Wikipedia
Veliferidae
Sailfin moonfishes are a small family, Veliferidae, of lampriform fishes found in the Indian and western Pacific Oceans. Unlike other lampriforms, they live in shallow, coastal waters, of less than depth, rather than in the deep ocean. They are also much smaller than most of their relatives, up to in length, and have deep, rather than elongated, bodies. They are characterised by their ability to retract the anterior rays of their dorsal and anal fins into a sheath.