Any species of spiny-rayed fishes in the family Fistulariidae. Cornetfishes are elongated, depressed-bodied fishes with a greatly extended tubular snout, a very small mouth, and a long thin filament extending from the middle of the caudal fin. They are closely related to the trumpetfishes (Aulostomidae) which are more robust and lack the caudal filament. At present there are approximately five known species of cornetfishes.