With a prominent disparity in the morphology and the microfabric, stromatolites occur widely in the fossil record of the Precambrian. Noticeably, they show a long-term decline in abundance throughout the Proterozoic. The decline tendency continued in the Phanerozoic, while the Cambrian and Early Ordovician record a resurgence of microbialites. It has long been known that the Ordovician marks a changeover from microbial to metazoan-dominated reefs. However, by the Early Ordovician, the abundance of stromatolites achieved Neoproterozoic- to Mesoproterozoic- like prevalence, based on the latest rock record–normalized occurrence analyses. With a prominent disparity in the morphology and the microfabric, stromatolites occur widely in the fossil record of the Precambrian. Noticeably, they show a long-term decline in abundance throughout the Proterozoic. The decline tendency continued in the Phanerozoic, while the Cambrian and Early Ordovician record a resurgence of microbialites. It has long been known that the Ordovician marks a changeover from microbial to metazoan-dominated reefs. However, by the Early Ordovician, the abundance of stromatolites achieved Neoproterozoic- to Mesoproterozoic- like prevalence, based on the latest rock record–normalized occurrence analyses. Cooperated with Dr. Stephen Kershaw of the Brunel University, Dr. LI Qijian from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences（NIGPAS） leaded and conducted a study on the microbial reefs of the Lunshan Formation in southern Anhui Province. The team systematically collected stromatolite samples from the Lunshan Formation of various sections and conducted in-depth studies through microscopic slices. Related results have been published online in the international journal Facies. In the eastern Yangtze Platform of South China Block, Tremadocian (Early Ordovician) stromatolites occur along a palaeoenvironmental transect from the shallowest intra-platform setting through to deeper platform margin. The intra-platform and platform margin belts of Tremadocian rocks in the eastern platform are carbonate-dominated marine environments favourable for calcimicrobes. However, stromatolites are absent in siliciclastic-dominated slope facies. Shallower carbonate facies are represented by the upper member of the Lunshan Formation, composed of a hundred metres thickness of stromatolite-bearing carbonates. Such stromatolites at the Beigong section of Jinxian county are characterized by stratiform and dome-shaped laminations. Girvanella filaments are ubiquitous in thin sections (Fig 1). Crinoids grew on the surfaces of the microbialites. In contrast, towards the deeper carbonate platform margin, stromatolites in massive-bedded limestones of the upper member of Lunshan Formation of the Ma’anshan section at Shitai occur as dense columns of bindstones; macrofossils and bioclasts are rare in those stromatolites, indicating a lower energy and deeper marine setting. Water depth at the platform margin of the Ma’anshan section is interpreted as being above the base of the euphotic zone (Fig 2); however, benthic fauna notably declined. In contrast to shallower settings, in clastic-dominated locations interpreted as deposited in deeper water, stromatolites are absent, represented by the middle member of Dawuqian Formation at the Ziliqian section. This work, therefore, supports that Early Ordovician reef systems were still microbial-dominated, representing the last golden age of stromatolites. This study was financially supported by the Youth Innovation Promotion Association, the National Natural Science Foundation of China, and the Chinese Academy of Science. This study is a contribution to the IGCP-653‘The onset of the Great Ordovician Biodiversity Event’ and the IGCP Project 668 ‘The stratigraphic and magmatic history of Early Palaeozoic equatorial Gondwana and its associated evolutionary Dynamics’. Reference: Yu, Shenyang., Li, Qijian*., Kershaw, Stephen. et al. Microbial reefs in eastern Yangtze Platform, South China Block: the last golden age of stromatolites in the Ordovician. Facies 66, 12 (2020). (DOI: https://doi.org/10.1007/s10347-020-0596-x) Fig 1．Microfacies of the lithological types of the stromatolitic units, upper member of the Lunshan Formation at Beigong section of Jinxian. A) Tangled filaments of Girvanella (Gi); B) Linear and tangled filaments of Girvanella (Gi) and crinoidal fragment (Cr); C) tangled filaments of Girvanella, some filaments are recrystallized as spars, BG-3; D) calcimicrobial(Cm) encrusts on the borings of crinoid (Cr) fragments. Fig 2．Environmental reconstruction interpreting the biotic and lithological facies changes controlled by bathymetric deeping and decreased photosynthesis of marine-floor along the transition between the Lunshan and Dawuqian formations in the Tremadocian, southern Anhui.
