Rivulins of the Old World Chapter 7 The Ctenoidy of Males
"The spines of scales and fin rays are often covered by tissues which extend far beyond the end of the spine, producing slender soft filaments or "sensory-papillae". This character is well developed in Fundulopanchax and Nothobranchius and GUI and OCC. Whereas in Aphyosemion (Fundulopanchax) the ctenoid scales are usually found anteriorly and low on the sides and very rarely on the head. In all cyprinodons the ctenoid spines generally are situated at a right angle to the surface of the scale."