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2020, Volume 27 Issue 6
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Core value of the Chengjiang fauna: formation of the animal kingdom and the birth of basic human organs SHU Degan, HAN Jian 2020, 27(6): 1-27.  DOI: 10.13745/j.esf.sf.2020.6.15 Abstract ( 1021 )   HTML ( 19 )   PDF (15933KB) ( 816 )   Well known for its abundant and extraordinary soft-tissue fossils, the Chengjiang fauna has witnessed the main phase of the Cambrian explosion and the first great congress of the ancestors of nearly all major phyla of animals on Earth. The large-scale survey and exploration of the fauna by Chinese paleontologists, partly in collaboration with international scientists, over the past 30 years can be broadly divided into three stages. In the first decade since 1984 (1984-1994), a large number of invertebrates, including basal animals and the protostomes of the early animal tree were discovered, but the subkingdom Deuterostomia was completely unknown. Then in the second decade (1995-2005), the great discoveries of various deuterostomes led to the construction of the basic framework of the Deuterostomia and then to the formation of the tripartite phylogenetic trees of early animals (TPTEA, including basal animals, protostomes and deuterostomes), for the first time. In the third decade (after 2005), the academic community began to think about the internal relationships between the formation of TPTEA and the multi-episode Cambrian explosion, leading to the new hypothesis of the three-episode Cambrian explosion. The Chengjiang fauna is important for deciphering the fauna structure, paleoecological environment, and so on. However, its core academic values mainly rest on two aspects. Firstly, The Chengjiang fauna, as the main phase witness of the Cambrian explosion, has created a nearly complete phylogenetic framework of the TPTEA on Earth for the first time. The three-phase radiation hypothesis reveals the essential connotation of the Cambrian explosion: a step-wise divergent evolution of animals, from basal to highly advanced groups, lasting about 40 million years. In the first phase, it gave birth to a bulk of basal animals (including some now extinct “animal” groups) in the latest Ediacaran, probably including some pioneer protostomes. The second phase took place in the first epoch of the Cambrian period (Terreneuvian), giving rise to the main invertebrate protostomes with a persistent prosperity of basal animals. The third phase proceeded in Cambrian Epoch 2 (represented by the Chengjiang fauna), which not only maintained the prosperity of basal animals and protostomes, but also, more importantly, gave birth to all the main phyla of the subkingdom Deuterostomia. Thus, the rudimental framework of the whole TPTEA has been shaped, with the termination of the major innovation events of the Cambrian explosion. Here, we discussed the evolutionary properties of Ediacaran biota, small shelly fossils and the Chengjiang fauna in the Cambrian explosion with emphasis on the biological properties of several important animal groups. The order Myllokunmingiida is the only known oldest vertebrate, while Yunnanozoon and Haikouella are neither vertebrates nor stem-group chordates but a special group of basal deuterostomes; Cheungkongella is a credible ancestor of the urochordate and it supports the classical hypothesis on the origin of the urochordates; and the gill slits were first invented in the members of the phylum Vetulicolia to provide key information on the origin of the deuterostomes. The second core value of the Chengjiang fauna is of profound humanistic and philosophical significance: the discoveries of the ‘first gill openings’, ‘first brain’, ‘first vertebrae’ and ‘first heart’ provide the pivotal evidence for solving the unsolved mystery of the origin of the main basic human organs as described in Darwin’s “The Descent of Man”. In addition, the morphological and anatomical information of the Chengjiang fauna can provide important clues for a better understanding of most components of Ediacaran and Cambrian metazoans. Figures and Tables | References | Supplementary Material | Related Articles | Metrics

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Ecological diversity in the terminal Ediacaran Gaojiashan biota HUA Hong, CAI Yaoping, MIN Xiao, CHAI Shu, DAI Qiaokun, CUI Zaihang 2020, 27(6): 28-46.  DOI: 10.13745/j.esf.sf.2020.6.2 Abstract ( 438 )   HTML ( 12 )   PDF (48223KB) ( 423 )   Ediacaran fossils mark a pivotal position in the evolution of life as it transitions between the predominantly microbial ecosystems of the Precambrian and the animal ecosystems of the Phanerozoic. Ediacaran communities were dominated by sessile epibenthos and their ecological structures were relatively simple. Many modern feeding modes such as macropredation, epibiosis, and interspecific competition or mutualism were absent or poorly represented. It is generally accepted that the soft-bodied Ediacara biota is part of a “failed” evolutionary experiment and it has no clear genetic relationship with Phanerozoic organisms. However, corresponding to the evolution of typical Ediacaran soft-bodied biota, there was a great proliferation of tubular animals at the end of the late Neoproterozoic, represented by the Gaojiashan biota, where Lagerstätte fossil deposit hosts a variety of soft-bodied or lightly biomineralized tubular fossils (Shaanxilithes, Gaojiashania, Sinotubulites, Conotubus, and Cloudina), calcareous microfossils (Protolagena), and calcareous cyanobacteria. Unlike other Ediacara fossil assemblages, the Gaojiashan biota is dominated by benthic sessile suspension feeders or detritus feeders. Of them, Cloudina is a millimetre-scale conical tube tapering adapically from an aperture to a rounded apex. The bulk of the tube is constructed by a series of successively stacked, repetitive, unevenly spaced, and funnel-shaped tube wall units. Cloudina occupied an epibenthic suspension-feeding life-mode, with the apex anchoring to microbially bound muddy substrate and the aperture extending upwards into the water column. Conotubus is a centimetre-sized conical tube consisting of a series of nested cylindrical-to-funnel-shaped tube walls (cylinders hereafter). This conotubular construction of nested cylinders is similar to that of the late Ediacaran fossil Cloudina. Integrated morphological, taphonomic and palaeoecological data suggest that it likely employed an epibenthic life-mode, with the apex anchoring to the muddy substrate and the aperture extending upwards into the water column and it was probably a suspension-feeding organism. Gaojiashania is a centimetre-size tube that consists of a series of repeating units. Each unit consists of a rigid ring and a flexible bucket-shaped tube wall. Each tube maintains a constant diameter and the rigid ring elements typically range from 1 to 2 mm in length, whereas the bucket components are more varied at 0.5-5 mm in length and are ornamented with transverse annuli. Gaojiashania, however, may have been a procumbent epibenthos, possibly with the rings anchoring to microbially bound muddy substrate. Sinotubulites are characterized by millimetre-to centimetre-size multilayer tubes open at both ends. The tube consists of two morphologically different walls: a multilayer inner wall with weak ornamentation, and a multilayer outer wall with transverse or oblique corrugations and sometimes longitudinal ridges. Surface ornamentation and polygonal shape of the cross-section suggest that Sinotubulites probably lived as an epibenthos lying on the sea floor. Shaanxilithes is a ribbon-shaped impression with constant widths (1-6 mm or more) and is characterized by a series of closely spaced transverse annulations. Shaanxilithes is tentatively interpreted as a sessile epibenthos, with one end anchoring to the sandy or muddy substrate. Therefore, the Gaojiashan biota is characterized by complex morphological types and diverse body plans of variable size and lifestyle, representing a major biological innovation in Earth’s evolution. Flourishing microbial mats on the Precambrian level-bottom forced the Gaojiashan biota to evolve some adaptive strategies, either through fixation to (such as Cloudina, Conotubus, and possibly Shaanxilithes) or free laying on (such as Gaojiashania and Sinotubilites) the substrate by adhering to or inserting into microbial mats. To cope with the frequent disturbance by storm events, ecological adaptations were manifested in many Gaojiashan organisms. The polygonal cross-section and longitudinal ridges in Sinotubulites may stabilize the tube lying on the substrate, preventing it from rolling in strong currents. After being subjected to sediment obrution, Cloudina and Conotubus employed specialised palaeoecological strategies to rejuvenate and self-right the tubes, while Gaojiashania and Sinotibulites could partially self-right through curving, extension and constriction, indicating strong burial-resistant capabilities. Abundant meandering traces and possible burrows in the Gaojiashan biota and in the comparable Shibanta biota imply that bilaterians were an essential part of later Ediacaran ecosystems and indicate the possible presence of epibenthic and semibenthic free-moving and detritus-feeding organisms. The complexity of predator-prey dynamics at the beginning of metazoan diversification is evidenced by borings on Cloudina tubes. Figures and Tables | References | Related Articles | Metrics

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Cambrian lobopodians: confusion and consideration OU Qiang 2020, 27(6): 47-66.  DOI: 10.13745/j.esf.sf.2020.6.21 Abstract ( 322 )   HTML ( 9 )   PDF (15001KB) ( 314 )   Marine lobopodians that boomed worldwide during the early Cambrian have been broadly considered as closely affiliated with living panarthropods, including onychophorans (velvet worms), tardigrades (water bears), and arthropods (insects, crustaceans, myriapods, chelicerates, and allies). Despite the great ecological gap, extant terrestrial onychophorans and tardigrades are widely considered as the surviving descendants of Cambrian marine lobopodians. Resemblances between early lobopodians and living onychophorans are not just caterpillar-like gross morphology but distinctive features, such as foremost the unjointed lobopodous limbs. Another lineage of early lobopodians is believed to have given birth to the earliest stem arthropods, forming the largest animal phylum on our planet today. This epic evolutionary story has attracted many scientists to speculate on their evolutionary scenarios and phylogenetic significance. However, conundrums around these enigmatic animals remain unsolved. Here, I tentatively propose some arguments against mainstream views and offer some hypothetical approaches to researches on Cambrian lobopodians. Figures and Tables | References | Related Articles | Metrics