The end-Permian mass extinction (EPME), approximately 252 million years ago (Ma), was the greatest biological and ecological crisis of the Phanerozoic Eon on Earth, which caused a serious marine and terrestrial ecosystem crisis, and about 75% of terrestrial biological species disappeared. But how long does it take for terrestrial ecosystems to recover? The end-Permian mass extinction (EPME), approximately 252 million years ago (Ma), was the greatest biological and ecological crisis of the Phanerozoic Eon on Earth, which caused a serious marine and terrestrial ecosystem crisis, and about 75% of terrestrial biological species disappeared. But how long does it take for terrestrial ecosystems to recover? Recently, the research team led by Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS) found that both lake and peat-forming forest ecosystems probably took as long as 10 million years to recover after EPME. Related results were published online in Geology on March 30, 2020. Because the subsequent Early Triassic interval was characterized by recurrent, rapid global warming, harsh marine and terrestrial conditions, marine ecosystems are thought to have recovered substantially by the middle to late Anisian, 8？10 million years and their restoration was still ongoing in the latest Triassic. However, the pattern of recovery of lacustrine ecosystems is still unclear due to the highly fragmentary freshwater fossil record. Recently, a systematic study of the Middle Triassic lacustrine sediments in the Ordos Basin by an international research group led by Prof. WANG Bo from NIGPAS, and the engineer Xie Guwei from Changqing Oilfield. The fossil-bearing horizons are also important oil-producing strata in the Changqing Oilfield. The results of isotope chronology and stratigraphy also provide new dating and fossil evidence for fine-time stratigraphic comparison and petroleum resource exploration. The research group performed high-resolution work involving stratigraphy, sedimentology, and palaeontology in three outcrops (Bawangzhuang, Mazhuang, and Yishicun) on the southern edge of the Ordos Basin. U-Pb isotopic ages of tuffaceous layers in three outcrops dated the Triassic organic-rich shale to 242 Ma in the Middle Triassic Tongchuan Formation. The organic-rich shale in the lower part of the Tongchuan Formation represents the first known appearance of a deep perennial lake after the EPME and is 5 million years earlier than any previous record. The shales have yielded abundant fossils, including microalgae, macroalgae, notostracans, ostracods, insects, fishes, and fish coprolites. The largest fish coprolites was 77 mm long in length, indicating that large predatory fish already existed in the lake at that time. The chitinous mandibles of predatory dipteran larvae were found in phosphatized coprolites. The results provide data on the earliest known Triassic complex lacustrine ecosystem. Primary producers included various micro- and macroalgae, together with some notostracans, ostracods and insects that fed on algae as primary consumers. Second-level consumers included some predatory insects, with higher order trophic levels being represented by predatory fish. Such an ecosystem is a key component of Mesozoic lakes, which were different from pre-Mesozoic lakes in which dipteran larvae were absent and aquatic beetles were rare. The restoration of a complex lacustrine ecosystem was coincident with the termination of the ‘coal gap’, which was an interval of approximately10 million years when no coals were deposited worldwide. It is generally believed that the reoccurrence of the Middle Triassic coal seam represents a significant restoration of the forest ecosystem after EPME. In the Ordos Basin, the oldest known Triassic coal seam occurs in the uppermost part of the Ermaying Formation, the age of which is slightly greater than that of the organic-rich shale in the bottom of the Tongchuan Formation. The appearance of Triassic coal seams is generally considered to represent the substantial recovery of peat-forming forests following the mass extinction, suggesting that lakes and forest ecosystems may be tightly linked through biological, physical, and