Butterfly splitfins

An adult pair of butterfly splitfins (Ameca splendens)...

And a week old fry

They are born large.

Why are they called split fins.

Uberhoust said:

Why are they called split fins.

Click to expand...

The name splitfin is derived from the fact that male splitfins have an andropodium instead of a gonopodium (male ovoviviparous livebearer males) as a sexual organ. An anal fin of a male splitfin's has got a small notch on the front of the anal fin close to the body which we call an andropodium. But this notch on the anal fin looks as if the anal fin is split. That's why thy goodeids are called splitfins.

Thanks for the clear explanation.