日本産アナゴ科魚類の研究 III. : ミナミアナゴ属 Japonoconger new genus とその近縁属

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The genera Rhynchocymba and Rhynchoconger were both erected by Jordan and Hubbs ('25), in their taxonomic study on the Japanese congrid eels. Parr ('32) questioned the validity of those genera, and provisionally placed them in synonymes of the older genus Ariosoma. In their revisional study on the Japanese species, Matsubara and ochiai ('51) agreed to this opinion, and they referred two subspecies and two species to it, viz., Ariosoma nystromi nystromi, A. nystromi xenica, A. ectenura and A. sivicola, the first one of which was reduced to subspecific rank of Rhynchocymba nystromi, and the second and the last were newly established by them. On the other hand, Wade ('46), discussing several characters of the three genera desclibed above, recognized Rhynchocymba as a distinct genus. His investigation, however, indicated that the genus Rhynchoconger should be considered as a synonym of the genus Rhynchocymba. This conception was accepted by Matsubara ('55). In the present paper, the author has re-examined the Japanese species referred to the above-mentioned genera in order to clarify the status of those genera. Upon carefully investigations of the origin of dorsal fin, dentition on upper jaw, vomer and upper pharyngeal bone, sensory pores on head, lateral line scales, labial flange, preorbital bone and vertebrane, the author has come to the following conclusion: 1. The genus Rhychocymba Jordan and Hubbs comprises 3 formes, R. nystromi nystromi (Jordan and Hubbs), R. nystromi ginanago Asano and R. nystromi xenica (Matsubara and Ochiai), so far as the Japanese species are concerned. 2. The genus Rhynchoconger Jordan and Hubbs in here again accepted as a valid one for the type species Rhynchoconger ectenura (Jordan and Richardson). 3. A new genus Japonoconger is proposed here, with J. sivicola(Matsubara and Ochiai) as genotype. Japonoconger new genus Genotype: Arisoma sivicola Matsubara and Ochiai Description: Upper jaw well projected in front of tip of lower jaw when mouth is clossed. Eye rather small, about half length of snout in diameter. A longitudinal fleshy keel runs along the midline on lower surface of tip of snout. Upper lip without upturned free flange. Inferior edge of labial canal with 2 or 3 bony projections. Cephalic sensory pores moderate in number; 5 on supraorbital canal 5 on infraorbital canal, 7 on mandibular canal, 3 on preopercular canal and 1 on supratemporal commissure at the top of head. Tail usually more than twice as long as the lest of the body. Teeth mostly small, conical in shape, but especially blunt on vomer. Bands of teeth on premaxillary, maxillary and vomer separated each other by an interspace. Premaxillary teeth slightly exposed on lower surface of tip of snout when mouth is closed. Upper pharyngeal consists of two bony plates, the anterior one of which is a little smaller than the posterior one. Structure of lateral line scales referable to Uroconger-type. Abdominal vertebrae about 50 fewer than caudal one. Air bladder normal in shape, but the anterior tip begins far backward from posterior end of stomach. Consequently, pneumatic duct remarkably elongated. Remarks: The present new genus resembles Rhynchocymba and Rhynchoconger, but those features given in the following key may enable us to distinguish it from the other two genera: 1a. Dorsal fin begins vertically a little behind base of pectoral. Dentition of upper jaw and vomer connected with each other. Upper pharyngeal bone made of a single bony plate. Lateral line scale referable to Conger-type. 2a. Patch of teeth on premaxillary much smaller than that on vomer (Fig. 1, A-C). Cephalic pores moderate in number, about 24 in total on one side of head including 1 placed on top of occipital region. Abdominal vertebrac about 40 fewer than caudal ones......Rhynchocymba 2b. Patch of teeth on premaxillary more or less larger than that on vomer (Fig. 1, D). Cephalic pores rather fewer than those of Rhynchocymba, about 18 in total on one side of head in
社団法人日本動物学会の論文
1958-10-15

日本産アナゴ科魚類の研究 III. : ミナミアナゴ属 Japonoconger new genus とその近縁属

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