chemical interactions. Therefore, both lake and peat-forming forest ecosystems probably took up to 10 million years to recover, much longer than the period of recovery of plant communities inferred from palynological data. The hot Early Triassic climate would have limited dissolved oxygen in lakes, potentially hindering ecosystem recovery. A subsequent major increase in marine carbon burial in the Anisian could, however, have caused CO2 drawdown and global cooling, improving lacustrine conditions. In addition, the abundant volcanic ash likely transferred nutrients into the water and probably significantly increased the efficiency of primary productivity in the Ordos Basin. Therefore, both the climatic cooling and high volcanic nutrient input most likely facilitated development of this complex lake community. Relevant research work was jointly funded by the Chinese Academy of Sciences and the National Natural Science Foundation of China. Reference: Zhao Xiangdong, Zheng Daran, Xie Guwei, Jenkyns H.C., Guan Chengguo, Fang Yanan, He Jing, Yuan Xiaoqi, Xue Naihua, Wang He, Li Sha, Jarzembowski E.A., Zhang Haichun, Wang Bo* (2020) Recovery of lacustrine ecosystems after the end-Permian mass extinction. Geology, doi:10.1130/G47502.1.
Figure 1: Field photographs of study area (Imaged by NIGPAS) Figure 2: Photographs showing representative lithologies and collected samples for U-Pb dating (Imaged by NIGPAS) Figure 3: Stratigraphic column showing lithologies, fossiliferous horizons, sample points and age results (Imaged by NIGPAS) Figure 4: Representative fossils from the organic-rich shale and mudstone of the Tongchuan Formation. (A-C) Fish coprolites. (D and E) Sliced photomicrographs of fish coprolite. (F and G) Beetles. (H) Fish. (I) Ostracoda. (J) Tadpole shrimp (Imaged by NIGPAS)
Mesopsychoid scorpionflies are peculiar Mesozoic insects with a distinctly elongate mouthpart and are considered to be a critical group of pollinators prior to the rise of angiosperms. A new genus found from 99-million-year-old Burmese amber reveals the origin of scorpionflies’ long mouthpart. This discovery was reported in Science Advances on March 4.
Mesopsychoid scorpionflies are peculiar Mesozoic insects with a distinctly elongate mouthpart and are considered to be a critical group of pollinators prior to the rise of angiosperms. A new genus found from 99-million-year-old Burmese amber reveals the origin of scorpionflies’ long mouthpart. This discovery was reported in Science Advances on March 4. Aneuretopsychidae is a family of mecopteran insects with a long siphonate mouthpart. In particular, this family is the key to understanding both the early evolution of highly modified mouthparts in Mesopsychoidea and arguably the origin of fleas. Previously, all known aneuretopsychids were from compression fossils, and the detailed structure of their mouthparts was still unclear. Now, however, an international research group led by Prof. WANG Bo from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) has found a new genus, including two new aneuretopsychid species from early Late Cretaceous (99 million years ago) Burmese amber, which reveals new anatomically significant details of the elongate mouthpart elements. The aneuretopsychid mouthpart in the new amber fossils consists of one pair of galeae and one unpaired central hypopharynx. During feeding, the galeae would come together temporarily and enclose the hypopharynx thus forming a functional tube. The structures of the new three-dimensionally preserved fossils thus reveal that the aneuretopsychid mouthpart is not labial but maxillary in origin. The phylogenetic results based on 38 taxa and 54 discrete characters support the monophyly of Mesopsychoidea and demonstrate that an elongate mouthpart is one of its key synapomorphies, challenging the view that the long-proboscid condition independently originated two or three times in this clade. In addition, the mouthpart of Mesopsychoidea differs structurally from the highly modified piercing mouthparts of Siphonaptera. So, neither Aneuretopsychidae nor Mesopsychoidea is a sister group to Siphonaptera. In the Burmese amber forest, at least five families