OSTEOLOGY AND RELATIONSHIPS OF PSEUDOTRICHONOTUS-ALTIVELIS (TELEOSTEI, AULOPIFORMES, PSEUDOTRICHONOTIDAE)

The osteology of the rare Japanese fish Pseudotrichonotus altivelis is described based on several specimens collected off the Izu Peninsula. Relationships of Pseudotrichonotus are discussed based on osteologica l comparisons with other neoteleosts. The placement of Pseudotrichonot us among iniomous fishes has been questioned because of its lower numb ers of caudal-fin, pelvic-fin, and branchiostegal rays. Our investigat ion supports an iniomous affinity for Pseudotrichonotus, specifically as a member of the Aulopiformes. Within that group, Pseudotrichonotus belongs in a new suborder diagnosed herein, the Synodontoidei, which a lso includes the Aulopidae (Aulopus), Synodontidae (Synodus and Trachi nocephalus), and Harpadontidae (Harpadon and Saurida). A synodontoid a ffinity for Aulopus has never been suggested, but numerous osteologica l features support the monophyly of this clade. Synodontoids have a pe culiar proximal segmentation of most principal caudal-fin rays, expand ed neural and haemal spines on posterior vertebrae, cartilage extendin g along the ventral margin of the anterior ceratohyal, ventral displac ement of the first one to three epineurals, supraneurals with large la minar expansions and six or more branchiostegals on the posterior cera tohyal. They lack median caudal cartilages. Among synodontoids, Pseudo trichonotus is the sister group of the Synodontidae plus Harpadontidae , with which it shares paired peritoneal pigment spots, an abrupt tran sition between the epipleurals in and beneath the horizontal septum, a nd absence of the fourth pharyngobranchial toothplate. Our study does not support a previously proposed relationship between Bathysaurus and synodontids.