Otic vesicle the lateral side will be paraxial mesoderm. Neural crest cells will migrate rostral and caudal to the placode. The general sequence in formation of the otic vesicle is relatively conserved across vertebrates, although there is much variation in timing and stages. Patterning during morphogenesis into the distinctive inner ear structures is determined by homeobox transcription factors including PAX2, DLX5 and DLX6, with the former specifying for ventral otic vesicle derived auditory structures and the latter two specifying for dorsal vestibular structures. The otic vesicle is derived from the cranial placode. The early otic vesicle is characterized as having broad competence
Otic notch Otic notch Otic notches are invaginations in the posterior margin of the skull roof, one behind each orbit. Such notches are found in labyrinthodonts and some of their immediate ancestors, but not in their reptilian descendants. The presence or absence of the otic notches is one of the traits used to separate the amniotes from the amphibian grade tetrapods. The notches have been interpreted as part of an auditory structure and are often reconstructed as holding a tympanum similar to those seen in modern anurans. Analysis of the "columella" (the stapes in amphibians and reptiles) of labyrinthodonts however indicates that