of long-proboscid insects have been discovered, further revealing the variety and complexity of mid-Cretaceous pollinating insects. This study provides new insights into the separate origin of the long mouthpart of Mesopsychoidea and fleas, and the evolution of Cretaceous pollinating insects. Reference: Zhao Xiangdong, Wang Bo*, Bashkuev A.S., Aria C., Zhang Qingqing, Zhang Haichun, Tang Wentao, Engel M.S. (2020) Mouthpart homologies and life habits of Mesozoic long-proboscid scorpionflies. Science Advances, 6: eaay1259. Aneuretopsychidae from Late Cretaceous Burmese amber（Image by NIGPAS） Ecological reconstruction of Mesozoic Aneuretopsychidae (Image by NIGPAS)
When and how animal ancestors made the transition from single-celled microbes to complex multicellular organisms is unclear. But a new scientific study suggests animal-like embryological traits developed long before animals themselves. Proposed life cycle of Caveasphaera (Image by NIGPAS) Animals evolved from single-celled ancestors before diversifying into 30-40 distinct anatomical designs. When and how animal ancestors made the transition from single-celled microbes to complex multicellular organisms is unclear. But a new scientific study suggests animal-like embryological traits developed long before animals themselves. The research – by an international research team led by scientists from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) and the University of Bristol – focused on ancient fossils of Caveasphaera, a multicellular organism found in 609-million-year-old rocks in South China’s Guizhou Province that defies easy definition as animal or non-animal. Using X-ray microscopy, the researchers analyzed the tiny fossils, which measure about a half-millimeter in diameter and were preserved down to their component cells. Various fossils displayed different stages of Caveasphaera development – from a single cell to a multicellular organism. “We were able to sort the fossils into growth stages, reconstructing the embryology of Caveasphaera,” said Kelly Vargas from the University of Bristol. YIN Zongjun of NIGPAS interpreted the discovery: “Our results show that Caveasphaera sorted its cells during embryo development in just the same way as living animals, including humans.” YIN emphasized, however, there is “no evidence that these embryos developed into more complex organisms.” Still, the discovery offers the earliest evidence of a key step in the evolution of animals – the capacity to develop distinct tissue layers and organs. The verdict still seems to be out on whether Caveasphaera was itself an animal or just an important step in animal evolution, even as researchers search for more fossils. Co-author ZHU Maoyan of NIGPAS said, “Caveasphaera looks a lot like the embryos of some starfish and corals – we don’t find the adult stages simply because they are harder to fossilize.” Whatever Caveasphaera turns out to be, its fossils tell us that animal-like embryonic development evolved long before the oldest definitive animals appeared in the fossil record. This research was funded through the Biosphere Evolution, Transitions and Resilience (BETR) programme, which is co-funded by the UK’s Natural Environment Research Council (NERC) and the Natural Science Foundation of China (NSFC). Reference: The early Ediacaran Caveasphaera foreshadows the evolutionary origin of animal-like embryology’ by Z. Yin, K. Vargas, J. Cunningham, S. Bengtson, M. Zhu, F. Marone and P. Donoghue, Current Biology. https://doi.org/10.1016/j.cub.2019.10.057
Scientists have long been unclear as to when insect pollination first appeared. Now, an international research group from China and the U.S. has provided the earliest evidence of insect-angiosperm pollination – by analyzing a sample of Cretaceous Burmese amber. Results were published in Proceedings of the National Academy of Sciences (PNAS) on November 11. Most of our food is from angiosperms, while more than 90% of angiosperms require insect pollination – making this pollination method hugely important. Nevertheless, scientists have long been unclear as to when insect pollination first appeared. Now, however, an international research group