Pterygiophore

The pterygiophore is the cartilage or bone on the outer end of which sit the median fin rays or spines and to which are attached erector and depressor fin muscles. There may be three cartilages that ossify into proximal, median and distal pterygiophores (or axonost, mesonost and baseost or epibaseost). The distal pterygiophore is the one next to the fin. When there are only two pterygiophores these are termed proximal and distal. In some fishes the proximal pterygiophore is very elongate and is known as a basal. Basals may be elongate enough to reach and fuse with the vertebrae, e.g. in Hippocampus. Proximal pterygiophores of the dorsal fin are also called interneurals and of the anal fin interhaemals. The last dorsal fin pterygiophore is named a stay. Vestigial pterygiophores anterior to the dorsal fin are called predorsals (or supraneurals although these are derived from neural spines). Same as fin basals.