The end-Ordovician mass extinction (EOME) was the first of the “Big Five” extinctions of the Phanerozoic. It is widely interpreted as consisting of two pulses associated with the onset and demise of the Gondwana glaciation, respectively, with the second pulse eradicating the distinctive, glacially related Hirnantian benthic biota (HBB). This two-pulse model has become a widely accepted paradigm within which tempo, magnitude, pattern and dynamics of the EOME and the subsequent recovery have been variously interpreted.Recent investigations in South China, however, indicate an erroneous temporal and causal link between the “HBB” and the Gondwanan glaciation, which, if confirmed globally, will hence underpin a critical reevaluation of the tempo and nature of the EOME.To further elucidate this key issue, Dr. WANG Guangxu from the Nanjing Institute of Geology and Palaeontology of Chinese Academy of Sciences and his colleagues made a global review of occurrence data of latest Ordovician benthic marine organisms, which reveals that virtually all warm-water benthic assemblages previously assigned to the HBB comprise two distinct and clearly postglacial faunas, both younger (middle and late Hirnantian, respectively) than the cool-water Hirnantia fauna (latest Katian to early Hirnantian).The newly recognised three Transitional Benthic Faunas (i.e., TBFs 1–3) can be closely tied to graptolite, conodont, and chitinozoan biozonations, the Hirnantian Isotope Carbon Excursion (HICE), and the glaciation, thereby providing an integrated, much higher resolution timescale for understanding the tempo and nature of the EOME.At such a finer resolution, these authors also postulate a more profound impact of the first pulse of the EOME than hitherto envisaged, as evidenced by opportunistic expansion of the Hirnantia fauna globally and the complete absence of metazoan reefs in its immediate aftermath. They also argue, based on high-quality data from well-documented benthic groups in South China (i.e., brachiopods, tabulate and rugose corals, trilobites, and sponges), that the magnitude of the second pulse of the EOME caused by the deglaciation has been overestimated because the two postglacial faunas (i.e., TBFs 2–3) were part of a subsequent recovery phase of marine ecosystems rather than contributing to biodiversity decline. Thus, they reinterpret the EOME as a single-pulse, rapid event that was followed by a prolonged initial recovery intermittently impeded by climatic shocks through the Hirnantian, prior to the onset of a progressive reestablishment of marine ecosystems during the early Silurian (Rhuddanian and Aeronian) associated with an overall amelioration of climatic conditions.Reference: Wang, G.X., Zhan, R.B. and Percival, I.G., 2019. The end-Ordovician mass extinction: A single-pulse event? Earth-Science Reviews, 192: 15–33. Models of latitudinal patterns of TBFs 1–3 through the Hirnantian. A refined integrated Hirnantian stratigraphic framework, against which biotic and environmental changes across the EOME are also shown.
During the Ordovician, most Chinese continental blocks were located near the tropical area around the Gondwanan supercontinent, containing South and North China, Tarim, Himalaya, Lhasa and Sibumasu (Baoshan). Their paleogeographic locations and movements have always been research hotspots. Recently, Dr. FANG Xiang and Prof. ZHANG Yuandong from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, and Prof. Clive Burrett from Mahasarakham University, Thailand, conducted a quantitative statistical analysis of Middle to Late Ordovician cephalopods from the northeastern peri-Gondwana region, in order to reconstruct palaeobiogeographic distributions and their dynamic variation which indicate palaeoplate movements during the Middle to Late Ordovician Cephalopods have a very strong swimming ability. But because of the septal strength index, cephalopods would implode if they got deeper than their limited depth. Based on studies on living Nautilus, cephalopods need to rest on the sea floor after swimming for a long time. We can use this to assess the palaeogeographic provincialism of cephalopods and then speculate on the relative dynamic locations of Gondwana and the Asian blocks. In this study, based on published literature and the latest palaeontological researches on South China, several statistical methods, including cluster analysis, nonmetric multidimensional