昆都仑鱼(Kuntulunia)在陕甘宁盆地的发现及其地层意义

本文记述了在宁夏六盘山群的李洼峡组和马东山组发现的长鳍昆都仑鱼 (Kuntulunia longipterus Liu, Ma et Liu 1982) 化石.此项研究,加深了对昆都仑鱼形态与分布的了解,并根据六盘山群鱼类化石的不同分布及其地层层序,提出六盘山群侏罗—白垩系的界线划在和尚铺组与李洼峡组之间;志丹群泾川组与和尚铺组大致相当.

DISCOVERY OF KUNTULUNIA FROM THE SHANGANNING BASIN OF NORTH CHINA AND ITS STRATIGRAPHIC SIGNIFICANCE

Kuntulunia, as one of the principal constituents of Kuyangichthys fauna, was foand from the Guyang Formatian (Early stage of Early Cretaceous) of the Guyang Basin, Nei Mongol in 1976-1977. It is the first time that Kuntulunia longipterus was discovered in the Liwaxia and the Madungshan Formations of the Liupanshan Group, Ningxia province in 1981. Because the Liwaxia Formation overlies the Lycoptera-bearing Heshangpu Formation, we suggest that a Jura-Crataceous boundary line of the Liupanshan Group should be drawn between the Heshangpu and the Liwaxia Formations. The Lycoptera-bearing Jingchuan Formation of the Zhidan Group corresponds to the Heshangpu Formation. The specimens are better than that of Nei Mongol. According to our observation of the specimens of Nei Mongol and Ningxia, we put forward some amendments and addi- tional remarks to the characters of the genus. The frontaIs are short and broad. The parietals ate large and not separated by the supraoccipital. Supraorbital canals are ended in the posterior margin of the frontals. The temporal fenestra is roofed by the bone plates of the skull roof. A low coronoid process is only present on the posterior part of the dentary. The supramaxilla is absent. Both the premaxilla und the deutary are toothed and the teeth are not restrieted in the frot part of the deutary. The maxillae are toothless. The premaxilla forms the upper mouth border and the maxilla is nearly excluded from the mouth gape. The parasphenoid is toothless. There is the supraorbital. The third infraorbital is largen. The origin of the pelvic fin is in the midway between the pectorals and the anal. The number of hypurals is not six but seven. There are three to four uroneurals and three of them extend forward beyond U2. There is a complete neural spine in PU1. The number of branched fin rays of the caudal fin is 16. Scales are cycloid and the nucleIus is near the posterior part.