part of part of in taxon surrounds surrounds Theria <mammals> ear dermatocranium tympanic cavity bony projection auditory bulla http://upload.wikimedia.org/wikipedia/commons/a/af/Toothed_whale_sound_production.png In extant primates, the structure is found in tarsiers, lemurs, and lorises[WP]. When present in marsupials, it usually forms the alisphenoid; in placentals variously constructed of ectotympanic, entotympanic, petrosal, or a combination of these and others UBERON:0008959 auditory bullae EMAPA:37433 tympanic bulla bulla A hollow bony structure on the ventral, posterior portion of the skull of placental mammals that encloses parts of the middle and inner ear. In most species, it is formed by the tympanic part of the temporal bone. NCIT:C112425 bulla tympanica Wikipedia:Auditory_bulla sigmoid process may be formed from entotympanic and ectotympanic