gon·o·po·di·um 
(gŏn′ə-pōdē-əm)
(gŏn′ə-pōdē-əm)n. pl. gon·o·po·di·a (-pōdē-ə)
The modified anal fin of the male of certain fishes, such as guppies, used to transfer sperm into the female.
[New Latin : GONO- + Greek pous, pod-, foot; see PODIUM.]