Fig. 1. Schematic diagram of the laterophysic system in butterflyfishes of the genus Chaetodon. This unique anatomical feature is a putative acoustico-lateralis hearing mechanism located at the junction of the trunk lateral line (TLL) and head lateral line (HLL) canal systems. The laterophysic connection is formed by gas-filled horns (H) that extend from the anterior swim bladder (SB) and a small tympanum (dark circle and X) on the medial edge of the canal in the supracleithrum bone (S). The swim bladder horns also project towards the otic capsule. Figure modified with permission from Webb and Smith (2000).