from China and the U.S. has provided the earliest evidence of insect-angiosperm pollination – by analyzing a sample of Cretaceous Burmese amber. The research was led by Prof. WANG Bo from the Nanjing Institute of Geology and Palaeontology (NIGPAS) of the Chinese Academy of Sciences. Results were published in Proceedings of the National Academy of Sciences (PNAS) on November 11. Angiosperms, also known as flowering plants, originated in the Mesozoic and are the most diverse group of land plants, with approximately 300,000 known species. Their most distinguishing characteristic is the presence of true flowers. Angiosperms self-pollinate as well as use insects, animals, wind and water to achieve pollination, thus enhancing gene flow and increasing diversity. Angiosperms experienced rapid radiation by the mid-Cretaceous, which Darwin called an “abominable mystery.” Since Darwin’s time, numerous scholars have thought that insect pollination must be a key contributor to the Cretaceous radiation of angiosperms since insects and flowering plants were both common by this time. However, direct evidence of a Cretaceous insect-angiosperm pollination mode was missing and related theories remained hypothetical until now. Working with Burmese amber dating to the mid-Cretaceous – 99 million years ago – the researchers discovered evidence of beetle pollination, thus confirming the hypothesis of Cretaceous insect-angiosperm interaction and offering the earliest evidence for entomophily. The beetle specimen in the amber sample is a new species within the family Mordellidae, named Angimordella burmitina. Extant Mordellidae beetles are a typical flower-visiting group. Commonly, they are known as “tumbling flower beetles” for the irregular movements they make when escaping predators, due to having an elongated pygidium (an external posterior body part or shield in arthropods). A. burmitina is distinguished from most extant species by a poorly developed pygidium and enlarged, very well-developed hind legs. Based on these features, the scientists believe A. burmitina utilized a different movement mechanism than other species, preferring to jump or fly between corollas and plants. The mouth part of A. burmitina is also highly evolved for pollen collection, with enlargement of part of the maxillary palps, which are leg-like structures near the mouth. Numerous pollen grains were preserved on or near the A. burmitina specimen. To examine them closely, the research team performed high-precision grinding and polishing of the amber sample, then applied confocal laser scanning microscopy and optical photomicrography. Using these methods, the scientists identified the pollen grains as tricolpate, meaning they each have three pores and come from a type of flowering plant known as a eudicot. Their surface texture, size, and clumping also show that the pollen is zoophilous, making it more likely to be picked up by an animal such as a beetle. Based on the entomological and palynological evidence, the research team believes this amber specimen reveals a beetle-angiosperm pollination mode, supporting the hypothesis that specialized insect pollination modes were present in eudicots at least 99 million years ago. Previous evidence of insect pollination of flowering plants dates to the Middle Eocene, around 45-48 million years ago. Thus, the current finding extends the history of insect pollination of flowering plants by around 50 million years and suggests that such mutualism existed at least as far back as 99 million years ago. Reference: Bao Tong, Wang Bo, Li Jianguo, Dilcher D. (2019) Pollination of Cretaceous flowers. PNAS, doi:10.1073/pnas.1916186116.
Cretaceous tumbling flower beetle and tricolpate pollen grains.(Imaged by NIGPAS) Ecological reconstruction of the Cretaceous tumbling flower beetle.(Imaged by NIGPAS)
Chirality is present at all scales from molecule to galaxy, and plants are not exceptional. Plants with twisted axes are usually climbing “twiners”. In extant twiners, more than 90% of them prefer fixed right-handed helices. However, researchers reported in Current Biology that a Permian fern fossil possessed a fixed left-handed twining direction.
