Twin Butterflyfish, Prognathodes geminus Copus, Pyle, Greene & Randall 2019

Prognathodes geminus from Holmes Reef, in the Coral Sea off Queensland, depth 140 m. Source: Fenton Walsh / Cairns Marine. License: All rights reserved

A whitish butterflyfish with three broad dark brown bands that taper ventrally, the first intersecting the eye, orange-brown pelvic fins, and an orange-brown rear margin on the soft dorsal and anal fins, and across the caudal peduncle.

Cite this page as:
Bray, D.J. 2022, Prognathodes geminus in Fishes of Australia, accessed 27 Mar 2023,

Twin Butterflyfish, Prognathodes geminus Copus, Pyle, Greene & Randall 2019

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Holmes Reef in the Coral Sea, depth 140 m. Elsewhere the species occurs in New Caledonia and Palau. In Palau, the species was seen around limestone outcroppings on steep slopes at depths of 110–150 m. The type specimens were collected in an area with broken limestone rubble.


Dorsal fin XIII,17-19; Anal fin III,15; Pectoral fin 15; Pelvic rays I,5; Caudal fin (principal branched rays) 15; Lateral line (pored scales) 26-27; Scale rows above lateral line to origin of dorsal fin 10-11; Scale rows below lateral line to origin of anal fin 20-21; Gill rakers (upper limb) 5-6, lower limb 10; Vertebrae 24.
Body deep, depth 1.71-1.76 in SL, compressed.


In life: Body white with three dark brown bands, the first beginning narrowly at origin of dorsal fin, curving slightly as it passes, mostly one-half eye diameter in width, to eye; second band originating at tips of third to fifth dorsal spines and basal half of fifth spine, crossing body ventrally, progressively narrower below lateral line to end on mid-abdomen one-half eye diameter in width; third dark brown band originating from outer third of eighth dorsal spine and tip of first two soft rays of fin, passing obliquely, equal in width, to lateral line, then narrowing to half that width at mid-base of soft portion of anal fin, and crossing fin to end on outer half of third anal spine; a yellowish brown bar, one-half eye diameter in average width (narrowing gradually to mid-peduncle depth), across caudal peduncle and base of caudal fin; remainder of caudal fin whitish; a yellowish brown band of pupil width passing obliquely from eye, narrowing on its anterior half, to end at tip of snout; eye silvery white with an oblique dark brown band in alignment with nape band across eye, the dorsal part half-pupil width, and the ventral part one-half that; opercular membrane bright yellow; margin of soft portion of anal fin dark yellowish brown, about pupil width on last rays and membranes, progressively narrower to first rays; a similar terminal margin on dorsal fin; pectoral fins translucent with a semicircular light gray bar at base, preceded on upper half by a bright yellow bar. about half-pupil diameter in width, in alignment with yellow margin of operculum; spine and first ray of pelvic fins white, the white continuing progressively shorter on remaining rays that are dark orange-yellow, the membranes translucent dark yellowish.


The specific name is from the Latin geminus (= twin), in reference to its similarity in colour to Prognathodes basabei from the Hawaiian Islands. 

Species Citation

Prognathodes geminus Copus, Pyle, Greene & Randall 2019, ZooKeys 835: 127, Figs. 1-3. Type locality: Ngemelis Island, northwest side, "Blue Holes", Palau, Caroline Islands, 7.13791N, 134.22181E, depth 116 m.


Bray, D.J. 2022


Atlas of Living Australia

Twin Butterflyfish, Prognathodes geminus Copus, Pyle, Greene & Randall 2019


Copus, J.M., Pyle, R.L., Greene, B.D. & Randall, J.E. 2019. Prognathodes geminus, a new species of butterflyfish (Teleostei, Chaetodontidae) from Palau. ZooKeys 835: 125-137.

Quick Facts

CAAB Code:37365098

Depth:110-150 m

Habitat:Reef associated

Max Size:7 cm SL

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