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Evolutionary framework of early Cambrian cnidarians from South China HAN Jian, GUO Junfeng, OU Qiang, SONG Zuchen, LIU Ping, HAO Wenjing, SUN Jie, WANG Xing 2020, 27(6): 67-78.  DOI: 10.13745/j.esf.sf.2020.6.3 Abstract ( 332 )   HTML ( 3 )   PDF (6819KB) ( 255 )   Cnidarians were an important component of the paleomarine ecosystem in the early Cambrian period in South China. In this paper, the evolution of early Cambrian cnidarians was discussed primarily based on the fossil records from the Kuanchuanpu, Yanjiahe and Chengjiang biotas in the Yangtze Block. Most early Cambrian cnidarians predominantly belong to the Superclass Medusozoa. By contrast, those of the Class Anthozoa are scarce. All fossil cnidarians in the Cambrian Fortunian Stage of South China are of microscopic sedentary forms with a variety of body radiation symmetries and exoskeletons; most of them are direct developers. In Cambrian Stage 2, the sedentary cnidarians exhibited an enlarged body size with only biradial or tetraradial symmetrical pattern. The fossil record of swimming jellyfishes firstly appeared in Cambrian Stage 3, associated with less sedentary forms, thus representing the emergence of the crown-group medusae and first establishment of complex life cycle with alternation of generations like modern jelly fish. A set of key characteristics, such as the indirect development, nerve ring, thickening of mesoglea, coronal muscles, rhopalium, concaved oral disk, deep subumbrella, tetraradial symmetry and loss of exoskeleton, are closely correlated and subsequently contribute to the step-wise rise of naked, pelagic and predatory medusae in Cambrian Stage 3. The rise of the medusoid stage in the life cycle of medusozoans invented many adaptational advantages. In return, however, it may have subsequently triggered a variety of changes in polyp morphology, structure and function, e.g., the shortening of polypoid stage and the loss of gonads and sexual reproduction. Thus the polyps of medusozoans are substantially different from anthozoan polyps. During the early Cambrian, the body size of the cnidarians and most other co-occurring metazoans increased significantly, mediated probably by various environmental factors, especially increase of ocean oxygen concentration. In the background of Cambrian radiation, the diversity and richness of cnidarians peaked at the dawn of the Cambrian, and then declined in Cambrian Stages 2-3, suppressed likely by the stepwise rising of bilateral animals. Most sedentary cnidarians that flourished in the Fortunian Stage did not extend into Cambrian Stage 3. Therefore, the fossil record of cnidarians from South China indicated the Cambrian explosion is not merely an event of animal radiations as it had witnessed a series of biotic replacements and even extinction of higher taxa in cnidarians. Figures and Tables | References | Related Articles | Metrics

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The earliest phosphatic-shelled brachiopods from the carbonates of South China: their diversification, ontogeny and distribution ZHANG Zhiliang, CHEN Feiyang, ZHANG Zhifei 2020, 27(6): 79-103.  DOI: 10.13745/j.esf.sf.2020.6.4 Abstract ( 176 )   HTML ( 4 )   PDF (18765KB) ( 256 )   Brachiopoda, as a key phylum of lophotrochozoan animals, plays an important role in studying the biodiversification of benthic communities during the Cambrian evolutionary radiation. Eight genera and twelve species of brachiopods, with the exception of three indeterminate taxa, are revealed and recovered from the Cambrian Series 2 carbonate facies near the Ediacaran-Cambrian boundary in the Yangtze Platform. They represent one of the earliest assemblages or components of brachiopods from South China. Based on the brachiopod data, the shell morphology and textural structures of the earliest variety of brachiopod groups and their occurrences and dispersals are discussed here to explore the origin and biodiversification of phosphatic-shelled brachiopods. We then summarised the recent research advances on the development of Cambrian brachiopods known from the Xihaoping Member of the Dengying, Shuijingtuo, and Yu’anshan formations of the Yangtze Platform. Lines of studies demonstrated that the linguliform brachiopods achieved adaptive diversity in the ornamentation of metamorphic and mature shells and shell structures, and in the configuration of pedicle foramen during the Cambrian explosion. In addition, three ontogenetic stages, including the pedicle foramen formation stage, pedicle foramen enclosure stage, and intertrough increasing stage, are observed in Cambrian Epoch 2 acrotretides. Compared with the ontogenetic developmental processes in different genera and species of acrotretides, the post-metamorphic allometry of shell valves was recognized as it played an increasingly significant role in the morphological diversification of different acrotretide clades. Furthermore, our recent studies on the earliest ontogenetic characteristics, preserved in the metamorphic shells in the oldest known lingulides and acrotretides, demonstrated that metamorphosis of planktotrophic larva is plesiomorphic for all brachiopods while the living lingulids are modified to obtain secondary larva with direct development. Interestingly, separate and diachronous occurrences of the oldest known brachiopods in the Cambrian palaeocontinents implied that linguliform brachiopods probably originated in East Gondwana and South China during the early Cambrian Epoch 2 and achieved a cosmopolitan dispersal subsequently. More studies on the diversity, ontogeny and biostratigraphy of the earliest phosphatic-shelled brachiopods will help us improve our understanding of their origination and the evolutionary changes of different lineages to uncover the correlation of Cambrian strata in detail. Figures and Tables | References | Related Articles | Metrics

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Recent research progress on small shelly fossils from the Cambrian (Terreneuvian) Yanjiahe Formation in the Three Gorges area GUO Junfeng, QIANG Yaqin, HAN Jian, SONG Zuchen, WANG Wenzhe, ZHANG Zhifei 2020, 27(6): 104-115.  DOI: 10.13745/j.esf.sf.2020.6.5 Abstract ( 332 )   HTML ( 6 )   PDF (9388KB) ( 203 )   The sudden appearance of small shelly fossils near the Ediacaran-Cambrian boundary represents one of the most conspicuous biomineralization events. It witnessed the explosive radiation of metazoans and signals the formation of the Cambrian ecosystem reigned by animals, especially bilaterians. The Yanjiahe Formation in the Three Gorges area represents one of the most important Cambrian stratigraphic sequences bridging the chronostratigraphic units between the Fortunian and Cambrian Stage 2. Here we summarize the recent progresses on small shelly fossils, particularly mollusks and cnidarians, from the Yanjiahe Formation to provide an important paleontological basis for defining the base of Cambrian Stage 2 and for better understanding the evolution and ontogeny of molluscs and medusozoans in early Cambrian oceans. The co-occurrence of Watsonella crosbyi and Aldanella attleborensis, both as the candidate GSSP markers for defining the base of Cambrian Stage 2, is documented for the first time at the base of Member 5 of the Yanjiahe Formation and assigned the age of Member 5 (Age 2). Watsonella crosbyi and A.attleborensis are widely distributed among Cambrian palaeocontinents (e.g., South China, Mongolia, Siberia, Avalonia) and range from low to high paleolatitudes in carbonate facies. The stratigraphic range is restricted to Cambrian Stage 2, which further supports the FAD of either W.crosbyi or A.attleborensis as a candidate GSSP marker for defining the base of this unit. Moreover, a single pair of cardinal processes below the apex of W.crosbyi most likely provide muscle attachment sites. This trait provides desiderative new data on the shell musculature of W.crosbyi, which suggests that this species is an untorted helcionelloid mollusc with an endogastrically coiled shell. The new hexangulaconulariid Septuconularia yanjiaheensis has a laterally compressed and biradially symmetrical deriderm, exhibiting fourteen gently tapered faces, thus representing a most specialized hexangulaconulariid taxon. Longitudinally, the periderm consists of three regions that probably correspond, respectively, to an embryonic stage, a transient juvenile stage, and a long adult stage. Septuconularia yanjiaheensis may have been derived from six-faced Hexaconularia(Fortunian Stage), which is mostly like a morphologically intermediate taxon between Arthrochites and Septuconularia. The new olivooid Octapyrgites elongatus is similar to the genera Olivooides and Quadrapyrgites from the Cambrian Fortunian Stage; its periderm consists of a quadrate apical region and a strongly corrugated reversed pagoda-like adapical region bearing folded apertural lobes. However, O.elongatus exhibits eight V-shaped apertural lobes while Quadrapyrgites has twelve. In contrast to the radiation-induced abundant medusozoans with diverse symmetry patterns during the Fortunian Age, the paucity of olivooids and absence of pentaradial cnidarians and carinachitids in Cambrian Stage 2 indicate a marked decline in the disparity of cnidarians during the Fortunian-Age 2 transition, when, by contrast, bilaterians underwent rapid diversification. Figures and Tables | References | Related Articles | Metrics

