Here,we describe a new primitive Erinaceidae species,Oligoechinus lanzhouensis n.gen.n.sp.,based on a specimen from late Oligocene strata of the Lanzhou Basin,Gansu Province.Its characteristics are as follows:the M1 w...Here,we describe a new primitive Erinaceidae species,Oligoechinus lanzhouensis n.gen.n.sp.,based on a specimen from late Oligocene strata of the Lanzhou Basin,Gansu Province.Its characteristics are as follows:the M1 width is longer than the length,the metastyle extends far disto-labially,the posterior margin has strong curve and a distinct metaconule that is connected to the protocone by a postprotocrista is located in the centre of the tooth.The posterior arm of the metaconule is poorly developed.In the P4,the pterion of the metastyle is less developed and the metacone is carinate.In addition,O.lanzhouensis has a premolar larger than the canine tooth(P2>C)and P3 had no molarisation,characters also possessed by Erinaceus.Overall,O.lanzhouensis was similar to Mioechinus based on architectural tooth features,demonstrating a closed genetic relationship.Fossil Erinaceidae are relatively rare before the Miocene.The discovery of O.lanzhouensis provides an important insight into the origin of Mioechinus in China and the early evolution of the Erinaceidae.Our analysis shows that a relatively recent ancestor of Mioechinus had probably existed in the early Oligocene and that O.Lanzhouensis was likely an ancestral type of Mioechinus gobiensis,and its systematic position should be located at a transitional position between Amphechinus and Mioechinus.展开更多
The Quantougou(QTG) Fauna in central Lanzhou Basin is an important late Mid-Miocene fauna on the northeastern Tibetan Plateau margin,but its numerical age remains a matter of debate.Here,we present a new magnetostrati...The Quantougou(QTG) Fauna in central Lanzhou Basin is an important late Mid-Miocene fauna on the northeastern Tibetan Plateau margin,but its numerical age remains a matter of debate.Here,we present a new magnetostratigraphic record for a fluvio-lacustrine section to further constrain the age of the QTG Fauna.Results suggest that the studied section spans from polarity chrons C5Cn.2n to C5 n.2n or C5 An.1n,with ages of ca.16.5 Ma to 10 Ma or 16.5 Ma to 12 Ma.The QTG Fauna is located at the top of polarity chron C5r.3 r or C5 Ar.2 r,which corresponds to an age of 11.7 Ma or 12.8 Ma for the fauna.Accordingly,the associated Myocricetodontinae(a subfamily of Gerbillidae,Rodentia) is suggested to have appeared in the Lanzhou Basin at 11.7 Ma or 12.8 Ma,which is the oldest Myocricetodontinae in East Asia but is still much younger than the ~20 Ma appearance of this subfamily in West and South Asia.Our age data support the interpretation that East Asian Myocricetodontinae originated from South Asia.The QTG fauna further suggest a dry and open grassland environment,which is consistent with global cooling after the Mid-Miocene Climatic Optimum.展开更多
The Asian monsoon-arid environment system began to develop during the Oligocene, but the exact position of the arid zone boundary is uncertain in the Oligocene. Fossil mammal assemblages can be used to assess the envi...The Asian monsoon-arid environment system began to develop during the Oligocene, but the exact position of the arid zone boundary is uncertain in the Oligocene. Fossil mammal assemblages can be used to assess the environment of an area. There were two sizes of mammals in the Nanpoping fauna from the Oligocene strata of the Lanzhou Basin： the small ones were grassland rodents such as Ctenodactylidae; the large ones were forest dwellers such as Paraceratherium and Paraentelodon. Of the 23 species of mammals identified in the Nanpoping fauna, -40% were forest dwellers and the rest （-60%） were grassland taxa. The Nanpoping fauna was compared with the contemporaneous Dingdanggou fauna in the Danghe area to the north and Jiaozigou fauna in the Linxia area to the south. The Nanpoping fauna contains elements of both other faunas and thus represents a transitional assemblage between forest and grassland. So, it can be inferred that the southern boundary of the arid zone in China during the Oligocene was probably near the Lanzhou Basin.展开更多
