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This paper focuses on jointly inferring network and community structures from the dynamics of complex systems. Although many approaches have been designed to solve these two problems solely, none of them consider explicit shareable knowledge across these two tasks. Community detection (CD) from dynamics and network reconstruction (NR) from dynamics are natural synergistic tasks that motivate the proposed evolutionary multitasking NR and CD framework, called network collaborator (NC). In the process of NC, the NR task explicitly transfers several better network structures for the CD task, and the CD task explicitly transfers a better community structure to assist the NR task. Moreover, to transfer knowledge from the NR task to the CD task, NC models the study of CD from dynamics to find communities in the dynamic network and then considers whether to transfer knowledge across tasks. A test suite for multitasking NR and CD problems (MTNRCDPs) is designed to verify the performance of NC. The experimental results conducted on the designed MTNRCDPs have demonstrated that joint NR with CD has a synergistic effect, where the network structure used to inform the existence of communities is also inherently employed to improve the reconstruction accuracy, which, in turn, can better demonstrate the discovering of the community structure. The code is available at: https://github.com/xiaofangxd/EMTNRCD., Comment: This work has been submitted to the IEEE TAI for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessible

Origin and early evolution of animal development remain one of many deep, unresolved problems in evolutionary biology. As a compelling case for the existence of pre-Cambrian animals, the Ediacaran embryo-like fossils (EELFs) from the Weng'an Biota (approx. 609 Myr old, Doushantuo Formation, South China) have the great potential to cast light on the origin and early evolution of animal development. However, their biological implications can be fully realized only when their phylogenetic positions are correctly established, and unfortunately, this is the key problem under debate. As a significant feature of developmental biology, the cell division pattern (CDP) characterized by the dynamic spatial arrangement of cells and associated developmental mechanisms is critical to reassess these hypotheses and evaluate the diversity of the EELFs; however, their phylogenetic implications have not been fully realized. Additionally, the scarcity of fossil specimens representing late developmental stages with cell differentiation accounts for much of this debate too. Here, we reconstructed a large number of EELFs using submicron resolution X-ray tomographic microscopy and focused on the CDPs and associated developmental mechanisms as well as features of cell differentiation. Four types of CDPs and specimens with cell differentiation were identified. Contrary to the prevailing view, our results together with recent studies suggest that the diversity and complexity of developmental mechanisms documented by the EELFs are much higher than is often claimed. The diverse CDPs and associated development features including palintomic cleavage, maternal nutrition, asymmetric cell divisions, symmetry breaking, establishment of polarity or axis, spatial cell migration and differentiation constrain some EELFs, if not all, as total-group metazoans.This article is part of the theme issue ���How Chinese fossils and palaeontological research impact our understanding of major evolutionary transitions���.

The Early Cambrian Maotianshan Shale, exposed near Kunming, China, is one of the oldest and best-preserved Konservat Lagerstatten, containing the Chengjiang Biota. Although the fossils have been well-studied, the depositional processes and stratigraphic relationships amongst the fossil-bearing localities are poorly understood, largely due to limited continuous exposures and structural complexity in this area. In this study we use a detailed facies and stacking pattern analysis to delineate the depositional history and stratigraphic relationship of the Maotianshan. Sedimentologic observations from five prolific fossil localities of the Chengjiang Biota have yielded six distinct facies within the Maotianshan Shale. The three coarse-grained facies, composed of siltstones and very fine sandstones (F1–F3), contain sedimentary structures including hummocky cross stratification and combined flow ripples that are consistent with deposition within storm wave base. The fine grained facies, composed of interbedded silty mudstones and clay-rich mudstones (F4–F6), were deposited below the wave base and represent episodes of lower storm frequency and pelagic sedimentation. These six facies have specific stacking patterns, indicating the presence of five distinct depositional units. Each of those depositional units is bound on its upper and lower contact by a flooding surface. Fining-upward successions near the base of each stratigraphic unit are interpreted as short-lived marine transgressions; these are overlain by coarsening-upward stacked facies interpreted as a period of shoreline progradation. The fossils of the Chengjiang fauna are exclusively found in the coarsening-upward part of the depositional units. The oldest fossil-bearing intervals are associated with the most westerns sections in the study area. In contrast, the youngest fossil-bearing intervals are found in the most eastern sections. This time-transgressive relationship is interpreted to reflect a genetic relation between distinct sedimentary processes and environments, and the burial and preservation of the Chengjiang Biota.