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Dynamic response of Mesozoic-Cenozoic foraminiferal paleogeography to the Tibetan Tethys evolution WAN Xiaoqiao 2020, 27(6): 116-127.  DOI: 10.13745/j.esf.sf.2020.6.1 Abstract ( 214 )   HTML ( 5 )   PDF (3512KB) ( 216 )   Foraminiferal data are the critical record of geological history, they reflect the dynamic changes of geographic patterns and ecologic environments. Various scientific issues, like tectonic evolution and changes of relative positions of plates, are the research topics of geoscientists. Foraminiferal ecology and paleogeographic distribution studies can recognize the peleobiogeographic realms and trace the tectonic evolution. One result of such studies is the recognition that Mesozoic-Cenozoic paleobiogeographic differentiation in Tibet is a dynamic response to the Tibetan-Tethys evolution. In the Early Jurassic, larger benthic foraminifera Orbitopsella and bivalve Lithioties occurred in southern Tibet, both are thermophilic fauna living in the circum-Tethys shallow water. They were dominant during the Pliensbachian to early Toacian. In the Late Jurassic, psychrophilic Buchia biota emerged in southern Tibet. They are identical to the Buchia and Retroceramus found in the Antarctic, south end of South America, New Zealand and Australia. It implies that the opening of Neothetys, especially the Central Atlantic, pushed the Indian Continent southward from lower to higher latitudes. The foraminiferal fossils in the Lower Cretaceous are poorly preserved in Tibet. In the mid-Cretaceous, larger benthic foraminifera Orbitolina widely developed in the Lhasa and Qiangtang basins of the Asian Continent. It occurred frequently in the shallow marine belts surrounding the Tethys Ocean during the late Barremian to Cenomanian of the Cretaceous. Its distribution extends to Myanmar in the east and Ladakh to the west. Along the coast of Tethys, it migrated to Japan, Malaysia, Indonesia, Kashmir, Afghanistan, the Middle East, West and South Europe, North Africa and the Caribbean regions. However, it never migrated into the Indian continent where a mixed planktonic and smaller benthic foraminiferal fauna appeared during that time. Orbitolia was also found in the Tanganyika region in East Africa, but it did not migrate eastward into the Indian continent either. Like Orbitolina, a bivalve fauna of Isodomella-Caestocorbula was found in the Lhasa block, and no affinity to the Indian continent was recognized. The distributions of Orbitolina and related biotas provide the basis for the reconstruction of tectonic paleogeography. By the mid-Cretaceous, the Lhasa block had attached to the Eurasian continent. Along the Bangong Lake-Nujiang River Suture, the Tethys closed at the end of the Jurassic when the Lhasa block was located at the south margin of the Eurasian continent. The shallow water faunas like Orbitolina and bivalves could migrate along the east and west margins of the Eurasian continent. Paleobiogeographically, the Lhasa block belongs to the northern temperate realm in the Middle Cretaceous. The Indian continent started to move away from Africa by the early Cretaceous and drifted to the north. It was isolated from the Eurasian continent to the north and Africa to the west by the Neo-Tethys Ocean that was a barrier for migration of shallow water faunas. No Orbitolina has been found on the Indian continent where faunas are shown not to be closely related to the contemporary shallow water biota of the Eurasian continent. The migration of Orbitolina was obstructed by the Tethys Ocean, whereas the deep water environment was favorable to the thriving of planktonic foraminifera such as Ticinella-Rotalipora and Marginotruncana-Globotruncana faunas during the middle to late Cretaceous. Till the latest Cretaceous, deep sea existed between the Indian and Asian continents. There are fundamental differences in the biogeographical features of the two sides of the Yarlung Zangbo suture zone. Larger foraminiferal fauna of Orbitoides-Omphaloceclus lived along the northern margin of the Indian continent, whereas Lepidorbitoides-Pseudorbitoides fauna were restricted in the south margin of the Gangdisê magmatic arc. Stratigraphic and paleontological evidence documented the dramatic changes in themicrofauna content and sedimentary facies across the Cretaceous-Paleogene boundary. In the Gamba and Zhongba areas in southern Tibet, the boundary is marked by a major disconformity, separating platform carbonates from overlying terrigenous conglomerates and sandstones. Danian Rotalia-Smoutina-Lockhartia fauna was only found at the north margin of the Indian continent; it had disappeared from the Asian continent. The paleobiogeographic affinity was obscured by the terrigenous sandstones and boulder-size conglomerates in the Danian. After the Selandian (Paleocene), the biotic difference clearly ceased. Foraminifera Miscellanea-Daviesina fauna occurred similarly in between both sides of the suture. Therefore, supported by paleobiogeographic evidence, we argue that the initial collision of the Indian and Asian continental blocks should occur in the Danian time (~66-61 Ma). If that is the case, the major biotic and lithofacies changes at the Danian, observed in the Tibetan Tethys and mostly referred to as intrinsic to the eustatic sea level change, were likely driven by continental convergence of the Indian and Asian plates. In the Early Eocene, one common biogeographic realm was formed across both sides of the Yarlung Zangbo suture zone dominated by the Nummulites-Discocyclina fauna. Foraminiferal geography witnessed the initial collision between the Great Indian continental margin and the Asian continent in the Early Paleocene. Deep sea disappeared and a residual sea remained. The occurrence of Nummulites willcoxi-Globigerina ouachitaensis fauna indicates the uppermost marine sediments with a late Ecocene Priabonian age. Then, the Tethyan Himalaya closed and sea water retreated from southern Tibet during ~35-34 Ma. Figures and Tables | References | Related Articles | Metrics

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A PDO-like record documented by microfossils from the northern region of the California Current System since the Early Pleistocene SU Xin, CHEN Fang, YU Chonghan, GUO Ce 2020, 27(6): 128-143.  DOI: 10.13745/j.esf.sf.2020.6.23 Abstract ( 309 )   HTML ( 4 )   PDF (10301KB) ( 140 )   The California Current System (CCS) is a very important boundary current in the Northeast Pacific Ocean and it plays an important role in the global air-ocean interactions. On the interannual and decadal timescales, the ocean-climate change and activity of upwelling in the CCS are principally affected by the Pacific Decadal Oscillation (PDO, with variable periods ranging from 20 to 30 a). To understand the variation of upwelling activity in the northern region of the CCS since the Early Pleistocene and its main control mechanism, we analyzed the data of calcareous nannofossils (fossils of coccolithophores) and diatom fossils from the International Ocean Drilling Program Holes 1020B (southern site, at 41° N) and 1245B (northern site, at 44° N). Our results suggested that abundance variations in these two fossil groups were correlated with most glacial-interglacial cycles, by which high abundances of diatom fossils and nannofosills were associated with glacial and interglacial stages, respectively. Three ca.0.5 Ma long-term stages of fossil abundance variations were recognized: the Early Pleistocene Stage (1.5-1.1 Ma) featured by abundant nannofossils in both holes, the Middle Pleistocene Stage (1.1-0.65 Ma) by relatively abundant diatoms and nannofossils with opposite variation trends in the two holes, and the Late Pleistocene Stage (since 0.65 Ma) by relatively abundant diatoms with very low and sporadic nannofossils in Hole 1245B and contrarily, abundant nannofossils with less abundant diatoms in Hole 1020B. We proposed a mode of long-term dominance of “Pacific Decadal Oscillation (PDO-like)” in combination with “North Pacific Gyre Oscillation (NPGO-like)” mode to explain the possible mechanisms for these records. The northern region of the CCS had been affected by a long-term dominance of +PDO-like phase that led to decreased upwelling during the Early Pleistocene, and by an altering of -PDO (intensified upwelling ) and +PDO phases over the Middle Pleistocene Transition period (MPT). And for the last 0.65 Ma, the region was affected by an altering of strong -NPGO and weak -PDO phases for Hole 1020B, but only by -PDO phase for Hole 1245B. An abrupt increase in diatom abundance (by three times in Hole 1020B and five times in Hole 1245B) marked the setup of MPT at 1.1 Ma, and a significant change in abundances of calcareous nannofossils (3-fold increase and reduction at the southern and northern sites, respectively) indicated the end of MPT at 0.65 Ma. This altering of microfossil abundances was seen as the results of abrupt palaeoceanographic changes. It further implied that the shift from a positive to a negative phase of long-term PDO-like dominance period may be abrupt too. The opposite changing trends of these two fossil groups at the northern and southern sites during and after MPT indicated possible geographical differentiation of ocean-climate conditions in the northern region of the CCS. It provided the Pleistocene records for the study of modern air-ocean processes and biological distribution with the regional boundary at 40° N. Figures and Tables | References | Related Articles | Metrics

