Prognathodes geminus is the newest species of butterflyfish from a genus that haunts the abyssal depths of the oceans. Closely related to Prognathodes guezei and P. basabei, the new ‘Gemini’ butterflyfish is so named for its very close resemblance to other members of Prognathodes – indeed it takes very careful analysis and observations to distinguish several member of this genus.
The Prognathodes butterflyfish are, when they are rarely available, a very popular group with rare fish collectors, not just for their scarcity but also for their bold coloration and appearance. The freshly minted Prognathodes geminus is superficially identical to the deepwater Hawaiian orange-fin butterflyfish P. basabei.
The only visibly discernible difference between P. geminus & P. basabei is the coloration of the 3rd dorsal spine, being blackish brown in P. geminus and whitish cream in P. basabei. But genetically the difference between these two similar looking species is more divergent than between humans and chimpanzees.
The new Geminus or Gem butterflyfish was discovered in Palau at the bone-crushing depth of 116 meters, which is 380 feet, or more than double the safe limit for recreational SCUBA. The Gem butterflyfish was collected alongside the fabled Chromis abyssus and Abei angelfish and is documented in a famous 2007 deep diving video from National Geographic. The spankin’ new Prognathodes is described by Copus et. al. 2019 in the latest edition of ZooKeys.