This species was initially described in the genus Simpsonichthys.

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.

Discoverer(s): Wilson J.E.M. Costa et al., January 31. 2010.

Type locality: near road BR-030, about 8 km northeast of Malhada village, rio São Francisco floodplains, Malhada municipality, Bahia state, altitude about 440 m , (eastern) Brasil.

Etymology: in honor of Scottish naturalist George Gardner (1810-1849), present in Caatinga type area during his trip to Brasil between 1836 and 1841, making rich natural history collections (including plants and fossils).

Diagnosis: separated from other components of magnificus superspecies except picturatus by minor details in male color pattern and from picturatus by minor morphomeristics

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.

From the paper:

A great diversity of animal species adapted to life in the semi-arid Caatinga of northeastern Brazil, including seasonal killifishes, has been reported in the last three decades. More recently, field and molecular data have shown a high occurrence of cryptic species. The killifish group herein analysed, the "magificus species group", is endemic to the middle and southern portion of the Caatinga, occupying about 120 km along the floodplains of the middle São Francisco River and some adjacent tributaries. Species of this complex are rare and presently considered threatened with extinction, being uniquely found in pools protected by trees and bushes. Single-locus delimitation methods were used to test species limits of populations displaying different colour patterns along the whole distribution of the complex. All analyses consistently supported the three nominal species and two new,  

herein described: H. gardneri Costa, sp. n., from the floodplains of the middle São Francisco River and H. hamadryades Costa, sp. n., from the Gorotuba River floodplains. The phylogenetic analysis highly supports H. hamadryades as sister to a clade comprising H. gardneri and H. harmonicus. Our field observations suggest that H. hamadryades is a miniature species. This study indicates that the H. magnificus complex comprises cryptic species apparently endemic to small areas and extremely vulnerable to environmental changes, deserving high concern. Simpsonichthys Costa, 2006 is the most species rich and morphologically diverse seasonal killifish genus in the Caatinga, where it is represented by two clades highly supported by morphological and molecular data (Costa 2006; Costa et al. 2017), the H. antenori group (Costa 2007; Costa et al. 2014, 2018) and the H. magnificus group (Costa 2007). Among species of this clade is H. magnificus (Costa & Brasil, 1991) and two closely related species, H. picturatus (Costa, 2000) and H. harmonicus (Costa, 2010) (Costa 2007, 2010), which together form a species complex, herein called the H. magnificus complex (hereafter HMC), distinguished from all other congeners by the presence of a narrow black margin on unpaired fins and pectoral fin in males (vs. black margin absent) and unpaired fins rounded or slightly pointed (vs. sharply pointed) (Costa 2010). Like other closely related congeners, HMC species live only in shadowed parts of the pools, protected by dense concentration of shrubs and trees (pers. obs. 1994–2018).

Species of this genus 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 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:

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Max. size 50 mm in males - female smaller.
Dorsal (average, male only ) 23.0,
Anal (average, male only ) 21.5,
D/A (average, male only ) -1.5,
LL scale count (average) 25.5
Pre- dorsal length to SL – 44.6 %
Depth to SL – 37.5 %
Vertebrae count (average) 26.5

Costa W.J.E.M., P.F. Amorim, J.L.O. Mattos, 2018. Cryptic species diversity in the Hypsolebias magnificus complex, a clade of endangered seasonal killifishes from the São Francisco River basin, Brazilian Caatinga (Cyprinodontiformes, Aplocheilidae). Zookeys, 777: 141-158, figs.