Spiders are one of nature’s success stories, with spider webs distributed in nearly every corner of the world. Recently, the discoveries from the ca. 100 million year old Burmese amber of Myanmar shed important light on where spiders may have evolved from.
Spiders are one of nature’s success stories, with spider webs distributed in nearly every corner of the world. Recently, the discoveries from the ca. 100 million year old Burmese amber of Myanmar shed important light on where spiders may have evolved from.
Photo of Chimerarachne yingi gen. et sp. nov. Image by WANG Bo Chimerarachne is an extraordinary fossil spider from Burmese amber, described by an international research team led by Prof. WANG Bo from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), with the name comes from the way in which the new fossil seems to combine features of different arachnids, and is based on the chimera: a monster in Greek mythology composed of different animal parts. These “Monster Spiders” are with tiny sizes, less than 2 mm long (excluding tail). The body can be divided into prosoma and abdomen, with six eyes are medially located near the anterior margin of the carapace. Their appendages are similar to those of modern spiders, including a pair of chelicerae, pedipalps, and 4 pairs of legs. The fossils have four pairs of spinnerets, with anterior lateral and posterior lateral spinnerets bearing 14 and 12 articles respectively (each with silk gland). The most impressive feature is the long (at least twice the body length) and thin flagellum, which has more than 70 articles and bears numerous long setae. Such a long tail is similar to that of extant Uropygi (whip scorpions) and Palpigradi (micro whip scorpions).
Micro-CT images of the monster spider Chimerarachne yingi from the mid-Cretaceous Burmese amber. Image by HUANG Diying The international team led by Prof. HUANG Diying from NIGPAS also studied these fossil spiders and suggested that the origin of Chimerarachne can be dated back to the ancient Devonian of New York, USA (359~419 million years ago), where fragments of Attercopus were discovered. They all have characteristic spider-like chelicerae and a long whip-scorpion-like tail (flagellum). The researchers suggested that Chimerarachne is either the most primitive spider known, or else belongs to a group of extinct arachnids which were very close to spider origins. Either way, the implication is that there used to be a time when spiders still had tails. Taken together, Chimerarachne has a unique body plan among the arachnids and raises important questions about what an early spider looked like, and how the spinnerets and pedipalp organ may have evolved. These researches were recently published in Nature Ecology & Evolution titled by ‘Cretaceous arachnid Chimerarachne yingi gen. et sp. nov. illuminates spider origins’ and ‘Origin of spiders and their spinning organs illuminated by mid-Cretaceous amber fossils’.
Reconstruction of Chimerarachne yingi gen. et sp. nov. Image by YANG Dinghua Reference: 1. Wang Bo*, Dunlop J.A., Selden P.A., Garwood R.J., Shear W.A , Müller P., Lei Xiaojie, 2018. Cretaceous arachnid Chimerarachne yingi gen. et sp. nov. illuminates spider origins. Nature Ecology & Evolution. doi: 10.1038/s41559-017-0449-3. 2. Huang, Diying, Hormiga, G., Cai, Chenyang, Su, Yitong, Yin, Zongjun, Xia, Fangyuan, Giribet G., 2018. Origin of spiders and their spinning organs illuminated by mid-Cretaceous amber fossils. Nature Ecology & Evolution. doi: 10.1038/s41559-018-0475-9.
