The present study deals with a complete description of the neurocranium of two developmental stages ( 24 and 28 mm. total body length embryos ), of Hirundo rustica savignii. Each of the nasal and interorbital septa is developed from the dorsal edge of the intertrabecular bar without isolated centers of chondrification. But the paranasal cartilage has an isolated center of chondrification. Also, the parietotectal cartilage develops from the dorsal edge of the nasal septum. The paranasal and parietotectal cartilages share in the formation of paries lateralis nasi.
The formation of the nasal capsule is completed through the occurrence of side walls (paries lateralis nasi and planum antorbitale), roof ( parietotectal cartilage ), one concha only (maxilloturbinal cartilage ) and the nasal serptum which divides the nasal region into two capsules.
The anterior orbital cartilages begin to suffer from the regression process, and there is no connection between the two orbital cartilages (anterior and posterior).
The interorbital septum is highly developed to separate between the two orbital capsules.
The acrochordal cartilage starts to regress and the barrier between it and the basal plate.
There are some fenestrations such as the hypophyseal fenestra, the oval fenestra, perilymphatic foramen, endolymphatic foramen and the fissure metotica divided into three foramina.
There are only seven prominentiae on the outer surface of the auditory capsule. Also there is differentiation between the cochlear and canalicular portions after their union.
The metotiv cartilage has two centers of chondrification, the first one from the basal plate and the other one has a separate center since the metotic cartilage forms the floor of the auditory capsule.
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