scaling and network analysis, of Middle to Late Ordovician cephalopod occurrences in the northeastern peri-Gondwanan region were conducted. For the Middle Ordovician, three biogeographic provinces may be recognized in the northeastern peri-Gondwana region: the Australia, the North China–Tibet–Sibumasu (NTS), and the South China–Altun (SA) provinces. However, this biogeographic pattern changed significantly in the Late Ordovician, when the cephalopods in the Tibetan and Sibumasu terranes changed markedly to show greater similarity to South China, and form the South China–Tarim–Tibet–Sibumasu (STTS) Province. The study shows that different composition of these two provinces and different types of cephalopods indicating that during the Middle Ordovician, the NTS province should be located in the tropical zones, and SA province in a slightly higher latitude region. During the Late Ordovician, South China was drifting slowly northwards, closer to Australia, meanwhile North China was drifting gradually away from northeastern peri-Gondwana. This dynamic variation of cephalopod provincialism for Middle and Late Ordovician cephalopods was related to alterations of palaeolatitude and the changing locations of the palaeoplates during the Middle and Late Ordovician. This study was financially supported by the National Natural Science Foundation of China, Ministry of Science and Technology of China and Chinese Academy of Sciences. This study is a contribution to IGCP projects 653 and 668. Reference: Xiang Fang*, Clive Burrett, Wenjie Li, Yunbai Zhang, Yuandong Zhang, Tingen Chen, Xuejin Wu, Dynamic variation of Middle to Late Ordovician cephalopod provincialism in the northeastern peri-Gondwana region and its implications. Palaeogeography, Palaeoclimatology, Palaeoecology, 521: 127-137. https://doi.org/10.1016/j.palaeo.2019.02.015 Cluster analysis (upper left), nonmetric multidimensional scaling (lower left) and network analysis (right) recognize the palaeobiogeographic provinces in Middle and Late Ordovician Published typical cephalopods from NTS Province in the Middle Ordovician (left) and published typical cephalopods from STTS Province in the Late Ordovician (right)
Recently, an international team led by Prof. ZHOU Chuanming from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences reported two new high-precision U-Pb zircon dating data from two layers above the Cryogenian Sturtian and Marinoan in South China, which provides evidence for the globally synchronous and rapid termination of Cryogenian glaciations. The result and related analysis were published in Geology.Cryogenian Sturtian and Marinoan glaciations represent the most severe paleoclimatic events in Earth history. The global distribution of presumably synchronous Cryogenian glacial deposits is one of the key observations that stimulated the initial formulation of the Snowball Earth Hypothesis or SEH. The formalization of the SEH leads to explicit predictions about the global synchroneity and duration of Cryogenian Snowball Earth glaciations. Specifically, the SEH predicts a globally synchronous and rapid termination of Cryogenian glaciations on the time scale of 103–104 years.Wherever the deglaciation began is difficult to define in the sedimentary record, the sharp transition from glacial diamictite to postglacial cap dolostone, which represents a landmark event during deglaciation, can be used to demarcate the final stage of deglaciation. A direct test of rapid and globally synchronous deglaciation requires high-resolution (better than ± 1.0 Ma) geochronological data to tightly bracket the transition from diamictite to cap dolostone in multiple paleocontinents or basins.Currently available geochronological data are consistent with the occurrence of two global glaciations in the Cryogenian Period (~ 720？