The angular bones on the end of the fourth and fifth rays of the gonopodium of male livebearers. The fin can sometimes be divided into two parts, and these may appear joined. If so, the anterior part is spinous, and the posterior part is composed of soft-rays. A protuberance on the anterior portion of ray 4 of the gonopodium of some livebearers. This is generally composed of one or more segments.
F falcate Deeply concave and shaped like a sickle.
In a falcate fin the middle rays are much shorter than the surrounding rays. A membrane connecting two different parts such as the membrane joining the upper jaw to the snout. G ganoid A type of scale with a hard enamel-like outer layer that grows from underneath and from the outer surfaces of the margin. Although these may occur on other gill arches, as well, they are often rudimentary and not used taxonomically. The modified anal fin of males belonging to the family Poecillidae.