For much of the earth history, cyanobacteria were the only source of biogenic oxygen and a major source of fixed carbon and nitrogen. However, it is still not clear when cyanobacteria began to fix nitrogen. The finding of new filamentous cyanobacterial fossil from ca. 1000–720 million-year-old rocks in North China has brought dawn for the tracking of the first nitrogen-fixing cyanobacteria. The results were published in Current Biology with the title "Nitrogen-fixing heterocystous cyanobacteria in the Tonian Period". For much of the earth history, cyanobacteria were the only source of biogenic oxygen and a major source of fixed carbon and nitrogen. However, it is still not clear when cyanobacteria began to fix nitrogen. The finding of new filamentous cyanobacterial fossil from ca. 1000–720 million-year-old rocks in North China has brought dawn for the tracking of the first nitrogen-fixing cyanobacteria. The results were published in Current Biology with the title "Nitrogen-fixing heterocystous cyanobacteria in the Tonian Period". Hormogonia, paired cells, and akinetes of Anhuithrix magna. ( Image by PANG Ke) The origin of cyanobacteria had profound and transformative impacts on carbon, nitrogen, and oxygen cycles in the Earth system. Not only are cyanobacteria (and their evolutionary descendants, plastids) the only oxygenic photosynthesizers, many of them have also acquired the capability of fixing dinitrogen and one clade (including subsections IV and V, i.e., Nostocales and Stigonematales) has developed complex multicellularity with specialized nitrogen-fixing (or diazotrophic) cells known as heterocysts and resting cysts known as akinetes. But when this evolutionary innovation occurred is unknown. Molecular clock estimates of the divergence time of this clade are highly variable, ranging from ~2000 Ma to ~500 Ma. The older estimates are invariably calibrated by putative akinete fossils (described as Archaeoellipsoides) from Paleoproterozoic-Mesoproterozoic rocks around 2100–1400 Ma. The fossil record of heterocystous cyanobacteria is scarce and disputed. Most reported heterocyst and akinete fossils from Precambrian rocks are probably diagenetic or taphonomic artifacts. One of them, Archaeoellipsoides from ~2100–1400 Ma rocks, was once widely accepted as an akinete fossil, but this interpretation has been recently challenged because of the lack of associated cellular trichomes or extracellular sheath. Thus far, the earliest uncontested fossil record of heterocysts and akinetes comes from the early Devonian (~410 Ma) Rhynie Chert. The scarcity of heterocystous cyanobacterial fossils significantly hampers our understanding of the evolution of complex multicellularity and cell differentiation among cyanobacteria and their role in regulating the carbon, nitrogen, and oxygen cycles in the geological past, and our ability to calibrate cyanobacterial molecular clocks. A team of scientists led by Dr. PANG Ke from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and Mr. TANG Qing from Virginia Tech collected hundreds of specimens from a fossiliferous horizon in the Tonian Liulaobei Formation in Shouxian, Anhui Province, China. The new fossil was a mat-forming, filamentous, multicellular cyanobacterium that grew by binary cell division, reproduced by fragmentation, weathered adverse conditions by akinetes, and likely fixed nitrogen in specialized heterocysts. Anhuithrix magna represents a compelling record of akinete-forming and implicitly heterocystous and diazotrophic cyanobacteria, and attests to the evolution of cellular differentiation among multicellular cyanobacteria in the Tonian Period. As an akinete-bearing cyanobacterium, it provides a minimum age estimate of the divergence of subsections IV+V, challenges molecular clock estimates that place this divergence at ~500 Ma, and and places a firm constraint on the evolution of akinetes and heterocysts. Because nitrogenase (an enzyme responsible for catalyzing nitrogen fixation) is irreversibly inactivated by the presence of free oxygen, the evolution of heterocysts may be an evolutionary response to provide a physical shelter for nitrogenase as pO2 rose to levels that can inhibit the activity of nitrogenase. Anhuithrix magna may offer an independent constraint on the redox condition of Tonian oceans. The lack of reliable akinetes from pre-Tonian rocks despite abundant and exceptional preservation of filamentous trichomes prompts us to hypothesize that the rise of heterocystous cyanobacteria may have occurred in the Tonian. Thus, not only did cyanobacteria played a significant role in regulating the carbon and nitrogen cycles and surface Earth redox conditions, their own evolutionary trajectory was modulated by the very oxygen ultimately produced by themselves, highlighting the complex geobiological feedbacks between the biosphere and geosphere.