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A review on marine Cretaceous-Paleogene biostratigraphy of and major geological events in Tibet-Tethyan Himalaya LI Guobiao, WANG Tianyang, LI Xinfa, NIU Xiaolu, ZHANG Wenyuan, XIE Dan, LI Yuewei, YAO Youjia, LI Qi, MA Xuesong, LI Xingpeng, XIU Di, HAN Zichen, ZHAO Shengnan, HAN Yi, XUE Song, REN Rong, JIA Zhixia 2020, 27(6): 144-164.  DOI: 10.13745/j.esf.sf.2020.6.16 Abstract ( 405 )   HTML ( 6 )   PDF (13550KB) ( 393 )   The Cretaceous-Paleogene is an important geological period, during which a series of major geological events occurred, including oceanic anoxic events (OAEs), Cretaceous oceanic red beds (CORBs), large igneous provinces (LIPs), Cretaceous/Paleogene biota mass extinction, Paleocene-Eocene thermal maximum (PETM) as well as the collision between Indian and Asian plates, and the closing of the Neo-Tethys seaway. The study of these major geological events is helpful for gaining a better understanding of paleoceanography, paleogeography, and the paleoenvironment. Tracking and capturing these major geological events and reconstructing paleogeography requires the establishment of an accurate chronostratigraphic framework, for which paleontological study is an important tool. A set of well-preserved marine sedimentary sequences of the Cretaceous-Paleogene was discovered in southern Tibet, which well recorded the evolutionary processes of the Neo-Tethys and the India-Asia collision. Additionally, the evolutionary process of organisms during the major changes of geological environment can also provide evidence for the co-evolutionary relationships among climate, environment and biology during extreme environmental changes. In the past ten years, we conducted a systematic paleobiostratigraphic study of the Cretaceous-Paleogene marine strata in south Tibet, on which this paper reviews the research progress. Detailed biostratigraphic studies of two important global oceanic anoxic events, OAE 1d and OAE 2, were carried out in Gyangze, Gamba, and Zanda. Ninety-three species of 43 radiolarians were identified and they were divided into five radiolarian zones. The radiolarian fauna was significantly affected by OAE 1d at the Albian/Cenomanian boundary and OAE 2 at the Cenomanian/Turonian (C/T) boundary. Systematic studies of the Cretaceous foraminiferal biostratigraphy were carried out in Gamba and Zanda, from which 142 species from 65 foraminiferal genera were identified and they were divided into 19 planktonic foraminiferal zones. Biostratigraphic study of the foraminiferal showed that the Lengqingre Formation of the Qiangdong area in Gamba crosses the Cenomanian/Turonian boundary, marked by the first appearance of Helvetoglobotruncana praehelvetica. Global oceanic anoxic events, including a significant planktonic and benthic foraminiferal extinction event (OAE 2) occurred at the Cenomanian/Turonian boundary. When OAE 2 occurred, the dissolved oxygen content in the bottom waters significantly decreased, and the plankton-dwelling foraminifera Rotalipora in deeper waters gradually disappeared at the top of the R.cushmani Zone, while R.cushmani disappeared at the top of the R.cushmani Zone. After OAE 2, from the lower part of the H.helvetica Zone, fauna diversity and abundance began to increase. The foraminiferal extinctions found in southern Tibet closely resembled those found elsewhere in the world in time and scale, with plankton and many benthic species as the main victims. Recent research progress in 5 study areas are summarized below. (ⅰ) Progress in the biostratigraphic study of the Cretaceous ocean oxygen-rich events. The oceanic red beds are widely distributed in the global oceans throughout the Phanerozoic, mainly after the oceanic anoxic events. They represent typical oxygen-rich sediments and play an important role in marine scientific research. Over the past years, we have been continuously studying the micropaleontology of the CORBs including mainly foraminifers, radiolarians, and ostracods. The results showed that the ages of the CORBs in southern Tibet are of obvious diachroneity, which are the late Santonian to Campanian in Gyangze, the Campanian in western Sagya, the Maastrichtian farther west in Saga and Gyirong, the early Paleogene in Zanda in westernmost Tibet, the late Santonian to early/late(?) Maastrichtian in southern Kangmar, and the middle Campanian further south in Yadong. During the oceanic oxygen-rich period, organisms showed characteristics of extreme prosperity. (ⅱ) Progress in the K/Pg boundary biostratigraphic research. Based on the study of foraminifers from the Cretaceous-Paleogene marine strata in Xishan, Gamba, 112 species of 48 foraminiferal genera were identified, which included 65 species of 36 benthic foraminiferal genera and 47 species of 12 planktic foraminiferal genera, and 13 foraminifera zones in four sedimentary stages were recognized (TLK1-2, TP1-11). The results suggested: (1) An obvious foraminiferal extinction-recovery event occurred near the K/Pg boundary. The planktic foraminiferal Globotruncanca fauna and the larger benthic foraminiferal Lepidorbitoides, Omphalocyclus and Orbitoides, which once flourished in the Late Cretaceous, were almost extinct near the K/Pg boundary, and new foraminiferal fauna, represented by small benthic foraminifera such as Ranikothalia, Daviesina and Lockhartia, appeared in the early Paleogene. (2) The occurrence of larger benthic foraminifers, such as Alveolina, in East-Tethys was about 1 Ma later than in West-Tethys, supporting the hypothesis that benthic macroforaminifera migrated from west to east. (ⅲ) Progress in biostratigraphic studies of the PETM event. The benthic foraminifera biostratigraphic studies were carried out in the Paleogene Zongpu section of Gamba. Thirty-four species from 28 benthic foraminiferal genera were identified and they were divided into three foraminiferal assemblages. The results showed that the Paleocene/Eocene(P/E) boundary should be placed between the Zongpu and Zhepure Formations, marked by the extinction of two genera, Miscellanea and Operculina, below the P/E boundary, and by the emergence and prosperity of two genera, Alveolina and Nummulites, above the boundary. The benthic foraminifera in this section exhibited the evolutionary characteristics of extinction and recovery near the P/E boundary. The analysis of the carbon and oxygen isotope values near the P/E boundary showed that δ 13C negative drift occurred at the P/E boundary, with a minimum peak of -8.5‰, and its change curve was consistent with the global carbon stable isotope events during the same period. (ⅳ) Progress in the studies of the youngest marine deposits and the time of the disappearance of the Neo-Tethys. The final closure of the Neo-Tethys in Tibet meant that seawater was completely withdrawn from Tibet. Our study focused mainly on the biostratigraphic studies of the quantitative poly-phylum species in the youngest marine strata, which were commonly considered as possible locations of the youngest marine deposit in Tibet. Seventy-two species from 50 radiolarian genera were identified, and four radiolarian zones were recognized in the Sangdanlin and Beijia sections, Gyirong-Saga, representing the youngest marine deposit in Gyirong during the early Eocene. A total of 152 species of 35 planktic foraminiferal genera were identified and 11 zones were delineated. Categorization results also include: 42 species from 22 benthic foraminiferal genera and 3 assemblage zones; 57 species from 32 ostracod genera and 8 zones, 23 species from 14 calcareous nannofossil genera and 5 assemblage zones, 88 species from 63 dinoflagellate genera and 4 assemblage zones, 23 species from 18 palynological genera and 4 assemblages, 4 species from 4 charophytes genera, 29 species from 20 calcareous algae genera and 6 assemblages, and 11 species from 9 gastropod genera. These results indicated that the Neo-Tethys disappeared in the Yadong area after the late Eocene. Based on the above and previous research data, we speculate that the final closing of the Neo-Tethys in Tibet occurred after the late Eocene. Figures and Tables | References | Related Articles | Metrics

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The Cretaceous-Paleogene marine stratigraphic framework that records significant geological events in the western Tarim Basin XI Dangpeng, TANG Zihua, WANG Xuejiao, QIN Zuohuan, CAO Wenxin, JIANG Tian, WU Baoxu, LI Yuanhao, ZHANG Yingyue, JIANG Wenbin, KAMRAN Muhammad, FANG Xiaomin, WAN Xiaoqiao 2020, 27(6): 165-198.  DOI: 10.13745/j.esf.sf.2020.6.24 Abstract ( 496 )   HTML ( 12 )   PDF (21911KB) ( 525 )   The Cretaceous-Paleogene interval in the northeastern part of the eastern Tethys witnessed a large-scale transgression event that resulted in the formation of the trumpet-shaped bay in the western Tarim Basin. The Late Cretaceous to Eocene marine deposits in the western Tarim Basin record the evolutionary history of the eastern Tethys including a series of major climatic events, but studies so far lacked a comprehensive chronostratigraphic division and correlation framework achievable through detailed lithostratigraphic, biostratigraphic and stratigraphic investigations. In this study, we improved the stratigraphic division and correlation framework using the aforementioned approaches, and we also discussed a series of major geological events. The Cretaceous to Paleogene strata in the western Tarim Basin constitute the Kezilesu Group and the Kukbai, Wuyitake, Yigeziya, Tuyiluoke, Altashi, Qimgen, Gaijitage, Kalatar, Wulagen and Bashibulake Formations. These formations are rich in foraminifera, ostracods, calcareous nannofossils, dinoflagellates, spores and pollens, bivalves, and gastropods, and contain a few ammonites, brachiopods, sea urchins, and fish teeth. The western Tarim Basin has become an important site for studying climatic events, such as the Paleocene-Eocene Thermal Maximum (PETM). Based on the comprehensive biostratigraphic and chronostratigraphic studies, the age of the Kezilesu Group is recorded as Barremian-Albian and the ages of the Kukebai, Wuyitake and Yigeziya Formations as Cenomanian-Maastrichtian. The Tuyiluoke Formation is the transitional period of the Cretaceous-Paleogene, whereas the age of the Altashi Formation is early to middle Paleocene. The age of the Qimugen Formation is late Paleocene to early Eocene, and the ages of the Gaijitage, Kalatar, and Wulagen formations are early to middle Eocene. Finally, the Bashibulake Formation is of late Eocene in age. The Late Cretaceous to Eocene strata from the western Tarim Basin were biostratigraphically and chronostratigraphically correlated with those from the surrounding Kuqa, Fergana and Tajik Basins as well as the Karakoram region. Additionally, five large transgression-regression cycles from the late Cretaceous-Paleogene were summed. A possible small marine transgression of the western Tarim Basin began in the middle and upper parts of the Kezilesu Group (late Albian to early Aptian); however, the first large transgression began in the Cenomanian Kukebai Formation. There were five large-scale transgression-regression cycles in the western Tarim Basin from the late Cretaceous to Eocene. The seawater retreated from the Kunlun Mts. subregion of the western Tarim Basin at approximately 41 Ma and retreated from the Tianshan Mts. subregion of the western Tarim Basin at approximately 34 Ma. These transgression-regression events were controlled by regional tectonic events and global sea-level changes; however, the tectonic events mainly controlled the beginning and end of the Tethys Sea in the western Tarim Basin. The major climatic and geological events in the western Tarim Basin, such as OAE2, K/Pg, PETM, as well as transgression and regression, are discussed in detail. We successfully marked the PETM events in the Qimgen Formation, providing significant scientific clues for the study of PETM events in the global nearshore area. The western Tarim Basin should be further explored stratigraphically to establish a more refined biostratigraphic and chronostratigraphic framework to strengthen our study of major climatic and geological events in future. Figures and Tables | References | Related Articles | Metrics

