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Causes and consequences of the Cambrian explosion

Science China Earth Sciences 2014年第6期57卷 930-942页

作者： ZHANG XingLiang shu degan State Key Laboratory of Continental Dynamics and Department of Geology Northwest University Early Life Institute Northwest University

The Cambrian explosion has long been a basic research frontier that concerns many scientific fields. Here we discuss the cause-effect links of the Cambrian explosion on the basis of first appearances of animal phyla in the fossil record, divergence time, environmental changes, Gene Regulatory Networks, and ecological feedbacks. The first appearances of phyla in the fos- sil record are obviously diachronous but relatively abrupt, concentrated in the first three stages of the Cambrian period （541- 514 Ma）. The actual divergence time may be deep or shallow. Since the gene regulatory networks （GRNs） that control the de- velopment of metazoans were in place before the divergence, the establishment of GRNs is necessary but insufficient for the Cambrian explosion. Thus the Cambrian explosion required environmental triggers. Nutrient availability, oxygenation, and change of seawater composition were potential environmental triggers. The nutrient input, e.g., the phosphorus enrichment in the environment, would cause excess primary production, but it is not directly linked with diversity or disparity. Further in- crease of oxygen level and change of seawater composition during the Ediacaran-Cambrian transition were probably crucial environmental factors that caused the Cambrian explosion, but more detailed geochemical data are required. Many researchers prefer that the Cambrian explosion is an ecological phenomenon, that is, the unprecedented ecological success of ruetazoans during the Early Cambrian, but ecological effects need diverse and abundant animals. Therefore, the establishment of the eco- logical complexity among animals, and between animals and environments, is a consequence rather than a cause of the Cam- brian explosion. It is no doubt that positive ecological feedbacks could facilitate the increase of biodiversity. In a word, the Cambrian explosion happened when environmental changes crossed critical thresholds, led to the initial formation of the meta- zoan-dor

关键词： Cambrian explosion dGRNs Gondwana environmental changes ecological snowball

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Acta Geologica Sinica(English Edition) 2018年第5期92卷 I0002-I0002,I0001页

作者： shu degan Acta Geologica Sinica

Dear Authors and Readers:First of all,on behalf of the new Editorial Board,I would like to express our sincere appreciation for your continuing support of our *** journal,founded in 1922,is the oldest geological journal in *** the flagship journal of the Geological Society of China,it has become more and more influential in earth sciences in China and

关键词： Message from the Editor-in-Chief

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Are hyoliths Palaeozoic lophophorates?

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National Science Review 2020年第2期7卷 453-469页

作者： Fan Liu Christian B Skovsted Timothy P Topper Zhifei Zhang degan shu State Key Laboratory of Continental Dynamics Shaanxi Key Laboratory of Early Life and Environments Department of Geology Northwest University Department of Palaeobiology Swedish Museum of Natural History

The phylogenetic position of hyoliths has long been unsettled, with recent discoveries of a tentaculate feeding apparatus(‘lophophore’) and fleshy apical extensions from the shell(‘pedicle’) suggesting a lophophorate affinity. Here, we describe the first soft parts associated with the feeding apparatus of an orthothecid hyolith, Triplicatella opimus from the Chengjiang biota of South China. The tuft-like arrangement of the tentacles of T. opimus differs from that of hyolithids, suggesting they collected food directly from the substrate. A reassessment of the feeding organ in hyolithids indicates that it does not represent a lophophore and our analysis of the apical structures associated with some orthothecids show that these represent crushed portions of the shell and are not comparable to the brachiopod pedicle. The new information suggests that hyoliths are more likely to be basal members of the lophotrochozoans rather than lophophorates closely linked with the Phylum Brachiopoda.

关键词： orthothecid the Chengjiang Lagerst¨atte Cambrian soft parts lophophore

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The earliest-known ancestors of Recent Priapulomorpha from the Early Cambrian Chengjiang Lagerstatte

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Chinese Science Bulletin 2004年第17期49卷 1860-1868页

作者： HAN Jian shu degan ZHANG Zhifei LIU Jianni Department of Geology and Key Laboratory for Continental Dynam-ics of the Education Ministry Northwest UniversityXi’an 710069China School of Earth Sciences and Resources China University of Geo-sciencesBeijing 100083China

