骨舌鱼科化石在我国的发现

本文记述了在四川芦山县发现的骨舌鱼科—新属、种——芦山中华骨舌鱼 (Sinoglossus lushanensis, gen. et sp. nov.).在对其形态特征作较详细描述的基础上,认为它与 Osteoglossum、Scleropages 两属较接近;同时还对骨舌鱼类的起源地、中华骨舌鱼的地质时代及其生存环境等问题作了探讨.

THE DISCOVERY OF A FOSSIL OSTEOGLOSSID FISH IN CHINA

A new osteoglossid genus and species, Sinoglossus lushanensis, from Lushan Xian, North Sichuan, is described. It attains a total length of about 80 to 220 mm, having elegantly fusiform body. The maximum depth of the body, which is aboug 1/3.5 in the total length, is smaller than the length of the head including opercular apparatus, Measurements of the holotype are give in the text. The characters of the skull-bones, all the fins and scales reserdble those of living osteoglvssids. The head is large and almost trianglar in lateral view. External skullbones are much thicekened and covered with enamel. The skull roof is unsatisfactory]y preserved, but the nasal and frontal can be ascertained, the former appear to be fairly large, the latter is very large. The cheek region covered by third and fourth infraorbitals which very enlarged and expanded to the preopereular. The oral border of the upper jaw formed by long maxilla and small premaxilla, providing with a number of conical teeth, but those on the maxilla appear to be relatively long and slightly curved. The mandibular is long, narrow and slightly deepening posteriorly. The anterior part of the dentary pvoides conical teeth. The operculum is very large and almost oval in otline,it is about one and a half times as deep as wide. The suboperculum and interoperculum are rusdimentary, the former is very small, the latter is net visible in lateral view. The preoperculum is well developed, its vettical and horizontsl limbs is joined each other nearly at right angle. The entopterygoid and basihyal bear nuraerous conical teeth. The pectoral fin consists of about 11 rays, the first is stout and unbranched. The Pelvic fin is small and contains only 7 or 8 rays. The dorsal and anal fins are directly opposed, the former is long and contains 26 to 27 rays, the latter with convex ventral margin, including 17 to 20 rays. The caudal fin is small, with convex hind border, in cluding about 10 branched rays. The body is covere rd with large cycloidal scales, displaying charaeteristc reticulate strracture. As deseribed above, Sinoglossus conforms with charaeters of Osteoglossidae, and is closest to Osteoglossum and Scleropages in the body form, the skull-bones, the opercular apparatus, the caudal fin, and scales etc. but it differs distinctly from Osteoglossum, Scleropages and other genera of the family in following combination of characters: Bady Small. Mouth gape moderately deep, not oblique. Mandibular artieular Placed below the posteror edge of the orbit. Mandibular not prominent. Antorbital, with which first infraorfbital appear to be fused, very large and ornamented with ridges. Seeoad infraorbital rather large. Anal fin with fewer fin rays. Dorsal fin shorter than that in Osteoglossum, but longer than that in Scleropages. Ventral fins nearly equally distant from end of snout and caudal fin. Caudal fin with about 10 branehed rays. The living osceoglossids are freshwater fishes of the tropicul regions of South America, Africa, Southeast Asia, and Australia. Sinoglossus represents the first discovery of the Osteoglossidae in China. This new discovery is of great interest in studying of the Paleoclimate and the place of origin of the osteoglossoids. Nelson (1969) raised hypothesis of osteoglossomorph orilgins in Gondwana based on the distribution of living osteoglossods in southerclontinent. However, a primary freshwater teleost, Lyooptera kmown from late Jurassic in Ohina and early Cretaceous in Mongolia and Siberia, has been cansidered as a representative of the family Hidontidae (Greenwood 1970). Patterson (1975) Pointed ont that the occurrence of hiodoatids in N. E. Asia as early as the lowermost Cretaceous raises severe difficulties for Nelson's hypothesis of osteoglossomorph origins in Gondwana. Zhang and Zhou (1976) considered that two interesting forms of Lyopteridae, Lycoptera [Asiatolepis] sinensis and Paralycoptera wui found from late Mosozoic freshwater deposits in E. China, should be early members of the Osteoglossoidei, beeause they bear charaeters closely resembling Osteoglossoidei Therefore they proposed the hypothesis of osteoglossomorph origin in E. Asia. The discovery of Sinoglossus from Tertiary period of Sichuan has further indicated that the osteoglossomorPhs had probably its origin in East Asia. Sinoglossus luskanensis occurs in the freshwater deposits of Sichuan Basin, but its exact horizon is not clear. Judging from the matrix rock in which the fossil fishes embedded, it probably belongs to the Lushan Formation, and can be regarded as Eocene. The fish-bearing depcsits probably represent the late middle or stage of the peviod and indieate a waimer climate.