Leptopanchax was erected in 2016 by Costa when it was discovered "Leptolebias marmoratus is more closely related to species of the genera Campellolebias and Cynopoecilus than to other species of Leptolebias, and that Mucurilebias leitao is the sister group of a clade comprising all other cynopoecilines. Leptopanchax, new genus..."
Costa noted in 2018 "Leptopanchax splendens (Myers 1942), a miniature species reaching about 20 mm standard
length (LS; Costa & Lacerda, 1988), was first described as Cynopoecilus sandrii by Faria &
Müller (1937), but this paper was not cited in the scientific literature before Costa & Lacerda
(1988)"
Properly sandrii Faria & Müller (1937) is the correct name and I regard splendens properly a junior synonym. The ICZN does not make many mistakes but unfortunately this was one of them and they are best ignored here as in other badly handled controversial cases (Adamans, Roloffia)