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A review on Ordovician conodont biostratigraphy of the North China Plate and new research advances on its northwestern margin JING Xiuchun, ZHOU Hongrui, WANG Xunlian, YANG Zhihua, FANG Qiang, WANG Zhentao, FAN Jie 2020, 27(6): 199-212.  DOI: 10.13745/j.esf.sf.2020.6.8 Abstract ( 267 )   HTML ( 6 )   PDF (15477KB) ( 403 )   Conodonts are particularly important biostratigraphically for the subdivision and correlation of the carbonate-dominated Ordovician strata in North China. Studies of Ordovician conodonts from northern China have lasted for nearly half a century and can be distinguished into two stages. Researches in the first stage, from the 1970s to the beginning of the 21st century, were aimed to establish a basic conodont biostratigraphic framework for the paleontological dating and stratigraphic correlation of Ordovician strata in petroleum exploration. Studies in the second stage, from 2010-present, have been focused on the improvements and/or revisions of the conodont zonation established in the first stage in order to connect with international stratigraphic research. Investigations conducted recently on Ordovician conodonts from the northwestern margin of the North China Paleoplate suggested that three stratigraphic intervals with ecological differentiation can be recognized. The first ecologically-specific stratigraphic interval, which covers the middle Darriwilian, is characterized by the presence of conodont taxa inhabiting the marginal areas of tropical carbonate platforms between the North American midcontinent and North Atlantic ecoprovinces. The second interval, with a stratigraphic range spanning from the late Darrwilian to middle Sandbian, features conodonts mainly of North Atlantic affinity and associated with some Australasian species. The third interval, ranging from the late Sandbian to middle Katian, possesses conodont taxa with a mixture of Australasia and North American midcontinent affinities. For an easy and reliable international correlation, recent biostratigraphic studies on Ordovician strata on the northwestern margin of the North China Paleoplate have concentrated on using widespread conodonts as zonal indices, and an updated conodont biozonal succession comprising 12 biozones has been established. They are, in ascending order, (Darriwilian) the Histiodella cf. holodentata Interval Zone, Histiodella kristinae Phylozone, Histiodella bellburnensis Range Zone, Dzikodus tablepointensis Interval Zone, Eoplacognathus suecicus Interval Zone, Pygodus serra Interval Zone, Pygodus anserinus (early form) Interval Subzone, (Sandbian) Pygodus anserinus (late form) Interval Subzone, Belodina compressa Interval Zone, (Katian) Belodina confluens Interval Zone, Yaoxianognathus neimengguensis Interval Zone, and Yaoxianognathus yaoxianensis Interval Zone. However, correlations of some conodont biozones with their international namesakes are still somewhat controversial, hence additional biostratigraphical work remains to be done. Figures and Tables | References | Related Articles | Metrics

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Carboniferous foraminifers from the Shangsi area in southern Guizhou and the Visean foraminiferal succession in South China SHEN Yang, WANG Xunlian, LI Yukun, YANG Zhihua, CEN Wuxuan, WANG Xuebing 2020, 27(6): 213-233.  DOI: 10.13745/j.esf.sf.2020.6.18 Abstract ( 148 )   HTML ( 2 )   PDF (20950KB) ( 139 )   Abundant and highly diversified foraminifers were widely distributed in the Carboniferous period with high evolutionary rate, which is of great significance to the stratigraphic division and correlation. Compared with some important Carboniferous sedimentary regions in the world, the accuracy of the foraminiferal biostratigraphic division in South China is relatively low. We report in this paper on the abundant foraminifers from the Jiusi Formation and from the lower part of the Shangsi Formation, both are token as the representative lithostratigraphic units of the Carboniferous system in South China. Based on the existing data of foraminifers, seven foraminiferal zones are recognized in the Visean stage of South China. In ascending order, they are the Eoparastaffella simplex, Viseidiscus/Planoarchaediscus, Paraarchaediscus Zone, Pojarkovella nibelis, Koskinotextularia, Bradyina, and Janischewskina Zones. These foraminiferal zones can be well correlated with other typical Carboniferous sedimentary regions in the world, thus providing a high-resolution stratigraphic framework for related studies. Based on the study of foraminifers from the Shangsi area, we propose that the first appearance of foraminifer Bradyina can be used as a biostratigraphic criterion to define the base of the Shangsian Stage, a regional chronostratigraphic unit of the Carboniferous system in China. Moreover, the Shangsian Stage can be correlated to the middle and upper parts of the Warnantian Substage in Western Europe or to the Aleksinian-Venevian Substage in Russia. Altogether it provides reliable fossil evidence for the regional chronostratigraphic unit correlation of the Carboniferous system worldwide. Figures and Tables | References | Related Articles | Metrics

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Intraspecies variation and biostratigraphic correlation in charophyte population LI Sha, WANG Qifei, ZHANG Haichun, WAN Xiaoqiao 2020, 27(6): 234-240.  DOI: 10.13745/j.esf.sf.2020.6.10 Abstract ( 179 )   HTML ( 2 )   PDF (18319KB) ( 86 )   Traditional charophyte fossil studies indicated that these fossils played a significant role in the stratigraphic division of the Cretaceous/Paleocene boundary. However, the continental correlation of charophyte species is hard to carry out due to lack of a united taxonomy standard. According to previous studies on modern charophytes, the spiral cells of gyrogonites in one species showed changes from concave to convex due to different degrees of calcification. Therefore, the identification of charophyte fossil taxa based on populations was introduced. Gyrogonite polymorphism is often found in the population of one of the species. If the changes in characteristics are transitional, these different morphologies are called intraspecific variations. Studies of intraspecific variations could provide evidence for species determination and further biostratigraphic correlation between Chinese and international charophyte populations. Palaeoecology and palaeogeography are also important for studying charophyte biostratigraphy. Eurytopic and widely distributed species can be used to denominate biozones, which are beneficial to intercontinental stratigraphic correlation. Figures and Tables | References | Related Articles | Metrics

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High-resolution spatial distributions of diatoms in surface sediments and their correlations with environmental factors in the central and northern South China Sea LI Shun, WU Cong, CHEN Chixin, JING Xia, LI Xuejie, CAI Guanqiang, ZHONG Hexian, ZHANG Jiangyong, LI Bo, ZHANG Jinpeng 2020, 27(6): 241-254.  DOI: 10.13745/j.esf.sf.2020.6.11 Abstract ( 224 )   HTML ( 6 )   PDF (13116KB) ( 165 )   To map the present distribution of sedimentary diatoms, a new data set on the relative abundance of diatom species preserved in 1266 surface sediment samples is generated, which covers the environmental factor characteristic of the central and northern parts of South China Sea (SCS) between 12° and 24°N. The biogeographic distribution patterns of as well as the preferences for environmental variables for 19 diatom species are documented. The relative abundance patterns of the major diatom species were statistically compared with six environmental variables, namely the annual sea surface temperature and salinity, dissolved oxygen, and concentrations of three surface nutrients (nitrate, phosphate, silicate). Pearson correlation and redundancy analyses indicated that species correlated so strongly with the environmental factors that six diatom assemblages could be established. Among which, the Paralia sulcata-Actinoptychus undulatus and Cyclotella stylorum-Cyclotella striata-Actinoptychus splendens-Coscinodiscus decrescens assemblages, located on the east and west sides of the Pearl River Estuary on the northern continental shelf of the SCS, respectively, are related to freshwater inputs from the Pearl River and Guangdong coastal current and Kuroshio intrusion. The Cyclotella striata-Paralia sulcate assemblage off the coast of Vietnam is related to the western boundary current of the SCS. The Nitzschia marina-Rhizosolenia bergonii-Azpeitia africana-Chaetoceros messanensis-Fragilariopsis doliolus assemblage in the northeastern SCS is significantly influenced by the Kuroshio intrusion and the SCS warm current and northern slope current. The Azpeitia nodulifera-Nitzschia marina-Hemidiscus cuneiformis and Azpeitia nodulifera-Nitzschia marina-Thalassionema nitzschioides-Cyclotella striata assemblages located on the Xisha Islands and in the SCS deep-water basin, respectively, correlate strongly with the sea surface temperature pattern. Some biological and sedimentological factors may cause stronger effects on diatom distribution, and may mask the influences of environmental variables. Figures and Tables | References | Related Articles | Metrics

