An embryonic fissure between the otic capsule and the arches which develop into the occipital bones. The fissure may persist into adulthood. It is also referred to as the 'lateral otic fissure' The metotic fissure opens into the vestibular fontanelle, if the fontanelle is present. (Johanson et al. (2003)). Otherwise it opens to the metotic foramen. [ http://palaeos.com/vertebrates/glossary/glossaryM.html ]