Bicolor butterflyfish (Prognathodes dichrous)

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Chordata · Class: Teleostei · Order: Acanthuriformes · Family: Chaetodontidae · Genus: Prognathodes.

Accepted name: Prognathodes dichrous · Authority: (Günther, 1869) · Taxonomic status: accepted · AphiaID: 273373.

Synonyms and superseded combinations recorded for this taxon: Chaetodon dichrous Günther, 1869.

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=273373 (CC BY 4.0). Accessed 2026-09-23.

Biology and life history (FishBase)

Measured values published by FishBase for Prognathodes dichrous. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.

Maximum length: 16 cm · Depth range: 3–120 m · Habitat zone: reef-associated · Body shape: short and / or deep · Vulnerability index: 10 of 100 · Fishery importance: commercial · Aquarium trade: commercial.

FishBase notes: Occasionally encountered in shallower water in caves or at the bases of overhangs (Ref. 5288). Also occurs on seamounts (Ref. 057925). Usually occur in pairs, which browse over the rocky substratum in search of benthic invertebrates. Unknown to marine aquarium enthusiasts (Ref. 4858). Oviparous (Ref. 205). Form pairs during breeding (Ref. 205).

Source: FishBase species summary (SpecCode 12263) — https://www.fishbase.se/summary/Prognathodes-dichrous.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-23.

Conservation status (IUCN Red List)

The IUCN Red List assesses Prognathodes dichrous (Günther, 1869) as Least Concern (code LC). No trend, population estimate or threat analysis is given here, because none is available from this source without the Red List API; follow the source link for the full assessment, including its date.

Source: IUCN Red List of Threatened Species (taxon 165690) — https://www.iucnredlist.org/species/165690/0; GBIF IUCN Red List category endpoint (taxonKey 2385618) — https://api.gbif.org/v1/species/2385618/iucnRedListCategory. Accessed 2026-09-23.

Description and natural history (Wikipedia)

Prognathodes dichrous is largely brown in colour with the upper rear quarter of the body being white, including the dorsal and caudal fin The dorsal fin contains 12 spines and 19 soft rays while the anal fin has 3 spines and 15 soft rays. This species attains a maximum total length of 16 cm. There is a white eye ring, too.

Prognathodes dichrous is found in the southeastern Atlantic Ocean where it is endemic to the waters around the British Overseas Territories of Ascension and Saint Helena islands.

Prognathodes dichrous is a species of deeper water, normally found between 12 and 35 m but ar Hummock Point it can be seen in water as shallow as 1 m. It is found in caves and under overhangs, as well as on seamounts. It is normally encountered in pairs, although shoals have also been recorded, which browse on benthic invertebrates over rocky areas. This is an oviparous species which spawns as pairs.

Prognathodes dichrous was first formally described in 1869 by the German-born British zoologist Albert Günther (1830–1914) with the type locality given as St Helena. Its closest relative appears to be the rather similar Prognathodes obliquus which is endemic to St Paul Rocks off Brazil.

Source: Wikipedia: Prognathodes dichrous — https://en.wikipedia.org/wiki/Prognathodes_dichrous (CC BY-SA 4.0). Accessed 2026-09-23.