The origin of homochirality in nature was one of 125 great unanswered questions suggested by Science. Chirality is present at all scales from molecule to galaxy, and plants are not exceptional. Plants with twisted axes are usually climbing “twiners”. In extant twiners, more than 90% of them prefer fixed right-handed helices. However, researchers reported in Current Biology that a Permian fern fossil possessed a fixed left-handed twining direction. In geological history, the climbing habit may have already been present in the first Middle Devonian forests as indicated by possible climbers among aneurophytalean progymnosperms and lycopsids. By late Carboniferous climbing was more common and diverse as preserved in swamp forests with modes of attachment ranging from aerial roots to appendages modified into hooks and tendrils. However, direct preservation of a fossil twiner has only been documented in the Miocene Shanwang Formation of Eastern China (ca. 16 Ma), albeit with the identity of the twiner difficult to establish and likely to be a self-twiner. Recently, researchers form the Nanjing Institute of Geology and Palaeontology, CAS, China, the West Bohemian Museum in Pilsen, Czech Republic and the Stanford University, USA reported a new fossil twiner from the early Permian Wuda Tuff fossil Lagerst？tte of Inner Mongolia, China (ca. 298 Ma). The complete rotation confirms the twining habit dating back to the Paleozoic. The high fidelity of 3-D preservation allows the identification of the twiner and host plant. The twiner possesses a slightly C-shaped xylem strand anatomy without any secondary tissues and is thereby interpreted as a fern rachis. The associated plant fragments and attached pinnules from another twining specimen indicate the twiner to be an anachoropterid fern, which possesses a fixed left-handed twining direction. The host possesses a eustelic stem anatomy that generally indicates a seed plant affinity. It can be further classified as Callistophytales on account of additional material with the same stem anatomy and prickle structures collected from the same forest. Moreover, the host possesses heterophyllous pinnules on their fronds with some pinnules modified into pinnate linear lobes that terminate in swollen structures previously interpreted from similar material as adhesive pads, suggesting that the host plant is also a climber. The dual-climbing phenomenon is known from modern tropical and subtropical forests, but has never been documented in the fossil record. Although indirect evidence of the climbing habit was already common from the late Carboniferous tropical forest ecosystems, here direct preservation of the twining habit as well evidence of the dual-climbing phenomenon, indicating a high degree of ecological complexity in early Permian swamp forests. The study was supported by the Strategic Priority Research Program (B) of Chinese Academy of Sciences, the National Natural Science Foundation of China, the State Key Laboratory of Palaeobiology and Stratigraphy, and the Grant Agency of Czech Republic. Reference: Weiming Zhou, Dandan Li, Josef Psenicka, C. Kevin Boyce, Jun Wang*, 2019. A left-handed fern twiner in a Permian swamp forest. Current Biology. DOI:10.1016/j.cub.2019.10.005 Reconstruction of the dual-climbing phenomenon. (Imaged by NIGPAS)
The death march of a segmented bilaterian animal unearthed from ~550-million-year-old rocks in China shows that the oldest mobile and segmented animals evolved by the Ediacaran Period (635-539 million years ago). The research was published in Nature on Sept. 4 by an international research team from China and the U.S. Yilingia spiciformis body fossil (left), trace (right), and artist’s reconstruction (middle). (Image by NIGPAS) The death march of a segmented bilaterian animal unearthed from ~550-million-year-old rocks in China shows that the oldest mobile and segmented animals evolved by the Ediacaran Period (635-539 million years ago). The research was published in Nature on Sept. 4 by an international research team from China and the U.S. The origin of bilaterally symmetric animals (or bilaterians) with a segmented body plan is a monumental event in early animal evolution. Although scientists have estimated, on the basis of molecular clock analyses, that mobile and segmented bilaterians evolved in the Ediacaran Period, no convincing fossil evidence had been found to substantiate these estimates. Recently, however, an international research team from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences and Virginia Tech in the United States reported the discovery of a segmented bilaterian fossil preserved in ~550-million-year-old rocks in China. What makes this fossil unusual is that it is directly connected with a trail it made. The new fossil indicates that mobile and segmented animals evolved by the terminal Ediacaran Period. It also helps scientists understand the producers of Ediacaran trace fossils, since such fossils are often not preserved with their trace makers. The new fossil species, found in the terminal Ediacaran Shibantan Formation of the Dengying Formation in the Yangtze Gorges area, is Yilingia spiciformis. It is an elongate and