trunkfish, any member of a family of fishes, also called boxfishes, that have short triangular bodies covered by firmly united hexagonal bony plates. Only the jaw, the bases of the fins, and the tail protrude from this carapace, and the locomotion of these fishes is necessarily peculiar. The dorsal and anal fins propel the fish with a rotary motion, while the tail acts as a rudder. The ventral fins move continually, forcing air through the constricted gill openings. Many trunkfishes are patterned in bright colors. They are sluggish, frequenting shallow water and feeding on minute plant and animal matter. Members of some species have been found to secrete a poison, fatal to other fishes, when disturbed. Trunkfishes are most abundant in tropical waters. The cowfish, one of the larger trunkfish species, is up to 1 ft (30 cm) long and has a short spine over each eye. Trunkfish have palatable flesh and are served baked in their shells by the inhabitants of some South Pacific islands. They are classified in the phylum Chordata, subphylum Vertebrata, class Osteichthyes, order Tetraodontiformes, family Ostraciidae.