part of part of connects connects nasal cavity nasopharynx cranium posterior nasal aperture http://upload.wikimedia.org/wikipedia/commons/8/87/Gray855.png VHOG:0000545 posterior choana choana nasopharyngeal naris XAO:0000277 Wikipedia:Posterior_nasal_apertures internal naris MA:0001323 EHDAA:7842 Fish don't have choanae, instead they have two pairs of external nostrils EHDAA2:0000242 Opening/conduit between the nasal cavity and the nasopharynx[AAO] The choanae are separated by the vomer[WP]. posterior nasal apperture One of the paired openings from the nasal cavities into the pharynx. [Bemis_WE, Functional_Anatomy_of_the_Vertebrates:_An_Evolutionary_Perspective, Glossary_G-6, Grande_L, Liem_KF, Third_Edition_(2001)_Orlando_Fla.:_Harcourt_College_Publishers, Walker_WF][VHOG] Opening between the nasal cavity and the nasopharynx.[AAO] In addition to tetrapods, the lungfish has internal nostrils too. In tetrapods the exhalant nostril (choana) empties into the buccal cavity. choanae AAO:0000093 The choana, a unique 'internal nostril' opening from the nasal sac into the roof of the mouth, is a key part of the tetrapod (land vertebrate) respiratory system. It was the first component of the tetrapod body plan to evolve, well before the origin of limbs, and is therefore crucial to our understanding of the beginning of the fish-tetrapod transition. (...) Here we present new material of Kenichthys, a 395-million-year-old fossil fish from China, that provides direct evidence for the origin of the choana and establishes its homology: it is indeed a displaced posterior external nostril that, during a brief transitional stage illustrated by Kenichthys, separated the maxilla from the premaxilla.[well established][VHOG] FMA:53143 EMAPA:17849 UBERON:0004771 posterior naris SCTID:244507001 internal naris