ABSTRACT
The dealfishes or ribbonfishes (Trachipteridae) are moderately sized, mesopelagic lampridiformes that are distributed in all oceans including northern seas. The family contains three genera (Trachipterus, Zu and Desmodema) and about 9-10 species (Olney 1984, Nelson 1994). Trachipterids are elongate and laterally compressed, often with conspicuous and large black pigment spots scattered laterally on shiny silver bodies. The dorsal-fin is crimson or red in life and has elongate anterior rays. As with all lampridiform fishes, the jaws are very protrusible. The anal fin is absent. The pelvic fin is rudimentary in adults of some species, although conspicuous in young fish. The skin of adults bears tubercles. In life, trachipterids probably assume a head-up swimming posture and move through the water with undulations of their long dorsal fins. Prejuveniles have been observed swimming in surface waters with their long anterior dorsal-and pelvic-fin rays trailing behind like the tentacles of jellyfish (Heemstra & Kannemeyer 1977). Trachipterids are hypothesized to be the sister group of the oarfishes (Regalecidae). These families share the lack of an anal fin and the presence of spinules (tiny laterally projecting spines) on caudal-and pelvic-fin rays. Together, the trachipterids and the regalecids are the sister group to the radiicephalids and lophotids. These four lampridiform families are united by the common possession of lateral spinules on dorsalfin rays, vomerine teeth and greater than 60 vertebrae (Olney et al. 1993, Wiley et al. (1998). Currently there is no hypothesis of trachipterid intrarelationships.