Stromatolites occurred in Archean, and reached their peak during the Mesoproterozoic (from 1600 to 1000 Ma). After that peak they continued to decline. Subsequently, stromatolites experienced a resurgence during the Cambrian and Early Ordovician, after early Ordovician which they decreased again and never recovered. However, the abundant stromatolites can be found in middle Ordovician strata of Ordos basin, China. During Ordovician time, the evaporitic basins are very rare, but huge evaporites including halite can be find in Ordos basin during Ordovician. The abundant stromatolites can be found in these evaporitic surroundings. Metazoan grazing and burrowing can account for the stromatolite decline after early Ordovician, but the high salinity in evaporitic surroundings of Ordos basin can help the resurgence of stromatolites in middle Ordovician evaporitic surroundings. Dr. MENG Fanwei from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and other experts found these resurgence of stromatolites in middle Ordovician evaporitic surroundings. The shallow water sedimentary evidences from bottom grown gypsum and chevron halite. Carbon isotope curve from carbonates coincides with the Middle Darriwilian excursion of the Middle Ordovician and sulfur isotope data from anhydrite imply that these strata belong to middle Ordovician. The anhydrite sulfur isotopes (δ34S) from Majiagou Formation, Ordos basin, China range from +27.1 to +28.0‰ (lower than sulfur isotopes Cambrian data, but higher than late Ordovician data) imply that these evaporites were deposited in middle Ordovician. Article information: Fan-Wei Meng, Zhi-li Zhang, Xian-qin Yan, Pei Ni,Wen-Hang Liu, Fu Fan, Gu-Wei Xie. Stromatolites in Middle Ordovician carbonate–evaporite sequences and their carbon and sulfur isotopes stratigraphy, Ordos Basin, northwestern China. Carbonates and Evaporites Stromatolite structures in drill cores from the Majiagou Formation (shallow brine) Cumulate and Chevon halite with carbonates in Majiagou Formation, Ordos basin Bottom grown Anhydrite growth structure in Majiagou Formation, Ordos basin (shallow brine)
During the last glacial period, the global mean sea level dropped about 120 meters, which caused the vast explosion of the shelf area, including in the East China Sea. Due to the sea level drop, the incised Yangtze paleo-valley was 80 meters deeper than present, where thick sediment has been accumulated during the post glacial stage. Such a thick record provides sufficient sedimentary information about the sea level and climatic changes. The last transgression during the Quaternary in the East China is called “Ammonia transgression”, which is widely distributed in this region. Based on sediments of Core (ZKA4, LZK1 and CSJA6) from the incised Yangtze paleo-valley, A total of 19 genera (26 species) of the benthic foraminifers were described and down-core variations of the foraminiferal fauna during the “Ammonia transgression” were discussed in recent published paper of Journal of Paleontology [91(6): 1102-1122, https://doi.org/10.1017/jpa.2017.66] with benthic foraminiferal SEM photo of Melonis barleeanum as the front matter. The foraminiferal fauna evolved from Ammonia beccarii var. and Florilus decorus assemblage with lower abundance and diversity, to abundant and diverse Ammonia beccarii var. and Elphidium advenum assemblage, and to the Ammonia beccarii-Elphidium magellanicum assemblage during the post-glacial period in the sections, revealed an increased seawater depth during the early post-glacial period and slight decrease since the Middle Holocene in this region. In addition to documenting the post-glacial sea level fluctuations, the benthic foraminifers also reflect a warmer climate during the early Middle Holocene. The foraminiferal difference between the different sites implies that the vicinity of upriver Core ZKA4 was first out of the influence of sea water during the late Holocene. The study was mainly made by Dr. KE Xue from China University of Geosciences (Wuhan) and Prof. LI Baohua from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, which was supported by National Natural Science Foundation of China, Strategic Priority Project of the Chinese Academy of Sciences, and the Foundation of Geological Survey of China. More information about the paper at: Ke, Xue, Li, Baohua*, Zhang, Zongyan, Wei, Yi, Hu, Fei, Fan, Dongwen, Sun, Li, Xie, Jianlei, Yu, Junjie, and Yao, Huazhou, 2017. Post-glacial Foraminifera of the incised Yangtze paleo-valley and paleoenvironmental implications. Journal of Paleontology, 91(6): 1102-1122.
SEM photo of Melonis barleeanum (23.2-23.3m, Core CSJA6, Nantong, Jiangsu Province, China), front matter of Journal of Paleontology, volume 91, No. 6.
Post-glacial Variation of Lithology, benthic foraminiferal abundance, diversity, and H(s), planktonic foraminiferal content in Cores ZKA4, LZK1, and CSJA6 from the incised Yangtze paleo-valley with reconstructed paleogeographic curve.
