Fourteen species of nonmarine gastropod opercula are found to be in high abundance in the Oligocene upper member of the Yehucheng Formation,Lanzhou Basin,northwest China.They are attributed to two families,namely Bith...Fourteen species of nonmarine gastropod opercula are found to be in high abundance in the Oligocene upper member of the Yehucheng Formation,Lanzhou Basin,northwest China.They are attributed to two families,namely Bithyniidae and Assimineidae,and four genera,namely Pseudemmericia,Bithynia,Mirolaminatus and Assiminea.Among them,three species are new,and they are Bithynia paramonolithic sp.nov.,B.obliquus sp.nov.,and B.disregularis sp.nov.Some of these species were first discovered in Paleogene strata of the vast Northwest China and can be compared with the opercula recovered from the Paleogene deposits in East and South China.It is inferred from the paleontology and sediment associations that the climate was slightly humid and the fauna probably inhabited the fresh or brackish water of a shallow lake in the Lanzhou Basin during the late early Oligocene period.展开更多
兰州盆地咸水河组下红泥岩共产有15属25种哺乳动物化石。位于下红泥岩中部的峡沟和上西沟等地产有11属20种化石（Amphechinus cf. A. rectus, A. cf. A. minimus, Amphechinus sp., Soricidae indet., Sinolagomys kansuensis, S. cf. S...兰州盆地咸水河组下红泥岩共产有15属25种哺乳动物化石。位于下红泥岩中部的峡沟和上西沟等地产有11属20种化石（Amphechinus cf. A. rectus, A. cf. A. minimus, Amphechinus sp., Soricidae indet., Sinolagomys kansuensis, S. cf. S. major, Yindirtemys grangeri, Y. xiningensis, Y. ambiguus, Eucricetodon sp., Tachyoryctoides? sp., Parasminthus asiae朿entralis, P. tangingoli, P. parvulus, Parasminthus spp., Sinosminthus sp., Heterosminthus lanzhouensis, Litodonomys huangheensis和Didymoconus berkeyi），被称为峡沟动物群。其中8属11种与党河Taben朾uluk动物群共有。两者的时代大致相当，为晚渐新世。位于瞿家川附近的下红泥岩下部产有：Desmatolagus cf. D. gobiensis, Ordolagus sp.,Tataromys plicidens, Tsaganomys altaicus, Amphechinus cf. A. minimus和Sinolagomys kansuensis等。该动物群的面貌显得比峡沟动物群的要老，而与其下的黄砂岩中所产的南坡坪动物群较相似，其时代有可能为早渐新世晚期。如果更多的化石证明是这样，那么在兰州盆地同一时代的同一动物群可产于不同的岩层（黄砂岩和下红泥岩下部），而代表不同时代的不同的动物群产于同一岩性地层中。早。展开更多
基金supported by the National Natural Science Foundation of China(Grant No.42172010)。
文摘Fourteen species of nonmarine gastropod opercula are found to be in high abundance in the Oligocene upper member of the Yehucheng Formation,Lanzhou Basin,northwest China.They are attributed to two families,namely Bithyniidae and Assimineidae,and four genera,namely Pseudemmericia,Bithynia,Mirolaminatus and Assiminea.Among them,three species are new,and they are Bithynia paramonolithic sp.nov.,B.obliquus sp.nov.,and B.disregularis sp.nov.Some of these species were first discovered in Paleogene strata of the vast Northwest China and can be compared with the opercula recovered from the Paleogene deposits in East and South China.It is inferred from the paleontology and sediment associations that the climate was slightly humid and the fauna probably inhabited the fresh or brackish water of a shallow lake in the Lanzhou Basin during the late early Oligocene period.
