This species was described in the genus Hypsolebias.

W. Costa (2006) 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.

Type locality:

Municipality of Guanambi: temporary pool close to road BR-030, about 1.5 km W from the confluence between the Poço do Magro River and the Carnaíba de Dentro River, São Francisco River basin, and about 3 km W of the town of Guanambi, 14°12'54" S 42°50'22" W, altitude about 505 m asl.

Discoverer(s): Wilson J.E.M. Costa et al., January 30. 2010.

Etymology: 

very, superlatively (from Latin suffix: -issimus, a, um) splendid (from Latin: splendidus, a, um), in reference to the male bright colours (according to describer, among the most colourful South American aplocheiloid killifishes).

Text-fragment from description:

A high concentration of endemic species of seasonal killifishes has been recorded for a small area encompassing the highland plateaus associated with the upper section of the Carnaúba de Dentro River drainage and adjacent drainages of the middle section of the São Francisco River basin, northeastern Brazil. The present study is primarily directed to the taxonomy of the H. fulminantis species complex in this region, and describes habitat decline and extirpation of natural killifish populations recorded in field studies between 1993 and 2017. Both morphological characters and molecular species delimitation methods using single-locus models (GMYC and bPTP) support recognition of two closely related endemic species, H. fulminantis and H. splendissimus Costa, sp. n. The new species is distinguished from other congeners of the H. fulminantis complex by having a red pectoral fin in males, well-developed filamentous rays on the tips of the dorsal and anal fins in adult males, and the second proximal radial of the dorsal fin between the neural spines of the 8th and 9th vertebrae in males.

Most recent field inventories indicated possible local extinction of populations of H. fulminantis and H. splendissimus in the studied area, but additional field studies should be made in other parts of the upper Carnaíba de Dentro River basin to evaluate the current conservation status of these species. Field studies in the Caatinga have shown that H. carlettoi is also endemic to the upper Carnaíba de Dentro River drainage, but it was never found in sympatry with H. fulminantis or H. splendissimus. Its distribution range is situated in a different subdrainage of the Upper Carnaíba de Dentro River drainage, the Mutula River subdrainage, and is separated by a distance of about 7 km from the type locality of H. splendissimus and about 15 km from the recorded geographical range of H. fulminantis

Superspecies-components:

H. adornatus, alternatus, brunoi, caeruleus, carlettoi, delucai, fasciatus, flammeus, fulminantis, gardneri, hamadryades, harmonicus, hellneri, longignatus, lopesi, magnificus, multiradiatus, ocellatus, picturatus, shibattai, splendissimus, tocantinensis, trifasciatus.

Diagnosis: separated from related fulminantis and shibattai by red pectoral fin in male (vs. hyaline in fulminantis and shibattai), well-developed filamentous rays on tips of dorsal and anal fins in adult male (vs. filamentous rays absent or rudimentary, poorly visible) (Costa, Amorin & Mattos, 2018b).

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.

Remark:

It is unfortunate that many species that were described never reached the fanciers. This is because newly discovered species are placed in alcohol shortly after their discovery and description. Since Brazilian regulations prohibit the keeping and distribution of these species within their own country and beyond, it is impossible to take photos of these species, and only photos from the original description can be taken.

I am searching for this species myself. Who has eggs of this H. splendissimus?

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

Geographical distribution of species of the Hypsolebias J’-clade in the upper Carnaíba de Dentro River drainage (yellow, H. fulminantis; red, H. splendissimus; black, H. carlettoi) and H. shibattai (white); stars indicate type localities.

Max. size 55 mm in males - female smaller.
Dorsal (average, male only )20.5,
Anal (average, male only ) 21.0,
D/A (average, male only ) 3.0,
LL scale count (average) 25.5
Pre- dorsal length to SL – 00.0 %
Depth to SL – 42.9 %
Vertebrae count (average) 35.9

Costa, Amorim & Mattos. 2018. Diversity and conservation of seasonal killifishes of the Hypsolebias fulminantis complex from a Caatinga semiarid upland plateau, São Francisco River basin, northeastern Brazil. (Cyprinodontiformes, Aplocheilidae)
Zoosyst. Evol. 94 (2) 2018, 495–504