Selected chitinozoans As an extinct group of organic-walled microfossils, chitinozoans are characterized by a world-wide distribution and a fairly restricted biostratigraphical range, making them an efficient tool for Ordovician, Silurian and Devonian biostratigraphic investigations and precise international correlation. Lagenochitina destombesi and Euconochitina symmetrica biozones were the lowest and widely adopted chitinozoan biozones, which were also adopted in South China. However, according to our study, no typical Lagenochitina destombesi was found in South China. Besides, the base of the Euconochitina symmetrica biozone, which was previously considered as an indicator for the base of Floian, is occurring in the upper Tremadocian in South China. In the present study by Dr. LIANG Yan from Nanjing Insitute of Geology and Palaeontology, Chinese Academy of Sciences and her collegues, a rich Tremadoc chitinozoan assemblage, including 24 species of 8 genera, at the newly investigated Houtan section from the Yangtze Platform, South China was reported (Fig.1). A systematic palaeontological and statistical investigation on Lagenochitina pestovoensis and Lagenochitina destombesi shows that the index species of the L. destombesi Biozone previously described in South China is questionable (Fig.2). The L. pestovoensis Biozone is proposed to substitute the previously used L. destombesi Biozone at Houtan, South China as the lowest chitinozoan biozone in the Tremadocian. According to the previous reports and based on the materials recovered at Houtan, the Euconochitina symmetrica Biozone appears in South China clearly earlier than the Floian (Fig.3). Even more, the index species of the biozone is confined in the uppermost Tremadocian in Yiyang and Yichang areas. Nowak et al. (2016) and Amberg et al. (2017) reported E. symmetrica in the Tremadocian of Morocco (included in northern Gondwana) and northern England (Avalonia), respectively. Thus, a revision is needed to figure out the precise stratigraphical range of the E. symmetrica Biozone not only in South China, but also in other palaeocontinents, in order to allow a precise international correlation of the Tremadocian-Floian boundary by means of chitinozoan biostratigraphy. This research was funded by the National Natural Science Foundation of China, State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences. This paper is a contribution to the IGCP 653 (The Onset of the Great Ordovician Biodiversification Event). Part of the work for this manuscript was finished at the Institute of Advanced Study (IAS), Durham University and at the department of Geology, Tallinn University of Technology. Article information: Liang, Y., Servais, T., Tang, P., Liu, J.B., Wang, W.H., 2017. Tremadocian (Early Ordovician) chitinozoan biostratigraphy of South China: An update. Review of Palaeobotany and Palynology 247: 149-163. Doi: 10.1016/j.revpalbo.2017.08.008. Chitinozoan stratigraphic ranges and chrono-, bio- and lithostratigraphy of the Early Ordovician Tungtzu and Hunghuayuan formations at Houtan village of Xishui, northern Guizhou Province, with chitinozoan abundance and diversity curves on the right column.