635 Ma), i.e., the Sturtian and Marinoan glaciations. However, high-precision radiometric dates are few and do not have a sufficient paleogeographic and stratigraphic coverage to allow a positive test of global synchroneity and rapidity as predicted by the SEH. For example, on the basis of currently available data, the Marinoan deglaciation in Australia, Namibia, and South China are constrained to be <636.41 ± 0.45 Ma, <635.21 ± 0.59 Ma, and between 636.3 ± 4.9 Ma and 635.23 ± 0.57 Ma, respectively. These ages, while consistent with global synchroneity, are not sufficient to determine synchronous deglaciation among these three paleocontinents. Thus, to positively determine global synchroneity and rapidity of Cryogenian deglaciation events, we need more high-precision radiometric dates from glaciogenic diamictite and postglacial cap dolostone to tightly bracket the final deglaciation on each paleocontinent. To this end, Prof. ZHOU Chuanming and colleagues from the University of California at Davis and Virginia Tech, reported two new high-precision U-Pb zircon CA-ID-TIMS of 658.80 ± 0.50 Ma and 634.57 ± 0.88 Ma from tuffaceous layers that occur, respectively, within the cap dolostone atop the Tiesi’ao diamictite (Sturtian age) and at the topmost Nantuo diamictite (Marinoan age) in South China. The 658.80 ± 0.50 Ma age represents a high-precision minimum age constraint on the termination of the Sturtian-age glaciation. The 634.57 ± 0.88 Ma age and a previously published age of 635.23 ± 0.57 Ma from the topmost cap dolostone are indistinguishable within uncertainty, and together they provide tight constraints on the termination of the Marinoan glaciation in South China at ca. 635 Ma and directly bracket the duration of the cap dolostone to be <106 yrs. The new data support the rapid termination of the Marinoan glaciation in South China and are consistent with global synchroneity of Cryogenian deglaciation events. To positively test whether the same is true on other continents and for the Sturtian deglaciation requires additional high-resolution ages on each paleocontinent.Reference: Chuanming Zhou, M. H. Huyskens, Xianguo Lang, Shuhai Xiao, Qing-Zhu Yin, 2019. Calibrating the terminations of Cryogenian global glaciations. Geology, 47: 251-254. https:// doi .org /10 .1130 /G45719.1 206Pb/238U ages of individual zircons for samples 17LSJ-17 and ES-1 Compilations of radiometric ages and their relationship with the supposed Sturtian and Marinoan glaciations on different continents.
The hyperdiverse rove beetle genus Stenus (Steninae) has one of the most specialized prey-capture structures known from extant arthropods. They use a ‘tongue’-like apparatus formed by a protrusible labium with terminal sticky cushions and a haemolymph pressure to catch fast-fleeing prey. Fossils with an exposed apparatus are exceedingly rare. Mesozoic stenines are therefore significant for elucidating the early evolution of the group. Recently, an international team led by Dr. CAI Chenyang, from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences, reported two species of the extinct stenine genus Festenus from mid-Cretaceous Burmese amber, some 99 million years ago, which provides important information about the origin and early evolution of both the novel predatory structure and of the beetle subfamily. Steninae include three extant genera: the widespread Stenus, the Holarctic Dianous, and a new genus from Australia. Living in various microhabitats, extant Stenus species prey on fast-fleeing springtails and other small animals. The species of Dianous lack such a protrusible labium. Dr. Cai and his colleagues examined over 120 individuals of Steninae, and found an exposed prey-capture apparatus in only two specimens. The ‘tongue’-like apparatus displays a generalized form, just as that in extant species such as Stenus comma. Therefore, like modern Stenus species, these fossil stenine rove beetles were likely able to catch small-sized animals such as springtails using their sticky apparatus. The discovery of direct evidence of a protrusible prey-capture apparatus in one of the earliest known stenine beetles from the Cretaceous illuminates their early evolution and confirms an ancient origin for their derived predatory behavior. Molecular phylogenetic studies of selected species of Stenus and Dianous indicated an origin of Dianous within Stenus, suggesting a secondary loss of the harpoon apparatus. The presence of a protrusible prey-capture apparatus has been considered the most prominent apomorphic character for Stenus, but this assumption is rejected the new disveorey of these Mesozoic Steninae with specialized prey-capture apparatus Reference: Chenyang Cai*, D.J. Clarke, Ziwei Yin, Yanzhe Fu, Diying Huang, 2019. A specialized prey-capture apparatus in mid-Cretaceous rove beetles. Current Biology. DOI: 10.1016/j.cub.2019.01.002. Specialized prey-capture apparatus in an extant Stenus species. Specialized prey-capture apparatus in mid-Cretaceous stenine rove beetles.
