They are usually smallish; most species reaching a length of at most 4 in (10 cm) when fully grown. However, a few larger species exist, with the giant killifish (F. grandissimus) and the northern studfish (F. catenatus) growing to twice the genus' average size.
Many of the 40-odd species are commonly known by the highly ambiguous name "killifish" (the general term for egg-laying toothcarps), or the somewhat less ambiguous "topminnow" (a catch-all term for Fundulidae). "Studfish" is a quite unequivocal vernacular name applied to some other Fundulus species; it is not usually used to refer to the genus as a whole, however.
Species
Russetfin Topminnow (F. escambiae)
There are currently 39 recognized species in this genus:[1]
Formerly placed in Fundulus were the closely related diamond killifish (Adinia xenica) and the somewhat more distantly related Cuban killifish (Cubanichthys cubensis, a pupfish).