Feldspar and clastic debris are the most important constituent framework grains of sedimentary clastic rocks and their chemical dissolution plays an essential role in the formation and evolution of the secondary pore in the reservoir rocks. On the basis of thermodynamic phase equilibrium, this study investigates the chemical equilibrium relationships between fluid and various plagioclase and K-feldspar in diagenesis of the sediments, particularly, the impact of temperature and fluid compositions (pH, activity of K+, Na+, Ca2+and so on) on precipitation and dissolution equilibria of feldspars. Feldspar is extremely easily dissolved in the acid pore water with a low salinity when temperature decreases. The dissolution of anorthite end-member of plagioclase is related to the Ca content of the mineral and the fluid, higher Ca either in the mineral or in the fluid, easier dissolution of the feldspar. Moreover, the dissolution of albite end-member of plagioclase is related to Na of both the mineral and fluid, lower Na out of both the mineral and fluid, easier dissolution of the mineral. Similarly, lower-K fluid is more powerful to dissolve K-feldspar than the higher. The anorthite component of plagioclase is most easily dissolved in ground water-rock system, the albite is the secondary, and K-feldspar is the most stable. Selective dissolution of plagioclase occurs in diagenesis because of the plagioclase solid solution that is mainly composed of albite and anorthite end-members, Ca-rich part of which is preferentially dissolved by the pore water, in contrast to the Na-rich parts. Based on investigation of reservoir quality, secondary pore, dissolution structures of feldspar, clay minerals and ground water chemistry of the Kela 2 gas field of Kuqa Depression in the Tarim basin of Western China, we discovered that the secondary pore is very well developed in the highest quality section of the reservoir, and the plagioclase of which was obviously selectively dissolved, in contrast to the overgrowth of K-feldspar. Chemistry of the ground water out of the highest quality section of the reservoir is consistent with the complete dissolution field of anorthite, partial dissolution field of albite component of plagioclase, and the precipitation of K-feldspar on the temperature-logK phase equilibrium diagram drawn from this study. The thermodynamic modeling calculation gave us an insight into formation of the secondary pore within the reservoir, and the dissolution of plagioclase an important cause of the secondary pore. It is assumed that the solvent to dissolve the plagioclase frame grains originated from the origin-enriched compacted fluid acids out of the mudstone buried beneath the top of geopressured zones in the Kuqa Depression.

Totally 19 samples of typical Upper Proterozoic-Lower Cambrian sedimentary rocks were collected and analyzed for an organic geochemical investigation. Almost all these rocks have high TOCs, super-maturities and similar biomarker distribution. As an exception, however, the Sinian Nantuo Tillite shows much lower TOCs and little phytane and pristane in comparison with those in other strata, which implies a very faint photosynthetic process, and a restricted euphotic zone and quite limited sunlight within the sedimentary water column during the Sinian glaciation age in the western Yangtze region providing an evidence for palaeo-oceanic environment of the Neoproterozoic Snowball Earth age.

Cindarella eucalla Chen et al. from the Early Cambrian Chengjiang fauna is the closest relative of Xandarella spectaculum Hou et al. Cindarella and Xandarella are united as Xandarellida, a further component of Cambrian arachnate diversity. Diagnostic of Xandarellida are ventral eyes, a posterior extension of the head shield that covers anterior trunk segments, and multiple somites per tergite in the rear part of the trunk. Somites and tergites are decoupled throughout the trunk in Cindarella. The bilobate structure of the exopod in xandarellids is widespread throughout the Arachnata.

An onychophoran-like fossil animal, Paucipodia inermis gen. et sp. nov., is described from the Lower Cambrian Chengjiang lagerstatte in Yunnan, China. The animal was soft-bodied, and possessed six pairs of unjointed legs, each having two claws distally. The body was finely annulated, lacked trunk plates, and apparently terminated posteriorly with the last leg pair, without preserved evidence of a posterior trunk extension. Paucipodia widens the morphological range hitherto known in Cambrian lobopodians, notably regarding leg number and presence or absence of plates. Its morphology also provides support for the recently suggested anteroposterior orientation of Hallucigenia and Microdictyon.

