西藏南部下鲁硅岩晚侏罗世罩笼虫(放射虫)新材料

下鲁硅岩为藏南日喀则地区雅鲁藏布蛇绿岩南侧的晚侏罗世—早白垩世硅质岩系。本文补充描述了该岩系中 4块标本的罩笼虫亚目放射虫化石 1 6属 2 3种 ,包括 8个新种。加上这些标本原已描述过的 1 8属 3 3种 ,共有 3 4属 56种。所有的属和近一半的种见于北美西部 ,可与那里的晚侏罗世放射虫分带很好地对比 ,它们分别相当于那里牛津期的 2 γ亚带和晚启莫里期—早提索期的 3 β亚带。动物群具特提斯生物地理区特征 ,但与西特提斯的地中海地区同期动物群显然不同 ,可能当时东特提斯与太平洋联系密切。

New data of the Late Jurassic nassellarian (radiolaria) from the Xialu chert in southern Tibet

Xialu chert is named for a Late Jurassic to Early Cretaceous siliceous sequence on the southern side of the Yarlung Zangbo ophiolite belt in Xigaze area,southern Tibet.There are 23 species,including 8 new species,to be described here from 4 samples of the Xialu chert.Plus the previous described species,total 34 genera and 56 species have been obtained from these samples.Of them all of the genus and about a half of the species have been found in the Jurassic strata of the western North America.The radiolarian assemblage of the sample 218 and the another one derived from samples 191,197 and 221 can be correlated with the subzones 3 beta and 2 gamma of the Upper Jurassic radiolarian zonation of the western North America respectively.On the other hand,the Xialu fauna is quite different from the contemporaneous radiolarian fauna in the Mediterranean region.Possibly,during Late Jurassic the Xigaze sea in the eastern Tethys was located in different areas with the west Tethys paleobiogeographically,but had a close relationship with the Pacific.The new species are Lupherium longicornis n.sp., Ristola macrocephala n.sp., Hiscocapsa planata n.sp., Milax conicus n.sp., Milax nobilis n.sp., Milax xizangensis n.sp., Minocapsa truncata n.sp., Protunuma (?) haoi n.sp..Of the eight new species described here three species,including Lupberium longicornis,Milax nobilis and Minocapsa truncata, are out of the sample 218,the others come from a middle Oxford radiolarian assemblage derived from the other samples.