Apagesoma-edentatum , A New Genus And Species Of Ophidiid Fish From The Western North-Atlantic

A new genus and species of deep-sea fish, Apagesoma eden/alum, (family Ophidiidae), is described from deep waters off the Bahamas. It can be distinguished from other ophidiid genera by the following characters: an enlarged and swollen anterior nostril; eyes placed anteriorly on the head; moderate-sized, unsculptured, hemispheric-shaped sagitta; absence ofa basibranchial tooth patch; absence of an opercular spine; large sub-terminal mouth, with non-protrusible jaws. Typhlonus delosommalus Hureau et aI., 1979 is placed in Apagesoma based on similarities in otoliths, non-protrusibility of jaws, swollen anterior nostrils and absence of a basi branchial tooth patch. Typhlonus contains only the type species, T. naslls Gunther, 1878, which differs from Apagesoma in possessing a much larger and highly sculptured otolith, highly protrusible jaws and presence of a basibranchial tooth patch. A single specimen 1 of ophidiid fish captured from the western Atlantic off the Bahamas in 5,082-m depth proves to be a new genus and species which is here described as Apagesoma edentatum. A second species is referred to Apagesoma from Typhlonus. Seven specimens of T. nasus, all colleeted in the same region of the Indo-Pacific, provided the basis for a detailed study and redescription of the genus by Nielsen (1965). Two additional specimens of T. nasus were recently collected from the southern part of the Arabian basin and the southeastern Pacific Ocean at abyssal depths (Shcherbachev and Tsinovsky, 1980) and two specimens from the region between the equator and Hawaii in the Pacific Ocean (Cohen, pers. comm.). More than 100 years elapsed after the original generic description before a second species of the genus, T. delosommatus, was described from the western Atlantic (Hureau et aI., 1979). The differences between T. nasus and T. delosommatus were so pronounced that the authors considered establishing a new genus for the latter. METHODS AND TERMINOLOGY Counts and measurements follow those of Hubbs and Lagler (1958) except that the upper jaw symphysis is used as the anteriormost point instead of the tip of the snout. Head length is measured to the posterior tip of the bony operculum. Measurements are presented as percent of standard length (SL). Vertebral and fin ray counts were determined from radiographs. Caudal fin rays are only those rays attached to the hypurals. Shape and size of the dentary, premaxillary, palatine and pharyngeal tooth patches were determined from clay impressions. Measurements were made with dial calipers to the nearest 0.1 mm; measurements less than 5.0 mm were made with the aid of an ocular micrometer. The sagitta was removed from the preserved holotype and described following the terminology of Frizzel and Dante (1965). All illustrations except Figure I were drawn with the aid of a camera lucida.