segmented bilaterian with repetitive and trilobate body units, which show anteroposterior and dorsoventral differentiation. One specimen is directly connected with the trace it produced immediately before death, thus allowing the authors to interpret other similar trace fossils that are preserved in the same unit but are not directly connected with the animals that produced them. The direct association with trace fossils suggests that Yilingia spiciformis was a mobile animal capable of locomotion. Evidence of body segmentation, polarity, and directional locomotion indicates that Yilingia spiciformis was a bilaterian animal. However, it is difficult to determine its exact phylogenetic position within the bilaterian family tree. The authors surmise that Yilingia spiciformis could be related to arthropods or annelids. As one of the few Ediacaran animals demonstrably capable of producing long and continuous trails, Yilingia spiciformis sheds new light on the origin of segmentation and its possible relationship with animal motility. The emergence of motile animals had a profound environmental and ecological impact on Earth surface systems and ultimately led to the Cambrian substrate and agronomic revolutions. The study was supported by the Chinese Academy of Sciences, the Ministry of Science and Technology of China, the National Natural Science Foundation of China, the U.S. National Science Foundation, and the National Geographic Society. Reference: Zhe Chen, Chuanming Zhou, Xunlai Yuan*, Shuhai Xiao*, 2019, Death march of a segmented and trilobate bilaterian elucidates early animal evolution. Nature, https://doi.org/10.1038/s41586-019-1522-7
Chitinozoans are organic-walled microfossils widely recorded in Ordovician to Devonian (about 400 million years ago) marine sediments and usually shaped like “bottles”, however, with a hitherto-unknown biologic affinity and used to be considered as metazoan eggs. Recently, researchers from China, Estonia and USA suggested that chitinozoans are more likely to be fossils of individual microorganisms rather than eggs. The results were published online on July 31, 2019 in Proceedings of the Royal Society B. Chitinozoans are organic-walled microfossils widely recorded in Ordovician to Devonian (about 400 million years ago) marine sediments and usually shaped like "bottles". Their biological affinity remains unknown, but most commonly, they are interpreted as eggs of marine metazoans. Recently, researchers from China, Estonia and USA suggested that chitinozoans are more likely to be fossils of individual microorganisms rather than eggs. The results were published online in Proceedings of the Royal Society B on July 31, 2019. Since their first description in the 1930s, multiple hypotheses have been put forward trying to explain their biological origin and ecology, including classification as protists, metazoans or egg capsules of metazoans. With the first report of some cocoon-like preservation in Desmochitina, chitinozoans have almost exclusively been interpreted as eggs of unknown marine metazoans, possibly some wormlike animals, during the last three decades. No further discussions related to their affinity have been advanced since then, even though the egg hypothesis makes no allowance for, nor does it explain, some of the morphological structures found in Chitinozoa. However, in a recent study conducted by Dr. LIANG Yan from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) and her collaborators, the researchers re-evaluated the egg hypothesis from the perspective of morphological variation of chitinozoans. They conducted a detailed case study focusing on single highly variable species Hercochitina violana sp. nov. in order to allow for a more quantitative analysis. The scientists compiled a dataset of measurements of 378 randomly selected species representing all 57 chitinozoan genera currently known, as well as a dataset of coefficients of variation (CV) in eggs from 45 extant aquatic metazoan species. For the first time, this allowed a reliable comparison of the magnitude of size variation between chitinozoans and undisputed eggs to further assess their possible analogy. The results showed that the range of variation in most chitinozoans was much larger than that of eggs of extant marine invertebrates or the hitherto reported undisputed fossil eggs. The range and type of size variation shown in Hercochitina violana sp. nov. potentially indicated an ontogenetic series rather than an intraspecific variation. Additionally, there is no analogue in extant metazoan eggs which have such complicated and delicate structures as developed in chitinozoans, not to mention the rapid evolutionary trend of ornamentations, which is also inconsistent with the prevailing egg hypothesis. It is more plausible to argue that most chitinozoans, with the exception of the unique Desmochitina, represent independent organic-walled microorganisms rather than eggs of metazoans. Reference: Liang Y*, Bernardo J, Goldman D, Nolvak J, Tang P, Wang W, Hints O*. 2019 Morphological variation suggests that chitinozoans may be fossils of individual microorganisms rather than metazoan eggs. Proc. R. Soc. B 20191270.