Graptolites, one of the major groups in Ordovician oceans, sharply increased in diversity, through high evolutionary rates and a dramatic expansion of ecospace. Many preliminary studies have been conducted on graptolite diversification during the Ordovician. On a global scale, the Floian–Dapingian interval witnessed the most significant diversification of the Dichograptid fauna. A large number of taxa belonging to the Dichograptid fauna originated and subsequently diversified in this interval, which directly affected the macroevolution of three Ordovician graptolite faunas: the Anisograptid fauna, Dichograptid fauna, and Diplograptid fauna. However, on the same animal phylum on different blocks and environments may exhibit quite different macroevolutionary patterns. Thus, greater focus should be placed on collecting diversity data of one fossil group from different blocks in a regional context. Recently, Dr. LI Lixia from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and colleagues from Nanjing University investigated graptolite diversification in detail, bed-by-bed analysis, and through each graptolite biozone based on Floian–Dapingian graptolites from the Ningkuo Formation of the Nanba section in Yiyang, Hunan province, South China. In order to elucidate the graptolite diversity pattern during the Floian and Dapingian and explore the comparison of graptolite diversity within South China and other palaeoplates, as well as with different major fossil groups in South China. The possible triggering factors of graptolite diversification were also briefly discussed. The detailed study of the graptolite fauna from the Lower to Middle Ordovician Ningkuo Formation in the Nanba section, Yiyang, Hunan Province, reveals variable but generally increasing diversity during the Floian–Dapingian, peaking in the Corymbograptus deflexus Biozone. The diversification trend of graptolites in the Nanba section is broadly consistent with that in the Jiangnan region of South China and Avalonia, but is delayed compared with that in the Yangtze region of South China, Australasia, and Baltica. Furthermore, the first peak in diversity of graptolites in the Nanba section slightly post-dates that of brachiopods and conodonts, but is earlier than that for trilobites and acritarchs. Comparison of diversity trends with the sea-level curve for the Yangtze Platform reveals that the Early and Middle Ordovician graptolite radiation coincided with a transgression. Graptolite diversity trends through this interval initially reflect replacement of Anisograptid fauna by Dichograptid fauna and subsequent commencement of evolution within the Dichograptid fauna. This study is supported by the National Natural Science Foundation of China (NSFC) (Nos. 41372017, 41521061, 41290260), and the State Key Laboratory of Palaeobiology and Stratigraphy (LPS) (No. 143103). Article information: Li-Xia Li, Hong-Zhen Feng, Wen-Hui Wang, Wen-Jian Chen. 2017. Graptolite diversification during the Floian and Dapingian (Early-Middle Ordovician): A case study from the Ningkuo Formation of Hunan Province, China. Palaeoworld, 26: 431–443. Comparison of graptolite diversity curves in this study with those of Jiangnan and Yangtze regions (Zhang and Chen, 2006), Australasia, Baltica, Avalonia(Cooper et al., 2004) and Global (Chen et al., 2006). Comparison of graptolite diversity curves in this study with those of brachiopods (Zhan et al., 2005), acritarchs (Li et al., 2007), trilobites (Zhou et al., 2007),and conodonts (Wu et al., 2010) in South China.
The Yellow Sea shelf is rich in oil and natural gas. The development of Yellow Sea has important strategic significance for China's mineral resources. Qingdao Institute of Marine Geology carried several drilling in the Yellow Sea shelf and obtained up to 2800 m borehole core. Recently, Profs XU Honghe and LU Huinan from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and Dr. GUO Xingwei, Qingdao Institute of Marine Geology, carried stratigraphical and palaeontological study to the borehole core of the CSDP-2 well from the southern Yellow Sea. In this traditional study, Late Devonian plant remains, species of Archaeopteris and Sublepidodendron, and some representative miospores, are recognized from silty mudstone borehole core (well depth: 2063.1–2068.8 m). These plants have been thoroughly studied and are widely distributed in the Upper Devonian of southern China. The plant-fossil-bearing borehole core correlates to the Upper Devonian (Famennian) terrestrial to shallow-marine Wutung Formation of southern China, lower Yangtze Plate. Moreover, the Late Devonian megaplant and miospore records palaeogeographically distinguish the Sino-Korean and Yangtze Plates. The northeastern boundary of the Yangtze Plate is discussed. It is proposed that the northeastern end of the Yangtze Plate probably extends to the Imjingang Belt and the Gyeonggi Massif, the central part of the Korean Peninsula. The paper is published as below: Guo X-W, Xu H-H*, Zhu X-Q, Pang Y-M, Zhang X-H, Lu H-N, 2017. Discovery of Late Devonian plants from the southern Yellow Sea borehole of China and its palaeogeographical implications. Palaeogeography, Palaeoclimatology, Palaeoecology. Late Devonian plants, species of Archaeopteris and Sublepidodendron, from the southern Yellow Sea borehole core (well depth: 2063.1–2068.8 m).
Some representative Late Devonian miospores from the southern Yellow Sea borehole core (well depth: 2063.1–2068.8 m). Discover of the Upper Devonian in the Yellow Sea suggesting the northeastern end of the Yangtze Plate probably extends to the central part of the Korean Peninsula.
