Table 3.

Summary of the developmental process of the sphenoid during the embryonic period.

CS	Summary
17	The orbitosphenoid (OS) appears first, followed by the basisphenoid (BS)
18	OS and BS have stronger cellular condensation The presphenoid (PS) and alar process (AP) develop from the anterior and the back lateral of BS, respectively Mesenchymal cells around the maxillary nerve begin to proliferate (ala temporalis [AT] condensation)
19	An unclear condensation of the mesethmoid (ME) appears in front of PS The foramen rotundum (FR) begins to develop as a bottom half-completed hole within AT Cartilaginous matrix and perichondrium are little formed at this stage Almost all elements still do not have connections with each other
20	OS bends and begins to wrap around the optic nerve to form the optic canal PS fuses in the middle and continues to ME OS and BS have cartilaginous matrix and perichondrium Most elements connect with each other
21	In a few specimens, the medial pterygoid process (MP) develops from the inferomedial of AT FR completes its entire hole ME extends longer toward anterior by connecting with the nasal septum All elements fuse each other, and the boundaries between them become invisible
22, 23	OS enlarges and bends along the optic nerve, and the optic canal is almost fully encircled The lateral part of the lesser wing appears as an unclear and sharp condensation outward from OS in some specimens MP extends longer toward the oral cavity Most elements have massive matrices and clear perichondrium