A bed-by-bed record of a 92m thick section through the Arenig to lower Ashgill at Daping near Yichang, Yangtze Platform, is the first Ordovician section from China to be presented internationally in this detail. The predominant facies is identical to what is known in northern Europe as Orthoceratite limestone. Among features shared between the Chinese and Baltoscandian carbonate facies are frequently occurring, bored and/or burrowed, mineralized discontinuity surfaces, buckled beds, perched cephalopod conchs, thin seams of small ferrugineous stromatoids, and biocalcarenitic components dominated by arthropods and echinoderms. The Chinese as well as the Baltoscandian sections show evidence of a major regression about the transition from the Arenigian to the Llanvirnian. Contrasting with Baltoscandian sections, the Daping section begins with tropical to subtropical carbonate platform facies.

This paper provides a brief outline of the current, detailed inter-disciplinary work on the Xiaoyangquiao section, trying to expose all the aspects for reference tied to the Global Single Stratigraphic Point (GSSP) Concept for defining the Cambrian–Ordovician Boundary. The 45 m critical interval of this section outcrops very well along the steep bank of a stream and is free from folding, faulting, intrusions, and has not been affected by weathering. Colour alternation of conodonts and acritarchs, and crystallinity indices of illite all indicate a maximum thermal grade of 100 °C. The lithofacies, being of great lateral persistence for a hundred kilometres, consists mainly of a rhythmical sequence of lime mudstone and shales deposited in a moderately deep outer shelf environment of quiet water, well below the normal storm wave base. Chemical investigation of the rocks demonstrates strong positive correlation between A12O3content and those of K2O, MgO, Fe2O3, TiO2, Be, Cr, Co, Ni, Zn and Ba, indicating these components are tied to the clay fractions. A stable depositional environment is demonstrated by the uniform chemistries through the boundary interval. Close to the boundary itself P2O5contents are low, indicating continuous sedimentation at fairly substantial rates.The major biological events, the biostratigraphic framework, and the stratigraphic range of conodont, graptolite, trilobite, and acritarch taxa are illustrated briefly with diagrams. Following the majority views of the Calgary Plenary Session, the boundary level is to be chosen at a point marked by the First Appearance Datum (FAD) of the selected conodont taxon or taxa in the vicinity of the level close to, but below, the first influx of nematophorous graptolites. The following four points marked by the incoming of conodont taxon or taxa are recommended for consideration of the ‘Golden Spike'‘: (1) FAD ofCordylodus intermediusat 5.28 m below the first influx of nematophorous graptolites; (2) FAD ofHirsutodontus simpler–Cordylodus drucei–Albiconus postcostatusat 5.23 m; (3)FADofSemiacontiodus lavadamensis–Utahconus utahensis–Monocostodus sevierensisat 3.85 m; (4)FADofCordylodus lindstromiat 2.23 m. For the following reasons the FAD ofH. simplex–C. drucei–A. postcostatusis favoured: (1) the taxa are all distinct and widely dispersed; (2) intensive evolutionary change took place in conodonts, graptolites, trilobites and acritarchs prior to or after this point; all the fossil groups occur together, providing correlation with many regions throughout the world; (3) the point is in a position between the previously widely accepted boundary levels based on graptolites and trilobites; (4) the proposed point lies within a thin, laterally persistent, rhythmical sequence. The FAD ofCordylodus lindstromiis also a favourable point, sharing many advantages mentioned above. But this point is less satisfactory in being defined by the FAD of a single taxonC. lindstromiwhich also has an extremely small population size.An isochron age of 500.7 ± 7.4 Ma is determined from clay fractions of mudstones 8.5 m below the proposed point by means of the Rubidium–Strontium method.The ɛND signature determined from conodonts, trilobites hyolithids and acrotretid brachiopods has a mean value of −6.7, comparable with that of the coeval oceanic water mass occupying southeastern North America and Europe, and indicating that northeastern China bordered the same ocean. The mean Tdm model age determined was 1.26 Ga at the time of sedimentation, compatible with the mean Tdm model age of approximately 1.1 Ga for the Pacific Ocean today. The relatively low value of the Tdm model age indicates a substantial input from young orogenic volcanic island arcs and terranes.