Abstract:
The ostrich hyobranchial apparatus consists of the centrally positioned paraglossalia and
basiurohyale and paired caudo-lateral elements (horns), each consisting of the
ceratobranchiale and epibranchiale. The paraglossalia lie within the tongue parenchyma and
consist of paired, flat, caudo-laterally directed cartilages joined rostrally. The basiurohyale
forms a single dorso-ventrally flattened unit composed of an octagonal-shaped body from
which extend rostral (the rostral process) and caudal (the urohyale) projections. The laryngeal
skeleton consists of cricoid, procricoid and paired arytenoid cartilages. The large ring-shaped
cricoid cartilage displays a body and paired wings which articulate with each other and with
the procricoid. The blunt, ossified, rostral projection of the cricoid and the scalloped nature of
the arytenoid cartilages are unique to the ostrich. The procricoid is a single structure which
links the paired arytenoids and wings of the cricoid. The hyobranchial apparatus is firmly
attached to the tongue parenchyma and to the larynx and proximal trachea. In contrast to
previous reports in this species, the horns of the hyobranchial apparatus are not related to the
skull. Ossification of the body of the basihyale, the ceratobranchials and the rostral process
and body of the cricoid cartilage of the larynx lends stability to these structures.