Anchiornis, one of the earliest feathered dinosaurs ever discovered, was found to have the ability to fly. However, could it fly like birds today? A new study published in the Proceedings of the National Academy of Sciences (PNAS) by researchers from China and the U.S. says no. The flight feathers of modern birds are mainly composed of β-keratin, which gives them special biomechanical properties (such as flexibility, elasticity and strength) to meet the needs of flight. Dr. PAN Yanhong from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) and her colleagues used electron microscopy and chemical analyses to compare flight feathers of Anchiornis with those of a chicken and four other feathered dinosaur and fossil birds. They found that Anchiornis feathers were predominated by thicker α-keratins rather than thinner β-keratins, and lacked the biomechanical properties needed for flight, although they did contain some of the necessary molecular structures as indicated by the presence of feather β-keratins. On the other hand, Pan and colleagues also showed that the flight feathers of Chinese Mesozoic birds such as Eoconfuciusornis and Yanornis, as well as a Cenozoic bird, were mainly composed of β-keratins, as in modern birds. The findings suggest that even though Anchiornis feathers were not suitable for powerful flight, their molecular composition may signify an intermediate stage in the evolution of avian flight feathers. Researchers from NIGPAS, the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, Linyi University, North Carolina State University, and South Carolina State University participated in the study. The study was supported by the Chinese Academy of Sciences and the National Natural Science Foundation of China. Reference: Yanhong Pan, Wenxia Zheng, Roger H. Sawyer et al., 2019. The molecular evolution of feathers with direct evidence from fossils. PNAS. DOI: http://doi.org/10.1073/pnas.1815703116. The Anchiornis (STM0-214) specimen studied in this work, collected from Jianchang, western Liaoning, location of samples is marked by red box. A TEM image of the fossilized feather from the Anchiornis specimen, showing the thick filaments composed of α-keratins dominated at the ultrastructural level. Time-scaled evolution of molecular composition and ultrastructure of feathers within a Mesozoic avian and non-avian phylogeny. Filled stars showing the distribution of tested fossil feathers and related integumentary tissues used in this study.
The Fotan Group from Zhangpu of Fujian yielded abundant plant megafossil and amber, generating a typical Miocene tropical rainforest ecosystem of China. The plant fossils are preserved in diatomite and mudstone, while the amber occurs within coal seams and diatomite that directly underlie the layer hosting plant flora. Determining the age of Fotan fossil horizons can help date the Miocene tropical rainforest in China and constrain its long-term history. Recently, Dr. ZHENG Daran and Associate Professor SHI Gongle from the ‘Modern terrestrial ecosystem origin and early evolution’ group at Nanjing institute of Geology and Palaeontology of Chinese Academy of Sciences, cooperating with the researchers from the University of Hong Kong and Columbia University, pioneered this age-determining research and provided a robust 40Ar/39Ar age for the Fotan biota based on the basalt samples from Maping and Wuling of Zhangpu, Fujian Province. For the sample from Maping, incremental heating analysis of groundmass yielded a plateau age of 14.5 ± 1.5 Ma (MSWD = 0.65). Data from the step-heating analysis were plotted on an inverse isochron isotope correlation diagram (36Ar/40Ar vs. 39Ar/40Ar). The isochron age of 15.2 ± 2.0 Ma (MSWD = 1.2) shows well agreement with the plateau age including its error term. For the sample from Wuling, incremental heating analysis of groundmass yielded a well-defined plateau age of 14.7 ± 0.4 Ma (MSWD = 0.28). The isochron age of 14.7 ± 0.4 Ma (MSWD = 0.96) is identical with the plateau age. The 302 ± 2 40Ar/36Ar intercept from the inverse isochron diagram resembles atmospheric values (i.e., 295.5 or 298.56). Although the age results for both samples are indistinguishable at the 2σ level, we interpret the more precise 14.7 ± 0.4 Ma ages as the upper limit of the depositional age of the Fotan fossils. This age constrains interpretations of the early evolution of tropical rainforest ecosystems in Asia, and laid foundation for the systematic study of Zhangpu amber biota. This research was recently published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology, and supported by the National Natural Science Foundation of China and RGC General Research Fund of Hong Kong. Reference: Zheng, D., Shi, G., Hemming, S.R., Zhang, H., Wang, W., Wang, B., Chang, S.