 Species in this genus resemble egg-laying Cyprinodontoidei such as Fundulidae (topminnows) at first glance, and are thus sometimes called "killifish" though this is technically erroneous.FishBase currently recognize 3 species in this genus, but based on genetics, external characters, morphometrics and meristics "H. formosa" (the type species of the genus) is not closely related to the remaining, which have been moved to their own genus, "Pseudoxiphophorus".There are probably more remaining undiscovered as these fishes are rather inconspicuous.