中国北方上新世降温事件及其对温度纬度梯度变化的影响

中晚上新世是现代气候形成过程根据在同一地区(剖面)获得的古地磁年代资料,发现山西榆社及河北泥河湾的孢粉资料记录了在松山/高斯极性事件界线附近(约2.5 Ma)的一次明显的降温事件.山西榆社的孢粉资料还记录了在约2.7 Ma-2.8 Ma的一次降温事件.这些降温事件主要是因为全球性气候变化引起的,北极圈附近和西伯利亚的冷高压大大地降低了我国,特别是我国北方的冬季气温.与此同时,位于北极圈附近的阿拉斯加发生了更为强烈的降温事件.比较两地相当时期的降温幅度,可以发现因为不同纬度的降温幅度不同使得温度的纬度变化梯度比降温事件发生前大大增加了,由原来的纬度每增加一度降低约0.3℃增大到约0.5℃.     

New Cambrian lobopods and chaetognaths of the Siberian Platform

The association of isolated remains of lobopods with a netlike structure, including plates of Microdictyon rozanovi sp. nov. and sclerites with spinelike process of Onychomicrodictyon spiniferum gen. et sp. nov., as well as saberlike sclerites of Protohertzina yudomica sp. nov. interpreted as grasping spines of chaetognaths, is described from the middle part of the Inikan Formation of the Toyonian Stage of the Lower Cambrian (Lermontovia dzevanovskii Zone). The diagnoses and species composition of the genera Microdictyon and Protohertzina are refined.     

Lower-Middle Cambrian boundary in open shelf facies of the Siberian Platform

In the Early and Middle Cambrian (of traditional usage), three broad facies belts were developed over the Siberian Platform. The lithofacies belts comprise evaporitic-carbonate, reef-shoal, and open-marine environments.Trilobites assemblages are most diverse in the open-marine lithofacies (Judoma-Olenek facies), represented especially by the Kuonamka Formation, in the eastern part of the platform. Species, genera and families of trilobites gradually increased through the Middle-Cambrian boundary interval in the Kuonamka Formation. Protolenidae dominated in the time represented by the Lermontovia Zone. In strata assigned to the Anabaraspis Zone, the protolenids disappear, the paradoxidids appear, and the diversity of dorypygids increases. The number of trilobite families increases in the Oryctocara and Kounamkites zones.Well represented in the Kuonamka formation of the eastern Siberian Platform are three levels of trilobites that have potential for global correlation. They are the Oryctocephalus reticulatus (=O. indicus latus), Oryctocephalus indicus, and Ovatoryctocara granulatus levels. The Lower-Middle Cambrian boundary in the South China correlates to the lower part of the Kounamkites Zone of the Siberian Platform.     

New radiolarians from the Devonian of the southern Ural Mountains: 1. Early-Middle Devonian (Late Emsian-Early Eifelian)

Late Emsian-Early Eifelian radiolarians from the southern Ural Mountains are recorded and described for the first time. They come from the Kamennaya Gora section on the Tanalyk River near the town of Buribay, Bashkiria. The new Late Emsian-Early Eifelian radiolarian assemblage consists of 20 species of 11 genera of spherical, discoidal, spindle-shaped, pylomate, and spiny radiolarians. Four new species, i.e., Entactinia rostriformis sp. nov., Palaeodiscaleksus tumefactus sp. nov., Primaritripus buribayensis sp. nov., and P. chuvashovi sp. nov., are described. The diagnosis of the genus Primaritripus Afanasieva, 2000 is amended. The fact that the oryctocenosis is dominated by discoidal radiolarians suggests that, in the Late Emsian-Early Eifelian, the area under study was occupied by a relatively shallow marine basin. Based on radiolarians, a new Upper Emsian-Lower Eifelian biostraton, beds with Primaritripus buribayensis-Entactinia rostriformis, is established. The history of the study of Early Devonian radiolarians is considered.     

Modelling the Transport of Nutrients in Early Animals

The single-celled ancestors of multi-cellular animals (metazoans) did not need to transport nutrients between cells, but this ability is vital for modern animals. How could intercellular nutrient transport have begun? And how did this influence the early evolution of animals? In this hypothesis, I suggest that nutrients could have passed directly between the cytoplasm of conjoined cells in early compacted cell-balls, along the plane of the closed epithelium. This would have limited early animals to the size and form of modern embryos. The mechanisms that indirectly transport nutrients between discrete cells, via the extracellular fluid within the body-space, are modelled to have evolved sequentially; so comparison of nutrient transport processes could provide evidence of any early divergences of phyla. When the last of the indirect intercellular transport processes for essential nutrients had been developed, the extracellular fluid within the body-space would have contained all necessary nutrients. Then the epithelium could have greatly expanded, and cells lived and divided within the body-space. This development of nutrient transport processes would have enabled animals to greatly increase in size and complexity.     