The taxonomy of an early ancestor of Recent Priapulidae, Xiaoheiqingella peculiaris (= Yunnanpriapulus halteroformis Huang et al., 2004) from the Early Cambrian Chengjiang fossil Lagerst?tte, is revised. Morphological characters comprise a pair of caudal appendages rather than a single appendage flanking the trunk end and a possible urogenital duct found inside the preanal region. An addi- tional extremely rare fossil priapulid worm, Paratubiluchus bicaudatus gen. nov., sp. nov. is also described herein. Its diagnostic characters are: an introvert bearing 25 longitudi- nal rows of scalids, a distinct neck region, no annulus on the oval trunk, and a pair of caudal appendages. The proportion of body parts is similar in size to that of loricate larvae of Recent priapulids and larva-formed Palaeopriapulitidae. Taking account of the features of Xiaoheiqingella, bicaudal appendages are considered to be a synapomorphy of Pri- apulidae and Tubiluchidae. Paratubiluchus gen. nov. is most likely a candidate for the ancestor of the Tubiluchidae; it probably originated from a larva-formed priapulid with 25 rows of scalids, thus representing an intermediate link be- tween the priapulids in mature-form and the priapulids with lorica.

关键词： Early Cambrian Chengjiang Lagerstatte priapulids Xiaoheiqingella Paratubiluchus

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Acta Geologica Sinica(English Edition) 2015年第S1期 8-8页

作者： shu,degan Acta Geologica Sinica

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A venomous arthropod in the Early Cambrian Sea

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Chinese Science Bulletin 2011年第15期56卷 1532-1534页

作者： FU DongJing ZHANG XingLiang shu degan State Key Laboratory of Continental Dynamics Early Life Institute and Department of Geology Northwest University Xi' an 710069 China

A number of recently evolved animals possess poison glands for feeding and/or ***,examples of such animals are rare in the fossil *** report a fossil arthropod Isoxys curvirostratus from the Early Cambrian Chengjiang biota of *** species is regarded as the oldest known venomous arthropod based on the presence of venomous glands in its head *** adult animal is 2-5 cm long and the body is covered entirely with a *** presence of large stalk eyes and a pair of stout grasping appendages with a terminal spine suggest it was ***,the two pear-shaped,three-dimensionally preserved objects that are present in the head region and at the base of the grasping appendages closely resemble the venom glands of some living arthropods in size,shape,and *** features indicate that the presence of venomous predators could date back 520 million ***,our observations suggest that the feeding strategies and organs adapted for this purpose had already reached a high level of diversity and anatomical sophistication in the Early Cambrian ecosystems.

关键词：节肢动物有毒化石记录澄江生物群食肉动物生态系统寒武纪附属物

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Redox history of the Three Gorges region during the Ediacaran and Early Cambrian as indicated by the Fe isotope

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Geoscience Frontiers 2018年第1期9卷 155-172页

作者： Yusuke Sawaki Miyuki Tahata Tsuyoshi Komiya Takafumi Hirata Jian Han degan shu Department of Earth and Planetary Sciences Tokyo Institute of Technology Department of Earth Science and Astronomy Graduate School of Arts and Sciences The University of Tokyo Geochemistry Research Center The University of Tokyo Department of Geology and Key Laboratory for Continental Dynamics Northwest University

The Ediacaran-Cambrian transition is characterized by numerous events such as the emergence of large multi-cellular metazoans and surface environmental *** on geological evidence,it has been proposed that this transition coincided with the increase in the atmospheric oxygen level that was key to the evolution of *** though ancient redox conditions can be inferred from the composition of sedimentary iron mineral species,this method is not necessarily applicable to all *** the Earth system,the cycling of iron is of considerable interest owing to its sensitivity to redox *** regarding the paleo-oceanic iron cycle is revealed in the iron isotopic composition of ironbearing ***,only limited iron isotopic data exists for Ediacaran-to Cambrianperiod *** circumvent this deficiency,we drilled a fossiliferous Ediacaran to Early Cambrian sedimentary succession in the Three Gorges region,South *** analyzed the iron isotope ratios(δ^(56/54)Fe)of pyrite grains in the drill cores using laser ablation multi collector inductively coupled plasma mass *** results demonstrate large variations inδ^(56/54)Fe,from-1.6 to 1.6‰,and positive iron isotope ratios are observed in many *** presence of positiveδ^(56/54)Fe in pyrite indicates that the ferrous iron in the seawater was partially oxidized,suggesting that seawater at Three Gorges was ferruginous during the Ediacaran and Early Cambrian ***,aggregated pyrite grains in organic carbon-rich black shales at Member 4 of the Doushantuo Formation and the base of the shuijingtuo Formation yield near-zeroδ^(56/54)Fe values;this suggests that the ocean was transiently dominated by sulfidic conditions during these *** negativeδ^(56/54)Fe values,lower than-1‰,can be interpreted as a signature of *** DIR also might contribute in part to the re-mineralization of organic matter during the largest negative carbon isotope anoma