The Tertiary deposits of the Yongdeng section, the Lanzhou Basin were studied by means of magnetostrati-graphy. The magnetostratigraphic sequences from Paleocene to Miocene were established, and the time scale for the...The Tertiary deposits of the Yongdeng section, the Lanzhou Basin were studied by means of magnetostrati-graphy. The magnetostratigraphic sequences from Paleocene to Miocene were established, and the time scale for the corresponding stratigraphy and mammalian faunas was also established by referring to their correlation to the GPTS of BKSA95 (The geomagnetic polarity time scale which was thoroughly revised and updated by Berggreen et al. in 1995). In the end the paleoenvironmental records and their relationship with the uplifting of the Tibetan Plateau were discussed. The results are as follows. The top boundary of the Xiliugou Formation is dated to be 51 Ma, i.e. Eocene. TheYehucheng Formation covers the time span of 51-31.5 Ma, i.e. from late Early Eocene to early Early Oligocene. The Xianshuihe Formation covers the time span of 31.5-15 Ma, i.e. from Early Oligocene to Middle Miocene. The lower member of the Xianshuihe Formation spans from 31.5 to 20.0 Ma, i.e. from Early Oligocene to early Early展开更多
An angiosperm compression flora is found in Palaeogene from Lanzhou Basin and the cuticular analysis of Populus davidiana Dode in the flora is carefully made. Fur-thermore, the fossil cuticles are compared with the ep...An angiosperm compression flora is found in Palaeogene from Lanzhou Basin and the cuticular analysis of Populus davidiana Dode in the flora is carefully made. Fur-thermore, the fossil cuticles are compared with the epidermal structures of extant Populus leaves growing in different en-vironments, i.e. moist, semimoist, and semiarid to arid cli-matic regions. The present experiments indicate that mature leaves of P. davidiana show leaf size from big to small, leaf cuticles from thick to thin and anticlinal walls of epidermal cells from faintness to clarity along with the increase of lati-tudes of the plant distributions, the climatic variation from moist to arid, the annual precipitation from more to less and the annual mean temperature from high to low. The fossil P. davidiana differs from the specimens collected from Shandan in semiarid to arid climatic regions but closely resembles the Wushan leaves in a semi-moist climatic area in a lot of fea-tures. In a word, the new research may reflect that the flora lives in a semi-moist climatic environment. The present dis-covery of compression of Paleogene Populus davidiana is of great significance to studying vegetation types, climatic and environmental changes during the primal uplifting of the Qinghai-Tibet Plateau.展开更多
Results of magnetopedostratigraphic study of three sections of loess in the LanzhouBasin are significant. (1) The oldest aeolian loess deposited on pediment in the Lanzhou Basindates back to 1.8 Ma, indicating the end...Results of magnetopedostratigraphic study of three sections of loess in the LanzhouBasin are significant. (1) The oldest aeolian loess deposited on pediment in the Lanzhou Basindates back to 1.8 Ma, indicating the end of erosion development. (2) The highest (also oldest)terrace T7 is identified and dated at about 1.7 Ma. Huang He began developing (about 1.8-1.7 Ma)after dissection of the pediment and before the oldest terrace formed. The incision rate of HuangHe varied with time. Its two peak periods are from 1.8 to 1.7 Ma BP and from 0.15 Ma BP topresent, corresponding to episodic uplift of the Tibetan Plateau.展开更多
基金supported by the National Natural Science Foundation of China(No.41290253)
文摘Here,we describe a new primitive Erinaceidae species,Oligoechinus lanzhouensis n.gen.n.sp.,based on a specimen from late Oligocene strata of the Lanzhou Basin,Gansu Province.Its characteristics are as follows:the M1 width is longer than the length,the metastyle extends far disto-labially,the posterior margin has strong curve and a distinct metaconule that is connected to the protocone by a postprotocrista is located in the centre of the tooth.The posterior arm of the metaconule is poorly developed.In the P4,the pterion of the metastyle is less developed and the metacone is carinate.In addition,O.lanzhouensis has a premolar larger than the canine tooth(P2>C)and P3 had no molarisation,characters also possessed by Erinaceus.Overall,O.lanzhouensis was similar to Mioechinus based on architectural tooth features,demonstrating a closed genetic relationship.Fossil Erinaceidae are relatively rare before the Miocene.The discovery of O.lanzhouensis provides an important insight into the origin of Mioechinus in China and the early evolution of the Erinaceidae.Our analysis shows that a relatively recent ancestor of Mioechinus had probably existed in the early Oligocene and that O.Lanzhouensis was likely an ancestral type of Mioechinus gobiensis,and its systematic position should be located at a transitional position between Amphechinus and Mioechinus.
基金This study was supported financially by the National Natural Science Foundation of China(Nos.41704071,41290253)the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(2019QZKK0707)+2 种基金Chinese Academy of Sciences“Light of West China”Program(XAB2018B04)Australian Research Council grant DP190100874We thank David Heslop for checking our reversal test result.