The ontogeny of the Late Permian terebratulids (Brachiopoda) Gruntelasma Smirnova, Grigorjevaelasma Smirnova, and Campbellelasma Smirnova and their taxonomic position

A specific type of ontogenetic change combining elements of dielasmoid and angustothyridid stages of brachidium development is established for the Late Permian genera Gruntelasma Smirnova, 2004, Grigorjevaelasma Smirnova, 2004, and Campbellelasma Smirnova, 2004 from the Russian Platform. On this basis, these genera are assigned to the superfamily Compositelasmatoidea Smirnova, family Compositelasmatidae.     

Lower Cambrian Small Shelly Fossils of northern Sichuan and southern Shaanxi (China), and their biostratigraphic importance

Extensive information has been acquired on the occurrence of Lower Cambrian Small Shelly Fossils (SSF) in the shallow water sediments of the western fringe of the Yangtze Platform (eastern Yunnan and central Sichuan Provinces) during the last two decades. However, less is known on the temporal and spatial distribution of SSFs on the northern margin of the Yangtze Platform. Here we report SSF associations from Kuanchuanpu (Ningqiang County, southern Shaanxi Province), Shatan, and Xinli (both Nanjiang County, northern Sichuan Province) representing the Southwest Shaanxi region and from Sanlangpu, and Xiaowan (Xixiang County, southern Shaanxi Province) of the Southeast Shaanxi - Northwest Hubei region. The thickness of the Lower Cambrian SSF-bearing strata strongly decreases in this region from West to East and the stratigraphic hiatus increases. An earliest Cambrian hiatus is widely distributed on the northern margin of the Yangtze Platform. At the same time, a syngenetic brecciation occurred in wide shallow shelf settings. A tectonic mobilization, possibly related to the assembly of Gondwana following the breakup of Rodinia, may be responsible for this. In sections near Kuanchuanpu (Ningqiang County), the Meishucunian (equivalent to the Nemakit-Daldynian to Tommotian of Siberia) succession comprises ca. 55 m of dark phosphatic carbonates, siltstones, and cherts. The SSF associations are similar to those of East Yunnan and, in ascending order, can be discriminated into the Anabarites trisulcatus - Protohertzina anabarica Zone, the Watsonella yunnanensis Zone (previously mentioned as Heraultipegma yunnanensis Zone), and the Sinosachites flabelliformis - Tannuolina zhangwentangi Zone. The Siphogonuchites triangularis - Paragloborilus subglobosus Zone cannot be unambiguously detected in the Southwest Shaanxi region. The occurrence of embryos and eggs within the Anabarites trisulcatus - Protohertzina anabarica Zone, which has been reported earlier, is remarkable. The previously reconstructed life cycle and taxonomic treatment of Olivooides / Punctatus are re-discussed. The earliest SSF associations (Anabarites trisulcatus - Protohertzina anabarica Zone to Watsonella yunnanesis Zone) are missing in the Southeast Shaanxi - Northwest Hubei region and the Ninella tarimensis - Cambroclavus fangxianensis Assemblage Zone and Rhombocorniculum cancellatum Taxon Range Zone are introduced herein.     

Tumulduria incomperta and the case for Tommotian trilobites

The enigmatic fossil Tumulduria incomperta Missanhevsky 1969 from the basal Tommotian Stage at 'Dvortsy' on the Aldan River, Siberian Platform, is reinvestigated in light of the report (Fedorov et al. 1979, Dokl. AN SSSR 249) of trilobite remains from the same beds. Comparisons of these supposed trilobites with old and new collections from 'Dvortsy' leave no doubt that they are identical to Tumulduria incomperta. Tumulduria is represented by phosphatic plates with a crude bilateral symmetry, consisting of a central longitudinal rounded ridge flanked by flat lateral portions. They are built of growth lamellae overlapping each other along the axis of symmetry. The surface carries prominent transverse folds and lamellar terminations. There is considerable morphological variation, and the similarity of some specimens to trilobites is only superficial. Tumulduria is interpreted as a bilaterally symmetrical metazoan with a dorsal protective plate; it probably represents a short-lived group that left no descendants.