The family of Threefin Blennies (Tripterygiidae) or also known as tripterigids, is a group of species belonging to the order Perciformes, in which we find exclusively marine and mainly tropical species. Its scientific name derives from the Greek word 'tripteros', which means 'with three wings' since, as we will see later, its dorsal fin is divided into three regions. Their distribution is very wide, and they can be found in clear, shallow waters of the Atlantic, Indian and Pacific Oceans. They are extremely diverse in the Indo-Pacific, while in the Atlantic there are relatively fewer species. They are benthic species, which usually live on the sea bed, either rocks or coral.
The body of the Threefin Blennies is elongated and very similar to that of the Combtooth Blennies. The species that reaches the longest length is Notoclinus fenestratus, measuring up to 20 cm in length, although in general most species barely reach 6 cm in length. The body is usually very colored, which allows them to camouflage with the environment. The vast majority of species present sexual dichromatism, that is to say, the coloration of the females and the males is different. Generally the females are duller in colour, while the males are more colourful. There are two characteristics which differentiate the Threefin Blennies from the Combtooth Blennies. The first, as its name indicates, is that the Threefin Blennies have a dorsal fin divided into three regions, while the dorsal fin of the Combtooth Blennies is usually unique and continuous. The second distinctive feature of the Threefin Blennies is the absence of cirrus, a thin structure that protrudes from the body and is associated with the eye region.
As previously mentioned, the characteristic dorsal fin of the Threefin Blennies is divided into three regions. The first two regions are composed entirely of spines and the third region is composed of more than 7 soft radii, but never a number greater than that of the spines of the first two dorsal fins. The pectoral fins are elongated and extend in a fan shape. The pelvic fins are small and have 1 spine. The anal fins are long and either lack spines or have a maximum of 2.
The Threefin Blennies are diurnal and very territorial species. Their diet is based primarily on small benthic invertebrates. There are 171 species described in the tripterigids family, which are organized to form a total of 29 different genera.