A threebanded butterflyfish caught near Panama City, Panama (November 20, 2023).
Chaetodon humeralis has an oval disc-like body which is strongly compressed and it has a small mouth positioned at the end of a short snout. The colour of the body is white or silvery white with obvious brownish-black bands on the line of the pectoral fin and another running in from the base of the caudal fin, a third brownish-black band runs from the nape down through the eye to the throat. The median fins all have black bands through them.[2][3] There are 12–13 spines and 18–20 soft rays in the dorsal fin while the anal fin contains 3 spines and 15–17 soft rays. The maximum total length reached is 25.4 centimetres (10.0 in) but 12 centimetres (4.7 in) is more typical.[4]
Chaetodon humeralis is strongly associated with rock reefs but has been recorded over a variety of substrates in different parts of its range, including intertidal pools, mangroves and estuaries.[1] It is normally encountered in pairs or small shoals, often near the shore. It will mix in shoals with the Pacific spadefish (Chaetodipterus zonatus). It forms pairs to spawn,[4] laying pelagic eggs.[2] It feeds on benthic invertebrates and algae.[3] it has a depth range of 2 to 55 metres (6.6 to 180.4 ft) but is more common between 3 and 12 metres (9.8 and 39.4 ft).[1]
Chaetodon humeralis was first formally described in 1860 by the German-born British zoologist Albert Günther (1830–1914) with the type locality given as “the Sandwich Islands” in error for Central America.[5] Some authorities place this species within the nominate subgenus Chaetodon but others consider it to be incertae sedis.[6]
