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Little is known regarding characteristics and evolution of radiolarian fossils in the early Cambrian due to its rarity and poor preservation. Here we report a new radiolarian fauna from the Cambrian Shuijingtuo Formation corresponding to the Chiungchussuan Stage (Cambrian Series 2) in western Hubei, China. It contains over 300 radiolarian tests and these fossils belong to 4 morphotypes, including Paraantygopora porosa gen.et sp. nov., Braunosphaera sinensis gen.et sp. nov., Tetrasphaera? sp. and incertae spherical radiolarians. In taxonomy, Spumellaria predominates in the fauna and comprises 92% of the total. In shell structure, about 73% of all specimens are similar to the early Ordovician radiolarian fossils, with the shell walls characterized by perforated plate structures. The spherical radiolarians with latticed shells constitute another feature of the early Cambrian radiolarian fauna. The radiolarian fauna reported here contains many fossil specimens and covers different taxonomical taxa. These specimens usually consist of distinctive concentric multi-layers with complex structure. These characteristics indicate that Radiolaria had already thrived during the Cambrian Chiungchussuan Stage (Series 2, Stage 3), which may have occurred synchronously with the explosion and prosperity of macrobiota recorded in the strata deposited in shallower water condition. [ABSTRACT FROM AUTHOR]

Radiolarians are usually abundant in chert sequences and they have thus been widely used for the biostratigraphy of deep-water sediments. However, there are many difficulties in the correlation of radiolarian biostratigraphic schemes with the standard conodont zones. In this study, 21 radiolarian species were extracted from the Gufeng Formation that crops out in the Luojiaba (LJB) section (western Hubei, China), together with 5 co-occurring conodont species. In this way, it is the first time that the Pseudoalbaillella globosa , Follicucullus monacanthus and F. scholasticus radiolarian zones can be directly correlated with the Jinogondolella nankingensis gracilis , J. aserrata and J. postserrata conodont zones. Accordingly, the 3 radiolarians zones are now firmly correlated with the Roadian to middle Capitanian interval (Middle Permian). [ABSTRACT FROM AUTHOR]

Abundant metazoans phyla made their first appearances in the fossil record during a relatively short time span in the Ediacaran-Cambrian interval (560–520 Ma) and rapidly expanded ecologically during the early Cambrian, leading to the establishment of metazoan-dominated ecosystems accompanied by widespread biomineralization. This unique evolutionary event was known as the 'Cambrian Explosion'. Although a significant amount of work has been undertaken to understand the evolution of life during this time interval, previous studies have mainly focused on fossil records from the Cambrian fine-grained clastic rocks deposited in shallow-water environments. However, fossil records from marlstones and mudstones formed in deep-water basins were poorly understood. In this study, we focus on fossil records from the black thin-bedded marl and calcareous mudstones of the lower Cambrian Shuijingtuo Formation in the Three Gorges area, Hubei Province. A total of 9059 fossil specimens, including both microfossils and megafossils belonging to 45 species and 14 major taxonomic groups were recovered from the Shuijingtuo Formation at the Luojiacun section. Four palaeoecological assemblages were recognized based on fossil composition and ecological characteristics. The oldest assemblage (Assemblage A) features an Isoxys -dominated planktonic community with only one benthic group of bradoriids and exhibits the highest fossil abundance and lowest species diversity. Assemblage B is characterized primarily by highly diverse benthic groups, which in decreasing order of abundance include bradoriids (27.4%), sponge spicules (9.8%), cnidarians (5.7%) and hyoliths (2.0%). The third assemblage (Assemblage C) introduces the predominant role of sponge spicules, which compose 44.8% of the community. In contrast, Assemblage D is predominated by phytoplankton featuring the lowest fossil abundance and low diversity. Integration with geochemical and sedimentary data indicates that these biotic assemblages and their evolution were mainly controlled by environmental redox variations and changes in terrestrial fluxes and water depth, subsequently suggesting a significant role of these factors on biotic evolution in the early Cambrian deep-water environment. This study provides support for the importance of oxygen levels in the evolution of life during the early Cambrian. • Four palaeoecological assemblages were recovered from the Shuijingtuo Formation. • Redox, terrestrial fluxes and sea level change were considered the main controls. • Significance of oxygen content were implied on the evolution of early life. [ABSTRACT FROM AUTHOR]

The Permian radiolarian zones and their correlations with conodont zones or other chronostratigraphic schemes are still under debate. In this study, four genera, 21 species and two subspecies of radiolarians together with one genus and six species of conodonts were recovered from the Linghao Formation cropping out at the Longwangpo (LWP) section, northwestern Guangxi, South China. Six radiolarian interval zones and one abundance zone are recognized in the section, namely in ascending order, the Follicucullus scholasticus, Albaillella cavitata, A. protolevis, A. levis, A. excelsa, A. triangularis Interval zones and A. yaoi Abundance Zone. They are correlated with the Clarkina dukouensis, C. guangyuanensis and C. orientalis conodont zones recognized at the same section. Based on our data, the F. scholasticus Interval Zone and the lowermost part of A. cavitata Interval Zone are recognized to be upper Capitanian age, whereas the four Albaillella Interval zones are of Lopingian age (Wuchiapingian to the late Changhsingian). Two previously known Changhsingian radiolarian zones, namely the A. triangularis and A. yaoi Interval zones, should be extended down to the uppermost Wuchiapingian in this studied section. [ABSTRACT FROM AUTHOR]