Surgeonfish, also called tang, any of about 75 species of thin, deep-bodied, tropical marine fishes of the family Acanthuridae (order Perciformes). Surgeonfishes are small-scaled, with a single dorsal fin and one or more distinctive, sharp spines that are located on either side of the tail base and can produce deep cuts. The spines, which resemble a surgeon?s scalpel, may be either fixed in place or hinged at the rear so they can be opened outward and directed forward. _____________________________________________________________________________________________ taken while diving in the Maldives.