| Yucatan molly | |
|---|---|
 | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Cyprinodontiformes |
| Family: | Poeciliidae |
| Genus: | Poecilia |
| Species: | P. velifera |
| Binomial name | |
| Poecilia velifera (Regan, 1914) | |
| Synonyms [2] | |
Mollienesia veliferaRegan, 1914 | |
Poecilia velifera, known as the Yucatan molly and also as the giant sailfin molly amongst aquarists, [3] is a large livebearer that lives in coastal waters of the Yucatan Peninsula. These live-bearer (Poeciliidae) fish are particularly well known for both the extreme size variation among males, and the sexual dimorphism between males and females in both body shape and behavior.
It is outwardly similar to the sailfin molly, P. latipinna, though larger overall and with a higher and longer dorsal fin in males. Full-grown fish are usually larger than 10 cm (4 in) and large females can reach almost twice this length, though especially captive-bred individuals grow only to the size of sailfin mollies. The dorsal fins are the most distinctive character for telling the species apart: Those of the Yucatan molly have nearly 20 fin rays, counting where the fin meets the back, whereas the sailfin molly has less than 15 (intermediate numbers may indicate hybrids).
If the males spread their dorsal fins in display, these have a distinct fan or trapezoid shape, with the upper edge being distinctly longer than the lower. The height of the dorsal fin, measured at the posterior edge, is a bit larger than the height of the tail.
