of ciliated nonsensory cells (compare Fig. 4D) covers the more ventrally located surface. Only occasionally, non-ciliated cells are interspersed (*). F Overview of olfactory epithelium in zone 5. Between the cilia of OSNs and supporting cells (distinguishable by their short microvilli), one thick dome-shaped apical ending indicates the presence of a SCC (arrow).