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Deep sea benthic foraminifera from the Taixinan Basin and changes of their cold seep microhabitats during the past 50000 years SU Xin, QU Ying, CHEN Fang, YANG Shengxiong, ZHOU Yang, CUI Hongpeng, YU Chonghan, TENG Tiantian 2020, 27(6): 255-275.  DOI: 10.13745/j.esf.sf.2020.6.13 Abstract ( 249 )   HTML ( 3 )   PDF (7515KB) ( 159 )   Benthic foraminifera and their shell oxygen and carbon isotopes from Core 973-4, located on the slope of the Jiulong Methane Reefs cold seep area, and Core 973-5 on the edge of the Haiyang No.4 Site in the Taixinan Basin, were studied to understand the characteristics of fauna assemblages, their ecological factors, and the change in microhabitats with time. The ages of sediments from the two cores were determined to be 50 ka, which were assigned to the late Pleistocene Marine Oxygen Isotope Stage MIS 3 to early MIS 1. In total, 233 species of 79 genera were identified for the benthic faunas from the two cores. The dominant taxa from Core 973-4 were Uvigerina (23.3%),Bulimina (10.71%) and Cibicidoides (9.87%), while from Core 973-5 was Bulimina (20.6%). Generally, these two faunas were dominated by infauna taxa. Foraminiferal diversity was influenced by TOC and sediment grain sizes. A weak correlation between dominant (or common) taxa with TOC and varying degree of correlation with δ18OUvigerina spp. indicated that foraminifera taxa were also affected by other special nutrition and fluids in the cold seep areas. Over the last 50 ka, the microhabitats of benthic foraminiferal assemblages from Cores 973-4 and 973-5 changed from bivalve shell debris-authigenic carbonates (MIS 3 to early MIS 2) to bivalve-bacterial mats (late MIS 2 to early MIS 1). Correspondingly, from MIS 3 to MIS 1, the dominant taxa of foraminiferal assemblages from Core 973-4 changed from U.peregrina to Cibicidoides-Bulimina then to U.vadescens-Cibicides and from Core 973-5 changed from Chilostomella+Globobulimina to Cibicidoides then to Bulimina. Oxygen and carbon isotopic profiles of foraminiferal shells also changed with time, showing enriched δ18O (3.5‰-4.49‰) and depleted δ13C(-2.0‰ to -0.2‰), as results of exchanging ambient pore fluids with authigenic carbonates during the period of MIS 3 to early MIS 2 and biogeochemical processes in the microhabitats of bivalve and bacterial mats during the time of late MIS 2 to early MIS 1. Generally, the activity of methane seeping decreased gradually during the past 50 ka in these two cold seep regions. Several enhanced seeping events during this period were indicated by abnormal δ18O and δ 13C values. One persistently enhanced seeping event, lasted about 10 kyr (35-25 ka), was seen in Core 973-4. In Core 973-5, three short events (at 45 ka, 35 ka, and 14-12 ka) were found, among them the 45 ka event may be the strongest one as methane flux reached near the surface of the sea floor to form gas hydrates near the seafloor, where as the 35 ka event was inferred as a regional one. Figures and Tables | References | Related Articles | Metrics

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Distribution of benthic foraminiferal taphocoenose in surface sediments and the environmental implication in the radial sand ridge of the South Yellow Sea YUAN Jieqiong, DING Xuan, ZOU Xinqing 2020, 27(6): 276-288.  DOI: 10.13745/j.esf.sf.2020.6.20 Abstract ( 147 )   HTML ( 0 )   PDF (11211KB) ( 121 )   We analyzed a total of 123 surface sediment samples obtained from the radial sand ridges (RSR) to uncover the relationships between the marine environmental parameters and foraminiferal assemblages. The results showed that the percentage of planktonic foraminifera was less than 7%, and its distribution was related to the offshore tide. The study area was dominated by foraminiferal species with high tolerance to shallow water and low salinity. Fifty-nine species with percentage contents ≥2% in more than three samples were chosen for the Q-mode factor analysis, from which three maximum variance (varimax) factors were obtained. By combining sediment particle size and modern marine environmental parameters, the study area was divided into three environmental zones: (1) The central RSR and large tidal inlet correspond to an Ammonia beccarii vars.-Nonion akitaense-Cribrononion frigidum assemblage. This area can be divided into two subregions: the northern RSR and large tidal inlet region representing the strong hydrodynamic nearshore sandy sedimentary environment affected by low-temperature coastal currents and tidal currents, and the southern study area including the Yangtze River Estuary reflecting the estuarine environment affected by strong oceanic tidal current. (2) The Haizhou Bay and the abandoned Yellow River Estuary region relate to the Ammonia compressiuscula-Spiroloculina laevigata-Elphidium advenum assemblage, representing a shallow sea environment (50 m) with silty sand and clay-based sediments. (3) The shallowest coastal areas of the southern RSR correspond to the Nonion anomalinoidea-Ammonia maruhasii-Ammonia pauciloculata assemblage, signifying the environment of nearshore shallow water, a low-salinity intertidal zone, or a subtidal zone with a silty and sandy bottom impacted by strong hydrodynamic force. In general, the distribution of benthic foraminiferal assemblages from the RSR is not only affected by temperature and salinity, but also related to the unique hydrodynamic condition, which is affected by offshore tidal current and inland rivers. Figures and Tables | References | Related Articles | Metrics

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Rapid response of diatom biodiversity to millennial-scale abrupt change of climate: a case study of the last glacial record of the Yunlong Lake, Yunnan Province LUO Hai, LI Jie, ZOU Yafei, XU Huiming 2020, 27(6): 289-299.  DOI: 10.13745/j.esf.sf.2020.6.22 Abstract ( 189 )   HTML ( 5 )   PDF (8182KB) ( 118 )   Lakes are an important component of the global ecosystems. Although biodiversity plays a very important role in lake’s primary productivity and lake ecosystems, little is known about how it responded to climate change on the millennial timescale most relevant for predicting future changes. Diatoms are one of the important primary producers in lakes and their siliceous valves can be stably preserved in lake sediments for a long time, so they are an excellent indicator for the study of lake biodiversity changes in geologic times. In this study, we use diatom records from a 10.63 m comprehensive core obtained in the Yunlong Lake, southwest monsoon region of China to reveal the response of the lake biodiversity to the rapid climate change on the millennium timescale. The final age of the core was determined by Accelerator Mass Spectrometry (AMS)14C dating and Bacon age-depth modelling. Combining with diatom assemblage and α-diversity analysis, the evolutionary history of diatom diversity in the last deglaciation (569-1 063 cm, 19~10 calkyr B.P.) of the lake was constructed. The diatom assemblage and diatom diversity changes in the Yunlong Lake during the last glaciation can be divided into six intervals, including the late Last Glacial Maximum (LGM), the Early Last Deglaciation (E-LD), Herinrich 1 (H1), Bolling/Allerod (B/A), Younger Dryas (YD), and the Early Holocene (E-Holo). The variation of diatom diversity was generally high during warm periods (E-LD, B/A) and low during cold periods (LGM, H1, YD). At the same time, with the rapid change of global temperature, diatom diversity also responded rapidly: it increased rapidly when temperature turned warm (B/A warm period) and decreased rapidly when temperature turned cold (H1 and YD). These changes were mainly related to the changes of lake environmental conditions (such as the length of ice-cover period and the changes of aquatic vegetation in littoral zone, etc.) driven by temperature changes. Our results show that during the last deglaciation period, diatom biodiversity responded quickly to the millennium-scale abrupt climate events and synchronized with rapid climate fluctuations; on a long timescale, climate warming may be beneficial to the maintenance of biodiversity of alpine lakes. Figures and Tables | References | Related Articles | Metrics