A new spinicaudatan species Ordosestheria chottsensis from the lower Barremian uppermost Bouhedma Formation of southern Tunisia. Spinicaudatans are large, bivalved crustaceans, which are common components of temporary water bodies, such as inland ponds, floodplain pools, rice field or margins of large lakes. But they can also occur in more saline environments such as large playa lakes and coastal salt flats. Their life cycle is relatively short. Some species can finish their life cycle within two to three weeks, i.e. from hatching from the eggs to the oviposition. Fossil spinicaudatans are often recovered from fine lacustrine mudstones and shales. Because of their wide distribution and quick evolution, fossil clam shrimps are very useful for the subdivision and correlation of non-marine strata. The non-marine Lower Cretaceous strata extend from Morocco to Egypt across the Saharan African, and were deposited along the southern shoreline of the Neotethyan Ocean. The dinosaur fossils from these strata provided important evidence for the breakup of Gondwana and the progressive isolation of the African continent. The non-marine sequences are also of an important socioeconomic importance as one of the global largest freshwater aquifer systems in one of the most arid regions in the world. Recently, Prof. LI Gang’s working group from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and scientists from Tunisa have recovered spinicaudatan Ordosestheria chottsensis from the lower Barremian Bouhedma Formation in the northern Chotts range of southern Tunisia. Ordosestheria was first described from the lower Aptian Jingchuan Formation of the Ordos Basin in northwestern China. The early Barremian occurrence of the genus in Tunisia suggests that ordosestheriids have most likely originated in North Africa and then dispersed to East Asia in the Aptian to become a component of the well-known Jehol Biota. Moreover, the occurrence of fossil spinicaudatans in two horizons respectively from the Bouhedma and Sidi A？ch formations indicates the interaction of freshwater and marine conditions that characterized the northern African margin as part of widespread complex paralic environments over the Chotts and Gafsa areas during the Barremian. This research was funded by Tunisian Ministry of Scientific Research, Major Basic Research Projects of the Ministry of Science and Technology, China (973 Project), and National Natural Science Foundation of China. Related information of this paper: Li, G., Boukhalfa, K., Teng, X., Soussi, M., Ben Ali, W., Ouaja, M., Houla, Y. 2017. New Early Cretaceous clam shrimps (Spinicaudata) from uppermost Bouhedma Formation of northern Chotts range, southern Tunisia: Taxonomy, stratigraphy and palaeoenvironmental implications. Cretaceous Research 72: 124-133.
High-resolution δ13C chemostratigraphy of the Ordovician succession in the Tingskullen drill core from ？land, southeastern Sweden δ13C chemostratigraphy has been accepted as a powerful tool for correlation of carbonate successions on a regional as well as global scale. A large number of studies focusing on the Ordovician Period have been published over the last ten years in order to clarify the framework of carbon isotope chemostratigraphy. Recently, Dr. WU Rongchang from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and colleagues from Lund university (Sweden) and University of Erlangen-Nürnberg (Germany) have carried out carbon isotope analysis of the Lower through Middle Ordovician cool-water carbonates of the Tingskullen core from the island of ？land in southern Sweden, revealing one of the few and most complete records of the MDICE (Middle Darriwilian Isotope Carbon Excursion) from Baltoscandia. Based on a core section penetrating the condensed Lower–Middle Ordovician succession (46 m) on the island of ？land, southeastern Sweden, this study provides an integrated scheme for carbon isotope chemostratigraphy (313 samples) and conodont biostratigraphy (29 samples) for this period. The carbonate succession in the Tingskullen core records 12 conodont zones and 6 subzones, including the Oepikodus evae, Trapezognathus diprion, Baltoniodus triangularis, B. navis, B. norrlandicus, Lenodus antivariabilis, L. variabilis, Yangtzeplacognathus crassus, Eoplacognathus pseudoplanus (Microzarkodina hagetiana and Microzarkodina ozarkodella subzones), E. suecicus, Pygodus serra (E. foliaceus, E. reclinatus, E. robustus and E. lindstroemi subzones) and Pygodus anserinus zones in ascending order. The δ13C record reveals an apparently complete record of the MDICE, including a rising limb, a well-defined peak and a falling limb. The anomaly covers a thickness of c. 27m in the core and spans the Eoplacognathus pseudoplanus, E. suecicus, Pygodus serra and P. anserinus conodont zones. Combined with the new, detailed conodont biostratigraphy, the MDICE in the Tingskullen core can be used for detailed correlation with successions from Baltica, North America, the Argentine Precordillera, South China and North China. This study is supported by the National Natural Science Foundation of China, the Swedish Research Council and Crafoord Foundation and the Deutsche Forschungsgemeinschaft. Article information: Wu, R.C., Calner, M., Lehnert, O. 2017. Integrated conodont biostratigraphy and carbon isotope chemostratigraphy in the Lower–Middle Ordovician of southern Sweden reveals a complete record of the MDICE. Geological Magazine, 154(2): 334-353. DOI:
