Excerpt
Olfactory Region
Alary cartilage.—The anterior end of the alary cartilage (al. c., ) lies within the posterior concavity of the alary process (al. proc., ) of the premaxillary (pmax.). In posterior sections the cartilage assumes a dorsolateral position (), ventral and slightly lateral to the tectum nasi. The alary cartilage remains narrowly separated from the tectum nasi but fuses ventromedially with the septum nasi and forms a nearly complete cartilaginous capsule around the anterior end of the cavum principale. Posterior to the anterior end of the cavum medium and the lamina superior, the alary cartilage separates ventrally from the lamina. In subsequent posterior sections, the cartilage, arcuate in cross section, becomes progressively smaller and terminates at the level of the union of the medial and lateral recesses of the cavum inferior.
Prenasal cartilages.—The superior prenasal cartilage is small; it lies adjacent to the posterodorsal surface of the alary process of the premaxillary, and anterior to the alary cartilage. The inferior prenasal cartilage (inf. pnas. c., , ) appears posterior to the appearance of the alary cartilage. The anterior terminus lies at the base of the alary process; the cartilage extends dorsally () along the posterior surface of the alary process and then curves posterodorsally and joins the solum nasi medioventral to the posterior end of the septomaxillary ().
Tectum nasi.—The anterolateral corner of the tectum nasi (tect. nas., ) appears just posterior and dorsomedial to the anterior end of the alary cartilage. The anterior process is short; it fuses medially with the septum nasi forming a complete roof to the cavum principale (). The oblique cartilage (obl. c.) diverges laterally from the tectum nasi just posterior to the terminus of the alary cartilage (). Medially, the tectum nasi persists, overlaid by the nasal bone laterally.
Septum nasi.—Posterior to the appearance of the septum nasi (sept, nas.) and its union with the tectum nasi (), the septum abruptly expands across the width of the skull medial to the alary cartilage. The septum is entirely cartilaginous posterior to the level of the olfactory eminence, except for a small amount of secondary membranous ossification dorsomedially at a level anterior to the nasal bones. Perichondral ossification commences in the dorsal part of the septum nasi at the level of the olfactory eminence. Endochondral ossification first appears dorsally in the vertical part of the septum at the level of the internal nares. Ossification of dorsal parts of the septum precedes ossification of ventral parts. Perichondral ossification of the ventral part of the septum nasi is first noted at the level of transition between the planum antorbitale and solum nasi. Perichondral ossification gradually gives way to endochondral ossification posteriorly.
Fig. 1. Partially disarticulated skull (left frontoparietal and nasal removed) of Smilisca baudini, KU 68183, ♀ × 4....