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Spatial distribution characteristics of radiolarian species in surface sediments from the Okinawa Trough and the impact of environmental factors DONG Zhi, SHI Xuefa, ZOU Xinqing, ZOU Jianjun, YANG Baoju, LIU Jihua, CHENG Zhenbo 2020, 27(6): 300-312.  DOI: 10.13745/j.esf.sf.2020.6.9 Abstract ( 158 )   HTML ( 1 )   PDF (5476KB) ( 93 )   We systematically analyzed the newly collected radiolarian assemblages data from 34 surface sediment samples that span the northern, middle and southern Okinawa Trough to better understand the regional species compositions and distribution range. Our study provided the first detailed regional characterization on the modern distribution patterns of radiolarian species under varying temperature, nutrient, and water depth. The results showed that diverse subtropical species dominated the radiolarian assemblages in all samples.The most abundant species was Tetrapyle octacantha Müller group (23%), followed by Spongodiscus resurgens and Euchitonia furcata. Variation in the radiolarian assemblages in different parts of the Okinawa Trough could reflect the differences in the overlying water masses. In general, the relative abundance of warm-water species decreased with increasing latitude. However,the distribution pattern of the T.octacantha group showed an opposite trend with high abundance in the western continental slope of the northern Okinawa Trough. The northern Okinawa Trough near the East China Sea continental shelf is strongly affected by the Changjiang diluted water,resulting in large seasonal variations of temperature and salinity. The T.octacantha group has been found to have stronger tolerance to relatively lower temperature and thus is able to become the dominant species in the northern Okinawa Trough. In this study,the depth-related distribution of radiolarians in the Okinawa Trough was also investigated. The lower abundances of Cycladophora davisiana and Actinomma leptodermum, which are the mid-water species in the Okinawa Trough,may be partly related to the impact of higher mid-water temperature. Another factor that may affect the distribution pattern of deep-water dwellers in the Okinawa Trough is the inhibition effect of shallow straits on the Pacific deep water intrusion. Figures and Tables | References | Related Articles | Metrics

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Artinskian (Early Permian) marine environmental disparity and evolved fusulinid foranminifa in the Dianqiangui Basin, South China HUANG Mingli, TIAN Kunxuan, SHI Yukun 2020, 27(6): 313-328.  DOI: 10.13745/j.esf.sf.2020.6.12 Abstract ( 225 )   HTML ( 6 )   PDF (6471KB) ( 174 )   During the Artinskian age of the Early Permian, the marine environment was diverse in the Yunnan-Guizhou-Guangxi junction area, namely the Dianqiangui Basin, in South China, where restricted or semi-restricted marine lagoon and open and marginal marine platforms have been recognized and distinct fusulinid fauna evolved. The current study is designed to pursue the relationships among different marine environments and fusulinids. Two carbonate sections, the Dawang and Zhuzichong Sections in southern Guizhou, were studied in detail and described here for their Asselian to Artinskian strata. The Artinskian strata of the Dawang Section are mainly composed of sparite bioclastic and microcrystalline bioclastic limestones, indicating an open or marginal marine platform environment. Eighty-two fusulinid species belonging to 19 genera are recovered there, and four fusulinid biostratigraphic zones are recognized, including, in ascending order, the Pseudoschwagerina beedei-Sphaeroschwagerina constans concurrent range zone, the Staffella xiushuiensis-Eoparafusulina contracta abundance zone, the Pseudofusulina ellipsoidalis abundance zone, and the Misellina subcycloidea interval zone. In the Zhuzichong Section, calcareous mudstones were deposited during the Artinskian, suggesting a restricted or semi-restricted marine lagoon environment. Sixty-two fusulinid species belonging to 14 genera are found there and three fusulinid zones have been defined, ascendingly: the Pseudoschwagerina uddeni-Sphaeroschwagerina sphaerica assemblage zone, the Eoparafusulina certa abundance zone, and the Staffella discoides range zone. Moreover, another section of this area, the Zongdi Section, was introduced for its Artinskian strata, as well as the Staffella-Pseudoendothyra assemblage zone recognized there. An extended cross-sectional study, covering sections featuring different types of marine environments in the Dianqiangui Basin, revealed the characteristics of fusulinid fauna that evolved there. During the Artinskian, Pamirina was the typical genus in the open or marginal marine platform along with thriving schwagerines, while staffellines developed abundantly in the restricted or semi-restricted environment. The main marine environmental factors affecting the fusulinid foraminifera included hydrodynamics and sunlight and oxygen, which could explain the fusulinid distributions in different marine environments. Fusulinids developed large fusiform tests and strong septa flutes, such as schwagerines, with small test surface-to-volume ratios, therefore are more suited for the open and marginal platform environments with strong waves, good sunlight, and sufficient oxygen. However, staffellines have small lenticular tests and simple inner structures with large test surface-to-volume ratios, which enabled their survival in restricted environments with less sunlight and low oxygen. Figures and Tables | References | Related Articles | Metrics

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Microvertebrate remains from the Kuanti Formation of the Liujiachong Section in Qujing, Yunnan and their stratigraphic significance WANG Jianhua, ZHAO Wenjin, ZHU Min, LI Qiang, CAI Jiachen, ZHANG Na, PENG Lijian, LUO Yanchao 2020, 27(6): 329-340.  DOI: 10.13745/j.esf.sf.2020.6.7 Abstract ( 292 )   HTML ( 5 )   PDF (4534KB) ( 239 )   The Kuanti Formation, with the discovery of the Xiaoxiang Vertebate Fauna in 2007, has become the focus of global research on early vertebrates. However, its stratigraphic subdivision, correlation and age, especially the subdivision and age of its lower part, remain contentious, despite many biostratigraphic attempts made since 1914. In recent years, we conducted a series of extensive geological investigations in the Kuanti Formation near the Xiaoxiang Reservoir in Qujing, Yunnan Province. Based on the recently obtained data from the Liujiachong Section (dominated by the lower part of the Kuanti Formation) and the preliminary study of the newly discovered microvertebrate remains, we documented the sequence of the Kuanti Formation of the Liujiachong Section, and further explored the geological age of the related strata. The Kuanti Formation of the Liujiachong Section can be subdivided into three members, in ascending order according to the main lithological changes: Member Ⅰ (Yuejiashan Member), Member Ⅱ (Chongjiawan Member), and Member Ⅲ (Cailian Member). The lower part of Member Ⅰ is characterized by light yellow and yellow-green gravelly silty mudstones and calcareous siltstones lacking any fossils, while the upper part is composed of dark grey and grey-black carbonaceous shales with rare Lingula sp. and bivalves. Member Ⅱ is dominated by grey-green and purple-red shales, intercalated with light grey thin-bedded or lenticular limestones or bioclastic limestones containing many invertebrate fossils (brachiopods and crinoid stems) and abundant microvertebrate remains. Member Ⅲ, partially exposed in the section, is composed of purple-red and grey-green silty and calcareous mudstones or marls intercalating with minor purple-red or yellow-green shales or siltstones containing brachiopods, fish, and stout tubular trace fossils. A thin layer of medium-thick-bedded fine sandstone is developed on the bottom of the member, which marks the boundary between Members Ⅲ and Ⅱ. The microvertebrate remains from several beds in Member Ⅱ show high diversity, including four early vertebrate groups: agnathans, placoderms, acanthodians, and osteichthyans. They are characterized by the Yangtze Fish Assemblage of the Xiaoxiang Vertebrate Fauna. The discovery of the acanthodians Nostolepis spp. in this section reveals the stratigraphic correlation and the precise geological age of the lower part of the Kuanti Formation. Based on the acanthodians from Member Ⅱ, coupled with previous palaeontological data, we suggest the age of Member Ⅱ to be late Gorstian Stage of the Ludlow, in the Silurian. The upper part of Member I, containing the placoderm ‘Wangolepis’, might be referred to as early Gorstian. However, the age of the lower part of Member I without fossils is uncertain, and the possibility of its base extending down to the Wenlock is not excluded. This study offers new palaeoichthyological evidence for the Silurian biostratigraphy of China and provides a new chronostratigraphic scheme in the study of early vertebrate evolution. Figures and Tables | References | Related Articles | Metrics

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The Late Ordovician fish-like animal from Xinjiang GUO Xianpu, WANG Shitao, GAI Zhikun, ZHAO Ziran, DING Xiaozhong, LI Tianfu 2020, 27(6): 341-346.  DOI: 10.13745/j.esf.sf.2020.6.17 Abstract ( 297 )   HTML ( 4 )   PDF (10956KB) ( 189 )   This paper is the first to report the discovery of a well-preserved Ordovician fish-like animal fossil with a reliable shield armor structure. The vertebrate fossil was collected from purplish-red sandy-limestone outcrops of coast-shallow marine facies that are part of the Upper Ordovician Qarbake Formation in the Yijianfang section, Bachu county, Xinjiang. The new genus and species has been denoted Haoina elegantia Guo & Wang as per the system of binomial nomenclature, and a new family (Haoinaspididae) and order (Haoinaspidiformes) have also been described based on the unique biological features of this species. The new genus describes an ostraeoderm, while the Qarbake Formation can be constrained to the Sandbian stage based on the conodont fossil zone. The fossil of the new fish-like animal preserves its dorsal shield armor and shows that the dorsal shield on its head is covered with ridges composed of complex tumors on the derma. The ridges can be subdivided into four types: The orbit openings are situated at the dorsal-front edge of the head shield with wide and deep orbit hollows. The pineal area is located at either side of the orbits. And the well-developed sensory canal system in the armor of the head shield shows the tube system texture of corium and subcutaneous tissues. Based on comparisons with the vertebrate biogeographic regions of other fossils, we suggest the establishment of a new fish-like animal typified in a proto-Tethys Ordovician Haoniaspid-Bachuiaspid vertebrate biogeographic province. This fossil is the oldest fish-like animal with a reliable exoskeleton found in China or even in Asia. Figures and Tables | References | Related Articles | Metrics

