薄鳞鱼类化石的新发现及其地层意义

本文记述了薄鳞鱼类(leptolepids)一新属新种——罗家峡隆德鱼(Longdeichthys luojiaxiaensis gen.et sp.nov.)。它和广泛分布于我国北方的另一原始真骨鱼类狼鳍鱼(Lycoptera)共生。因而,为研究真骨鱼类的演化和确定我国北方中生代含鱼岩系的时代及地层对比上,提供了新的资料。

A NEW LEPTOLEPID FISH FROM NORTH CHINA

The new leptolepid, Longdeichthys luojiaxiaensis (gen. et sp. nov.), was collected from Upper Jurassic of Ningxia (Ⅴ2333) and Nei Mongol (Ⅴ2334), China. It was found together with another primitive teleost Lycoptera. Diagnosis Medium-sized fish with fusiform body. Length of skull contained 4 times in standard body length. Frontals large, wide behind orbits. Paritals medium. meenting in mid-line, not separated by the supraoccipital. A single, long supraorbital. Postorbital absent. Supraorbital sensory canal ends on posterior margin of frontal. Maxilla long, arcuate, bearing 2 supramaxillae. Coronoid process of dentary prominent. Jaws thoothless. Opercular twice as deep as subopercular Preopercular with about 10 branches of sensory canal. Parasphenoid with basipterygoid process and lacking teeth. Vertebral centra ossified but slightly constricted, number of vertebrae about 45, diplospondylous present in the caudal region. Supraneural and epineural bones present. Pectoral fin with 14 rays, pelvic with 9—10, dorsal with 15—17, anal with 25—26 and caudal with 19. Origin of dorsal fin opposite to midway between anal and pelvic. Caudal fin homocercal and caudal skeleton as that in usual primitive teleosts, and with 2 urocentra, 6 hypurals, 7 uroneurals, the first uroneural extending forwards on to the second pre-ural centrum. Scals cycloid. From the characters mentioned above the fish differs from all known genera of Leptolepidae in the diplospondylous in the caudal region, the size and relative position of unpaired fins.