关键词： δ56/54Fe Pyrite Ediacaran Cambrian Three Gorges

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Dimorphism of Bivalved Arthropod Branchiocaris？ Yunnanensis from the Early Cambrian Chengjiang Biota, South China

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Acta Geologica Sinica(English Edition) 2016年第3期90卷 818-826页

作者： WU Yu FU Dongjing ZHANG Xingliang Allison C. DALEY shu degan Early Life Institute and State Key Laboratory of Continental Dynamics Department of Geology Northwest University Xi 'an 710069 China Department of Zoology University of Oxford South Parks Road Oxford OX1 3PS UK Oxford University Museum of Natural History Parks Road Oxford OX1 3PW UK

The bivalved arthropod Branchiocaris？ yunnanensis Hou, 1987 is redescribed on the basis of new fossil material from the early Cambrian Chengjiang biota, South China. In total, 81 specimens have been examined. The carapace comprises two identical valves, each valve are sub-circular in outline, ranging from 24 mm to 58 mm in length, and from 15 mm to 46 mm in height. The dorsal margin is straight and bears two short cardinal spines. The valve surface is either smooth or ornamented with polygonal reticular structures, which may result from different preservation conditions. Two morphotypes have been recognized based on the presence or absence of a subdorsal swelling of the valve, which is convex dorsolaterally and extends beyond the dorsal margin when it appears. Statistic and ontogenetic analyses show both morphotypes grow isometrically and have the same growth trajectory. Therefore, the two morphotypes are interpreted as dimorphism within the same species. Our results are helpful for investigating the taxonomy and ontogeny of arthropod fossils and suggest that dimorphism might be fairly common in these early arthropods.

关键词： Arthropoda Branchiocaris Dimorphism Ontogeny Chengjiang biota

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Comparative study of Cambrian lobopods Miraluolishania and Luolishania

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Chinese Science Bulletin 2008年第1期53卷 87-93页

作者： LIU JianNi shu degan HAN Jian ZHANG ZhiFei Early Life Institute and the Key Laboratory of Continental Dynamics Northwest University Xi'an 710069 China School of Earth Sciences and Resources China University of Geosciences Beijing 100083 China

The rare fossil Miraluolishania described by Liu et al. from the Lower Cambrian Chengjiang Lagersttte in 2004 is regarded as an arthropod sphinx because it bears mosaic features of both lobopods and arthropods. The discovery of this rare transitional form offers direct fossil evidence for exploring the relationship between lobopods and arthropods. However, some scientists consider Miraluolishania to be a junior synonym of Luolishania because the former superficially resembles the latter in general appearance. Considering the significant differences between the two taxa, a thorough comparative study of Miraluolishania and Luolishania leads to the conclusion that there are definitely two different genera. Nevertheless, the "Luolishania" of the Haikou area is indeed "Miraluolishania", whereas Luol-ishania is most likely the typical genus of the Maotianshan area of Chengjiang County.

关键词：寒武纪化石古生物特征

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Origin of raptorial feeding in juvenile euarthropods revealed by a Cambrian radiodontan

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National Science Review 2018年第6期5卷 863-869页

作者： Jianni Liu Rudy Lerosey-Aubril Michael Steiner Jason A. Dunlop degan shu John R. Paterson Shaanxi Key Laboratory of Early Life and Environment The Key Laboratory of Continental DynamicsDepartment of Geology Northwest University Palaeoscience Research Centre School of Environmental and Rural ScienceUniversity of New England Institut für Geologische Wissenschaften 4. Museum für Naturkunde Leibniz Institute for Evolution and Biodiversity Science

The rapid rise of arthropods during the Cambrian quickly established some clades, such as the euarthropod stem-group called Radiodonta, as the dominant and most diverse predators in marine ecosystems. Recent discoveries have shown that the size and dietary ecology of radiodontans are far more diverse than previously thought, but little is known about the feeding habits of juveniles. Here, we document a very small(～18-mm-long), near-complete specimen of the radiodontan Lyrarapax unguispinus from the early Cambrian Chengjiang Biota of China. This specimen is the smallest radiodontan individual known,representing a juvenile instar. Its adult-like morphology—especially the fully developed spinose frontal appendages and tetraradial oral cone—indicates that L. unguispinus was a well-equipped predator at an early developmental stage, similar to modern raptorial euarthropods, such as mantises, mantis shrimps and arachnids. This evidence, coupled with the basal phylogenetic position of radiodontans, confirms that raptorial feeding habits in juvenile euarthropods appeared early in the evolutionary history of the group.

关键词： Lyrarapax Radiodonta Arthropoda Cambrian predation feeding ecology

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