1) F. gardneri gardneri has spots on the anal fin.

2) F. gardneri nigerianus has the same stripes as the other unpaired fins.

there's also gardneri mamfense from cameroon, and garneri lacustre from the nigeria/cameroon border. mamfense are rare in the hobby, lacustre even more so.

F. gardneri claseni has few spots and is usually the one that shows up in books usually mislabeled in older books as calliurum (blue fin margins) or calliurum ahli (yellow fin margins). Calliurum and ahli are australe like fishes and although this mess had been sorted out by 1960 books took a while to catch on; one is still wrong.

Nigerianus isn't common in books although it shows up in older European books sometimes with a photo of filamentosum instead. Prior to the 1970s all bets are off as far as accuracy in names goes in older literature.

Of all the books that have killifish pictures only Scheels book, before 1970 got the names all right. It was confusing at first but now we understand that gardneri is a super species found all over Nigeria and further out but that it occurs in five major variants based on geography. There are many many populations within each subspecies and even these show great variation.

The yellow and blue finned variants proved to be not only the same species but found in the same stream together. We isolate blue and yellow finned forms but nature does not.