“I DO THINK THERE’S A REALLY INTERESTING STORY HERE, BUT WE DON’T QUITE KNOW WHAT IT IS” - Ian Tattersall
We know what species these are, we're just not sure of the genus. So far this has been referred to, in order, as Epiplatys, Aphyosemion and Episemion. Paradoxically, it is more closely related to Diapteron per Sonnenberg's 2006 DNA analysis.
In 1983 Herve Gonin in North Gabon collected these fish in the Ottominan stream near Medouneu and although the species was not at the time described, but the existence of two different types was noted.
In 1986, 6kms south of Bibassé CAT was collected from a steam in January 10, during the BWW 86 expedition, their location 20.
1987 Radda and Purzl explored the Mont de Cristal region of North Gabon in and found CAT in the Woleu/Rio Benito System on the road from Oyem to Mitzic which they described as Epiplatys callipteron.
The holotype for CAT is shown in Radda's photo. Another, and considered to be at the time just an aberrant form of CAT, was mentioned by Gonin, prior to 1995. In August of 1999 Blum, Bitter and Sewer, collected another fish, different from CAT, from the two BBS expidition locations: 22 and 23. In 2002 Blum, Fleck, & Sonnenberg collected a holotype and three paratopotypes at location 23 (referred to as G 02/157 in their journal and in 2006 Sonnenberg, Blum & Misof collected and Episemion krystallnorum was described. Molecular evidence shows these fish are closest to Diapteron even though they look like an Epiplatys and their taxonomy is muddled. There is no "wrong" name for these fish at present because we don't know what the right one is. Here are some of the possible ones: Aphyosemion callipteron, Episemion callipteron, Aphysemion (Episemion) callipteron and Episemion callipteron [Apyosemion].
First collected on the 3rd July 1983 by Hervé Gonin in the stream Ottomitan near Médouneu airport, north Gabon.
Type material collected by Peter Wagner & Ronald Windel early in on 12th December 1986 in Northern Gabon. GWW 86 / 12.
Radda & Pürzl studied these fish & placed them in Epiplatys.
The original description also contained a subgeneric name of Episemion. This was erected to full generic status with this sp. being the then sole member.
The only evidence we have is from Sonnernberg's molecular data but the problem is we don't know what the dna means. On the one had they may represent some heritable characteristoc from a common ancestor thus proving they are related. On the other hand it may represnet an adaptation made by both species independantly. PErhaps Diapteron
Abstract: Episemion krystallinoron sp. nov., the second species in this formerly monotypic genus, is
described from the Monts de Cristal in northwestern Gabon and adjacent areas in Equatorial
Guinea. It is clearly distinguished from its congener by the coloration pattern of adult males.
Species status is also supported by mitochondrial DNA data. Episemion Radda & Pürzl, 1987 is
regarded as a valid genus, distinct from all other nothobranchiid genera and probably most closely
related to Diapteron Huber & Seegers, 1977 and Kathetys Huber, 1977. It is the third described
endemic nothobranchiid species from the Monts de Cristal and adjacent areas.
The dorsolateral body color of adult males is metallic blue-green, versus metallic gold in CAT. Males have three or four rows of red dots on sides of body versus a single midlateral broad reddish-brown line in CAT.
Not the easiest fish to keep, treat as per Diapteron.
Episemion krystallinoron Sonnenberg et al. 2006 Zootaxa 1361: 6
Holotype: ZFMK 39942, male, 27.9 mm, river near vil- lage of Nkinen, crossing the road N5 from Medoneu to Kougouleu, northern part of the Monts de Cristal, Gabon, 0°58'06.3"N 10°41'33.5"E, 29 Jul 2002, T. Blum, G. Fleck & R. Sonnenberg.
Paratypes: ZFMK 39943-39945 (3), same data as holotype;
ZFMK 39948 (1), male, same data as holotype;
ZFMK 39946-39947 (2), river near Medouneu, at road
N5, northern part of the Monts de Cristal, Gabon,
1°00'06.0"N 10°45'50.9"E, 24 Aug 1999, T. Blum, F. Bitter
& P. Sewer.