文摘The Quantougou(QTG) Fauna in central Lanzhou Basin is an important late Mid-Miocene fauna on the northeastern Tibetan Plateau margin,but its numerical age remains a matter of debate.Here,we present a new magnetostratigraphic record for a fluvio-lacustrine section to further constrain the age of the QTG Fauna.Results suggest that the studied section spans from polarity chrons C5Cn.2n to C5 n.2n or C5 An.1n,with ages of ca.16.5 Ma to 10 Ma or 16.5 Ma to 12 Ma.The QTG Fauna is located at the top of polarity chron C5r.3 r or C5 Ar.2 r,which corresponds to an age of 11.7 Ma or 12.8 Ma for the fauna.Accordingly,the associated Myocricetodontinae(a subfamily of Gerbillidae,Rodentia) is suggested to have appeared in the Lanzhou Basin at 11.7 Ma or 12.8 Ma,which is the oldest Myocricetodontinae in East Asia but is still much younger than the ~20 Ma appearance of this subfamily in West and South Asia.Our age data support the interpretation that East Asian Myocricetodontinae originated from South Asia.The QTG fauna further suggest a dry and open grassland environment,which is consistent with global cooling after the Mid-Miocene Climatic Optimum.
基金supported by the National Natural Science Foundation of China (Grant No. 41290253)
文摘The Asian monsoon-arid environment system began to develop during the Oligocene, but the exact position of the arid zone boundary is uncertain in the Oligocene. Fossil mammal assemblages can be used to assess the environment of an area. There were two sizes of mammals in the Nanpoping fauna from the Oligocene strata of the Lanzhou Basin： the small ones were grassland rodents such as Ctenodactylidae; the large ones were forest dwellers such as Paraceratherium and Paraentelodon. Of the 23 species of mammals identified in the Nanpoping fauna, -40% were forest dwellers and the rest （-60%） were grassland taxa. The Nanpoping fauna was compared with the contemporaneous Dingdanggou fauna in the Danghe area to the north and Jiaozigou fauna in the Linxia area to the south. The Nanpoping fauna contains elements of both other faunas and thus represents a transitional assemblage between forest and grassland. So, it can be inferred that the southern boundary of the arid zone in China during the Oligocene was probably near the Lanzhou Basin.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 49472083, 49572133 and 49972004) and the Institute Fund of ETH, Switzerland.
文摘The Tertiary deposits of the Yongdeng section, the Lanzhou Basin were studied by means of magnetostrati-graphy. The magnetostratigraphic sequences from Paleocene to Miocene were established, and the time scale for the corresponding stratigraphy and mammalian faunas was also established by referring to their correlation to the GPTS of BKSA95 (The geomagnetic polarity time scale which was thoroughly revised and updated by Berggreen et al. in 1995). In the end the paleoenvironmental records and their relationship with the uplifting of the Tibetan Plateau were discussed. The results are as follows. The top boundary of the Xiliugou Formation is dated to be 51 Ma, i.e. Eocene. TheYehucheng Formation covers the time span of 51-31.5 Ma, i.e. from late Early Eocene to early Early Oligocene. The Xianshuihe Formation covers the time span of 31.5-15 Ma, i.e. from Early Oligocene to Middle Miocene. The lower member of the Xianshuihe Formation spans from 31.5 to 20.0 Ma, i.e. from Early Oligocene to early Early
文摘An angiosperm compression flora is found in Palaeogene from Lanzhou Basin and the cuticular analysis of Populus davidiana Dode in the flora is carefully made. Fur-thermore, the fossil cuticles are compared with the epidermal structures of extant Populus leaves growing in different en-vironments, i.e. moist, semimoist, and semiarid to arid cli-matic regions. The present experiments indicate that mature leaves of P. davidiana show leaf size from big to small, leaf cuticles from thick to thin and anticlinal walls of epidermal cells from faintness to clarity along with the increase of lati-tudes of the plant distributions, the climatic variation from moist to arid, the annual precipitation from more to less and the annual mean temperature from high to low. The fossil P. davidiana differs from the specimens collected from Shandan in semiarid to arid climatic regions but closely resembles the Wushan leaves in a semi-moist climatic area in a lot of fea-tures. In a word, the new research may reflect that the flora lives in a semi-moist climatic environment. The present dis-covery of compression of Paleogene Populus davidiana is of great significance to studying vegetation types, climatic and environmental changes during the primal uplifting of the Qinghai-Tibet Plateau.
文摘Results of magnetopedostratigraphic study of three sections of loess in the LanzhouBasin are significant. (1) The oldest aeolian loess deposited on pediment in the Lanzhou Basindates back to 1.8 Ma, indicating the end of erosion development. (2) The highest (also oldest)terrace T7 is identified and dated at about 1.7 Ma. Huang He began developing (about 1.8-1.7 Ma)after dissection of the pediment and before the oldest terrace formed. The incision rate of HuangHe varied with time. Its two peak periods are from 1.8 to 1.7 Ma BP and from 0.15 Ma BP topresent, corresponding to episodic uplift of the Tibetan Plateau.
