本科はDerichthys, Nessorhamphusの2属からなり、各属はそれぞれ1種を含む。Derichthysの吻は丸い。また吻の形状が本種に似るクズアナゴ科(Nettastomatidae)魚類では、両顎がほぼ同長であり、後鼻孔が眼の近辺か、その後方に開く(Beebe, 1935a; 1935b; Robins and Robins, 1971)。(上野・佐々木)
Distinctive characters:
Snout long, depressed, and spatulate in form. Upper jaw produced far beyond tip of lower jaw. Anus distinctly behind middle of body, total length 1.6 times of preanal length. Lateral line distinct. Anterior and posterior nostrils opened near tip of snout. Pectoral fin long, subequal to snout. Dorsal fin originated over tip of pectoral fin. Dorsal and anal fin rays rather abruptly become shorter near tip of tail and once again become longer, so that it appears an independent caudal fin present. Teeth conical and make broad bands on jaws.
Distribution:
Warm seas of the world.
Remarks:
The present family is comprised of 2 genera, and each genus represented by single species. Derichthys has roundish snout. Duckbill eels (Nettastomatidae) are similar to the present species in having long snout, but their upper and lower jaws subequal in length, and posterior nostril opened near eye (Beebe, 1935a; 1935b; Robins and Robins, 1971). (Uyeno and Sasaki)