A seven-cell specimen of Tianzhushania Recently, Dr. YIN Zongjun from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and his international colleagues from University of Bristol and Swedish Museum of Natural History published a research paper on nuclei structures in embryo-like fossils from the 609-million-year-old Ediacaran Weng’an biota. As one of the oldest plausible claims of animals in the fossil record, the embryo-like microfossils from the Ediacaran Weng’an Biota have long been expected to afford new insights into the developmental evolution of animal body plans. Furthermore, they are among the most remarkable instances of fossilization, not merely preserving component cells, but also intracellular structures. These include small features interpreted as lipid vesicles or yolk granules and Large Intracellular Structures (LISs) whose interpretation is more controversial. The LISs have a consistent size and location, sometimes occur paired in cells, positioned parallel to an anticipated plane of cell division, and can be elongated or dumbbell-shaped, suggesting possible ongoing division. They were originally considered as nuclei, spindle bundles, or other organelles and most subsequent biological interpretations have focused on a nucleus interpretation. However, this interpretation has been controversial, perhaps because details of cytokinesis have been invoked to exclude the affinity of fossils from crown-Metazoa, but also because of a prevailing notion that nuclei cannot be fossilized in early eukaryote microfossils. Hence, in this paper, Dr. Yin and his co-authors sought to test the established taphonomic models for the LISs and to reassess their origin not only to constrain affinities of these embryo-like fossils but also to better understand the early eukaryotic fossil record. Dr. YIN and his colleagues present new data on the structure, morphology, and development of the LISs in these embryo-like fossils, based on Synchrotron Radiation X-ray Tomographic Microscopy and quantitative computed tomographic analysis. These data include specimens lacking post-decay void-filling mineralization, which allows to further test alternative taphonomic models used to interpret the origin of LISs and reassess their origin. All the lines of evidence, including consistency in the number, shape, position, and relative size (LIS-to-cytoplasm ratio) of the LISs, as well as their occurrence within preserved cytoplasm, preclude their interpretation as artefacts resulting from taphonomic or diagenetic processes and support their interpretation as cell nuclei, because nuclei are the only intracellular structure that can account for the observed regularity in number, size, position, volumetric relationships of the LISs and the evidence for division in concert with the host cell. These findings confirm that the fossils are the remains of eukaryotes and not of bacteria as previously suggested. The identification of nuclei within the Weng’an Biota, along with plausible reports from Phanerozoic deposits, indicates that nuclei can be preserved in the fossil record, contrary to general expectation. Their preservation as external molds, in some instances in association with probable nucleoli, suggests that the nucleus was less susceptible to mineral replication than the surrounding cytoplasm. The reassessment of the origin of these LISs in the Weng’an embryo-like fossils has potentially important implications for understanding Precambrian microfossils, where a record of nuclei or other organelles could enable identification of early eukaryotes and help to constrain the timing and nature of eukaryotic evolution. Reports of preserved organelles in Precambrian fossils have generally lacked sufficient support and have consequently been discounted. However, the Weng’an embryo-like fossils suggest that revisiting these reports might be profitable. Article information: Zongjun Yin, John A. Cunningham, Kelly Vargas, Stefan Bengtson, Maoyan Zhu, Philip C. J. Donoghue, 2017, Nuclei and nucleoli in embryo-like fossils from the Ediacaran Weng’an Biota, Precambrian Research, Volume 301, October 2017, Pages 145-151
