Original described as Cynolebias flavicaudatus. Costa later assiged the species to the genus Simpsonichthys.

W. Costa (2006) then assigned many members of the genus Simpsonichthys to the subgenus Hypsolebias (Costa 2006). Hypsolebias was subsequently elevated to a genus (Costa 2011). According to some scientists, the separation of Hypsolebias from the genus Simpsonichthys is insufficiently substantiated and, therefore, debatable.

This robust-looking fish was discovered by Gilberto Campello Brasil on May 16, 1989. He found the species in the area of Lago Grande, in the province of Santa Maria de Boa Vista in northeastern Brazil. It is closely related to Hypsolebias flagellatus, which lives south of Lago Grande. H. flavicadatus is named for the yellowish color of its tail.

Superspecies components: 

H. coamazonicus, faouri, flagellatus, flavicaudatus, ghisolfii, gilbertobrasili, guanambi, heloplites, igneus, janaubensis, macaubensis, martinsi, mediopapillatus, nitens, nudiorbitatus, pterophyllus, radiseriatus, sertanejo.

Etymology: with a yellow (from Latin: flavus) tail (from Latin: cauda), in reference to the male color pattern of the Caudal fin.

Range: known only from type area in Lagoa Grande, Pernambuco state, northeastern Brasil.

Diagnosis: according to Costa & Brasil (1990), defined by 8-10 dark vertical bars on male sides (plus, male, with a broad black margin on anal, with dorsal and caudal pale blue to white dotted, and dark filaments on rear dorsal and anal ; female, distinctive, with more vertical bars and two series of black blotches on mid sides and peduncle) ; however, the initial diagnosis vanishes with the description of new cryptic species in 2003 and 2012 ; separated from the very related flagellatus by lacking black and brilliant spots on anterobasal part of male dorsal (Costa, 2003a) ; separated from related components by a variety of morphometric and pattern characters (including of female), according to Costa, Amorim & Mattos (2012).

This species can be productive, and the fry is small. Immediately after hatching, the fry should be fed with freshly hatched Artemia nauplii (brine shrimp) or better Paramecium. As most annual species do, they spawn by diving entirely into the substrate. It is best to provide a container with a lid on top in which a hole is made to allow the fish access. That container will need to have enough peat in it for the fish to dive completely into it. For most Hypsolebias species, egg development is complete after 8-10 weeks. However, it is wise also to check a few weeks earlier to see if any eggs have fully developed. Do not let the peat dry too far because the Hypsolebias like it moist. The development will be slower at storage temperatures between 21 and 24 Celsius and speed up at 25-29 Celsius. Before watering the eggs, put some eggs in the water of about 18-20 degrees Celsius to see if the eggs hatch correctly. That usually happens within 2-6

hours. Then, if eggs hatched well and fry, swim correctly, bring all remaining peat in the water. You may need to re-pack the peat after pouring over the first group of fry to a larger tank. With regular water changes and sufficient food, the young will grow quickly, and after about 5-6 weeks, they can already produce their first eggs. Since this genus has an annual life cycle, the expected life span in captivity is not much more than 10 to 12 months. Their life expectancy is limited to when their pool still has water in the wild. This period can vary from 6 to 8 months.

Remarks:

Simpsonichthys flavicaudatus is seldom seen in the hobby and need some extra attention for conservation. If you have this species please contact me so we can excange.

Look for detailed info on this species at: https://www.killi-data.org/ Membership is free!

Max. size 6.0 cm.
Dorsal 23.0,
Anal 23.8,
D/A 1.5,
LL scale count (average)29.0
Pre- dorsal length to % SL – 45.8 %
Depth to % SL – 39.7 %

Costa, W.J.E.M. & G.C. Brasil. 1990. Cescription of two new annual Fishes of the Genus Cynolebias (Cyprinodontiformes, Rivulidae) from the Sao Francisco Basin, Brazil. Ichyolog. Explor. Freshwaters, 1 (1): 18, figs. 4-5.

Costa W.J.E.M., P.F. Amorim & J.L.O. Mattos. 2012. Species delimination in annual killifishes from the Brazilian Caatinga, the Hypsolebias flavicaudatus complex (Cyprinodontiformes: Rivulidae): implications for taxonomy and conservation.

Endruweit, M. 2009. E-BR 03-07 - Eine neue Fundortvariante von Simpsonichthys flavicaudatus. D.K.G. (Deutsche Killifisch Gemeinschaft) Journal, 41 (3): 61-63, figs.

Costa, W.J.E.M. 2010e. Historical Biogeography of cynolebiasine annual Killifishes inferred from Dispersal-Vicariance Analysis. Journal of Biogeography (J. Biogeogr.), 37: 1995-2004.

Costa, W.J.E.M. & P.F. Amorim. 2011. A new annual Killifish species of the Hypsolebias flavicaudatus Complex from the São Francisco River basin, Brazilian Caatinga (Cyprinodontiformes: Rivulidae). Vertebrate Zoology, 61 (1): 99-104, figs.