SEM images of Hercochitina violana sp. nov. showing the morphologic variation. (Image by NIGPAS)
The climate on the earth has gradually warmed up since the last glacial maximum some 20,000 years ago. Appropriate climate conditions have contributed to the formation and development of the Holocene farming culture. The way of production and lifestyle for the ancient people gradually changed from the early collecting, fishing and hunting to the later settled production with farming agriculture. This change in production and lifestyle was closely related to the environment variations at that time, and had a great impact on the development of human civilization. Vegetation in southern China has undergone significant changes since the last glacial maximum. Given the limitations of data, we still lack a comprehensive understanding of the concrete changing process and its relationship with human farming life. In order to better understand the variations of vegetation with climate fluctuation since the last glacial maximum in southern China, as well as the impact of human activities on vegetation, a research team consisting of Prof. WANG Weiming, Dr. SHU Junwu and Dr. CHEN Wei from Nanjing Institute of Geology and Palaeontology of Chinese Academy of Sciences, and Dr. LI Chunhai from Nanjing Institute of Geography and Limnology of Chinese Academy of Sciences, has carried out pollen study for 20 drilling cores in some less researched areas. Finally, pollen data from 14 sites have been selected for the restoration of vegetation over the past 20,000 years. The research results have recently been published on the journal Chinese Science: Earth Sciences. The research team gave for the first time the vegetation zoning maps around 18 ka BP, 9 ka BP and 6 ka BP respectively, and the distribution characteristics of plants in each zone/subzone are described. The main results are as follows: 1) The variation of vegetation in southern China since about 20,000 years generally coincides with the changing process of global climate after the last glacial maximum. Temperate vegetation around 18 ka BP can extends southward to the present south subtropical subzone, reflecting that the nature of vegetation still retained some climatic characteristics of the previous glacial period, although the climate had begun to warm up at that time. 2) During the Holocene megathermal, the characteristics of vegetation in the study area are rather distinct, which indicates similar features around both 9 ka BP and 6 ka BP. This reflects the general trend of global warming at that time on the one hand, and the overall control of southeast monsoon and southwest monsoon in southern China on the other hand. It is speculated that the long-term strong monsoon climate since 9 ka may be the main reason for the dominant vegetation distribution at that time, and its gradual convergence with the present. 3) High-resolution palynological study shows that although some climatic events since the last glacial maximum have been documented in some stratigraphic profiles, they have limited impact on the overall nature of local vegetation. In addition to the global climate change, the vegetation in the study area is also affected by the evolution and development of monsoon climate. 4) Human activities are not clearly reflected in 9 ka BP and 6 ka BP vegetation maps, which indicates that early farming activities have little influence on the original vegetation. The impact of human activities on vegetation is generally earlier in the middle and lower reaches of the Yangtze River than in the other areas of southern China, and the impact is more distinct. 5) The rise of sea level during the Holocene megathermal might also affect the distribution of vegetation at that time. Large-scale transgressions were recorded in Lake Dongqian, Lake Baima and Lake Xianghu in the early Holocene. This work was supported by the Strategic Priority Research Program of Chinese Academy of Sciences and the National Natural Science Foundation of China. Reference: Wang W*, Li C, Shu J, Chen W. 2019. Changes of vegetation in southern China. Science China Earth Sciences, https://doi.org/10.1007/s11430-018-9364-9
Geographic location map of newly added boreholes and boreholes in documents. solid dots, Newly added boreholes; hollow dots, boreholes in documents
Vegetation zoning map in southern China. (a) Modern vegetation zoning map; (b) 18 ka BP vegetation zoning map; (c) 9 ka BP vegetation zoning map; (d) 6 ka BP vegetation zoning map Contact: Prof. Wang Weiming, Principal Investigator Email: wmwang@nigpas.ac.cn Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences Nanjing, Jiangsu 210008, China