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Comparison of biodiversity of the Early Cretaceous pterosaur faunas of China WANG Xiaolin, LI Yang, QIU Rui, JIANG Shunxing, ZHANG Xinjun, CHEN He, WANG Junxia, CHENG Xin 2020, 27(6): 347-364.  DOI: 10.13745/j.esf.sf.2020.6.19 Abstract ( 440 )   HTML ( 9 )   PDF (24877KB) ( 330 )   A large number of continental basins in northeastern and northwestern China contain abundant vertebrate fossils in lacustrine deposits. Among them, the Wuerho Pterosaur Fauna from the Junggar Basin on the north side of the Tian Shan Mountains, the Hami Pterosaur Fauna from the Turpan-Hami Basin on the south side of the Tian Shan Mountains, and the Jehol Biota of western Liaoning, all bear rich pterosaur fossils. The former two faunas of northwestern China shared similar prosperous time and were both discovered in the Lower Cretaceous Tugulu Group. Pterosaur diversity of these two faunas is low but the faunas included abundant individuals. Fossils of the Wuerho Pterosaur Fauna, preserved mostly in the fine-sandstones and siltstones of the semi-deep lacustrine deposits, were relatively complete and formed by normal death. The fossils of the Hami Pterosaur Fauna were largely preserved in the tempestites of the event deposits of a shore-shallow lake. The disarticulated bones were complete after the short-distance transport by storms and a fast burial. By contrast, the pterosaurs of the Jehol Biota of northeastern China have high diversity as well as an association with fishes, amphibians, dinosaurs and other reptiles, and birdsand mammals, They were mainly preserved in the semi-deep to deep lacustrine shales. The skeletons are relatively complete, as a volcanic eruption caused massive death and fast burial (by volcanic ashes) creating a very different outlook from that of the two northwestern faunas. Based on the preliminary comparison of the pterosaur faunas from the south and north sides of the Tian Shan Mountains, we inter that the dominant pterosaurs on the north side, dsungaripterids, are distributed in the Junggar Basin and neighboring western Mongolia, that they have a distant relationship with the only known taxon, Hamipterus, from the faunas from the south side. Hence, we have proposed that the Tian Shan Mountains rose to a relatively high level in the Mesozoic, blocking the migration of the faunas from both sides of the mountains. In western Liaoning and its neighboring regions, the destruction of the North China Craton caused abundant volcanic eruptions, which created a highly diversified ecological environment with rapid replacements of creatures thus resulting in unique biodiversity in the Jehol Biota. However, the continental basins in northwestern China, which experienced no volcanic eruption, have low diversity but high abundancy of pterosaurs. Therefore, we proposed that the frequent and intense volcanic eruptions caused by the destruction of the North China Craton played an essential role in the varying diversity between the pterosaur faunas of northeastern and northwestern China. Figures and Tables | References | Related Articles | Metrics

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A new Early Cretaceous pterosaur from the Ordos region, Inner Mongolia JI Shu’an, ZHANG Lifu 2020, 27(6): 365-370.  DOI: 10.13745/j.esf.sf.2020.6.14 Abstract ( 679 )   HTML ( 1 )   PDF (4202KB) ( 355 )   The western Ordos region in Inner Mongolia, including Hanggin Banner and Otog Banner, is one of the most important localities yielding the Early Cretaceous Psittacosaurus Fauna across northern China. No pterosaur material had been formally depicted until Ordosipterus planignathus was named and described in the early 2020. Here, we report a new partial pterosaur mandibular symphysis discovered at the Zhaoshao site in the Luohandong Formation in Otog Banner. Its mandibular symphysis is long and straight and bears a developed lateral ridge that divided the dentary lateral side into the upper and lower parts. Nearly round dentary alveoli of each side lie just above the lateral ridge along a straight line anteroposteriorly. The diameters of alveoli (2-2.5 mm) vary slightly from rostral to caudal. The distance between the adjacent alveoli is about half the diameter of either alveolus. The tooth density is 3 teeth per centimeter. This pterosaur could be assigned to the family Ctenochasmatidae, it represents a new taxon-Otogopterus haoae gen.et sp.nov. The generic name refers to the type locality (Otog Banner) of this pterosaur, and the species name is in honour of Prof. Hao Yichun, who made outstanding contributions on the Mesozoic paleontology and stratigraphy in China. This new fossil is the second definitive pterosaur kind in the Inner Mongolian Ordos region following Ordosipterus planignathus, further enriching the components of the Early Cretaceous vertebrate fauna in this region. This pterosaur is also the second ctenochasmatid taxon in the Ordos Basin, after Huanhepterus quingyangensis from eastern Gansu Province. The new finding enlarged the geographical distribution of ctenochasmatid pterosaurs in the Ordos Basin and revealed the Ordos Basin to be another important distribution area of Ctenochasmatidae in China. Figures and Tables | References | Related Articles | Metrics

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Redescription of Eochondrosteus sinensis (Acipenseriformes, Actinopterygii) and its geological age LU Liwu, TAN Kai, WANG Xi 2020, 27(6): 371-381.  DOI: 10.13745/j.esf.sf.2020.6.6 Abstract ( 556 )   HTML ( 17 )   PDF (6392KB) ( 279 )   Acipenseriformes are a group of early actinopterygian fish with an unfossified vertebral column, a smooth body without scales, or only with a few rows of bone scute. The group comprises of four families, two of them have living members. They are Acipenseridae and Polydontidae, which include the living fish Acipenser and Psephurus from Asia, Polydon from North America, and some fossil species such as the Early Cretaceous Protopsephurus and Late Cretaceous Paleopsephurus. The other two families are only fossil species, they are Chondrosteidae found in the Early Lias of Europe, and Peipiaosteidae from the Middle Jurassic-Early Cretaceous of Northeast Asia. Eochondrosteus sinensis Lu, Li et Yang, 2005, which does not belong to any of the aforementioned families, was preserved in 2005 as the oldest fossil acipenseriform fish. It was found in a black-grey silty shale previously identified as Late Permian in age, exposed 50 km west of Mazongshan Township, Gansu Province, Northwest China. Based on certain newly prepared specimens, this fish is redescribed herein. The revised diagnosis is as follows: small-sized acipenseriform fish; vertebral column unossified but with a row of basal dorsal and supraneural along its body; frontal (fr) rectangular in shape, nearly the size of the parietal (pa); posttemporal (pt) large, triangular in shape; dermosphenotic (dsp) small, connected with infraorbital (io); subopercular (sop) fan-shaped with an elongated anterior process, large in size, nearly double that of the opercular (op); more than two branchiostegal rays and one large size gular plate present; upper jaw (max) uprise in its middle part and a triangular premaxilla (pmx) with sharp teeth in its anterior ventral edge; dentary (den) long and slim, toothed in the anterior part; dorsal fin located behind pelvic fin, and caudal fin heterocercal, with both dorsal and ventral fulcra scales present; and fish body smooth and scaleless, with only a few rhombic scales present in the upper lobe of caudal fin. Eochondrosteus can be distinguished from other acipenseriform fish by the following composed characteristics: (1) a large subopercular, with an elongated anterior extension; (2) a premaxillary bone present and a toothed jaw; (3) a large gular bone; and (4) a smooth body, with scales present only in the upper lobe of caudal fin. A brief phylogenetic analysis was performed mainly based on the character matrix of Hilton and Forey with a few modifications, and a heuristic tree search was conducted using the TNT(V1.5) software. The parsimony cladograms obtained show that Eochondrosteus is on the root of the phylogenetic tree, as the sister group of all other acipenseriformes. The result suggests that it could be the most primitive acipenseriformes fish, although some bone characteristics of the fish skull still need to be added. The opinion on geological age from recent studies on non-mammalian fossil reptiles (trirachodontid Beishanodon youngi) and on fossil fish (Plesiofuro mingshuica and scanilepiform Beishanichthyes) from the ‘Beishan Hills’ of Gansu, is temporarily agreed here. All relevant studies suggest an Early Triassic age for the fossil-bearing beds. Therefore, the age of Eochondrosteus sinensis was changed from Late Permian, dated in 2005, to Early Triassic as those ‘Beishan Hills’ fossils are regarded as having the same stratigraphic horizon and even the same fossil locality as Eochondrosteus sinensis, according to the literature review and field investigation. Eochondrosteus sinensis remains as the oldest acipenseriform fish. Figures and Tables | References | Related Articles | Metrics

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Core value of the Chengjiang fauna: formation of the animal kingdom and the birth of basic human organs SHU Degan, HAN Jian 2020, 27(6): 382-412.  DOI: 10.13745/j.esf.sf.2020.10.28 Abstract ( 1009 )   HTML ( 852 )   PDF (25271KB) ( 342 )   Figures and Tables | References | Supplementary Material | Related Articles | Metrics