-C.*, 2019. Age constraints on a Neogene tropical rainforest in China and its relation to the Middle Miocene Climatic Optimum. Palaeogeography, Palaeoclimatology, Palaeoecology, 518: 82–88. DOI: https://doi.org/10.1016/j.palaeo.2019.01.019. Photograph of a outcrop in Fotan, Zhangpu Stratigraphic column of Fotan Group in Zhnagpu 40Ar/39Ar age result
It is well-known that living fossils exhibit stasis over geologically long time scales. Examples are the panda and ginkgo. Now, two tiny beetles trapped in 99-million-year-old amber may join this group. Beetles are the most species-rich group of animals on our planet. Among four extant suborders of beetles, polyphaga is the largest and most diverse group. The origin and early evolutionary history of polyphagan beetles have been largely based on evidence from the derived and diverse ‘core polyphaga’, whereas little is known about the species-poor basal polyphagan lineages, which include Clambidae and four other extant families. Recently, an international team led by Dr. CAI Chenyang, from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences, reported two new and rare species of the extant family Clambidae from Burmese amber: Acalyptomerus thayerae Cai and Lawrence, 2019, and Sphaerothorax uenoi Cai and Lawrence, 2019. They are important for understanding the early evolution and biogeography of the family and even for polyphagan beetles. Clambidae is a small group of small-sized (usually 0.7–2.0 mm long) polyphagan beetles distributed worldwide, with approximately 150 described species grouped in five extant genera. Most clambid adults occur in decaying vegetation, leaf litter and rotten wood and occasionally fly at dusk. The two new species, represented by five well-preserved fossils, were discovered by Dr. CAI and colleagues from mid-Cretaceous Burmese amber. Both species are extremely morphologically close to their living counterparts, and can be placed in extant genera. Acalyptomerus thayerae (about 1.05–1.15 mm long) has a close affinity to A. herbertfranzi, a species currently occurring in Mesoamerica and northern South America. Sphaerothorax uenoi (about 0.71 mm long) is closely related to extant species of Sphaerothorax, which are usually collected in forests of Nothofagus in Australia, Chile and New Zealand. The discovery of two Cretaceous species from northern Myanmar indicates that both genera had lengthy evolutionary histories, originating at least by the earliest Cenomanian, and were probably more widespread than at present. Remarkable morphological similarities between fossil and living species suggest that both genera changed little over long periods of geological time, which is usually considered to be a feature of living fossils. The long-term persistence of similar mesic microhabitats such as leaf litter may account for the 99-million-year morphological stasis in Acalyptomerus and Sphaerothorax. Reference: Cai C*, Lawrence JF, Yamamoto S, Leschen RAB, Newton AF, Slipinski A, Yin Z, Huang D, Engel MS. 2019. Basal polyphagan beetles in mid-Cretaceous amber from Myanmar: biogeographic implications and long-term morphological stasis. Proc. R. Soc. B, 20182175. DOI:10.1098/rspb.2018.2175 Acalyptomerus thayerae from mid-Cretaceous Burmese amber (Image by NIGPAS) Sphaerothorax uenoi from mid-Cretaceous Burmese amber (Image by NIGPAS) Geographical distribution of Acalyptomerus thayerae and Sphaerothorax uenoi and their related extant counterparts (Image by NIGPAS)
The Cretaceous–Paleogene boundary (K–Pg boundary) marks the beginning of the Cenozoic, and is one of the most important geological boundaries. Charophytes are usually very abundant in the non-marine strata near the K–Pg boundary, and the significant changes of charophyte flora can help to recognize the K–Pg boundary. The “SK-1” scientific drilling project in the Songliao Basin is the first continental Cretaceous scientific drilling under the framework of the International Continental Scientific Drilling Program, which provides a rich source of fossils for this research. Recent investigation conducted by the assistant researcher Sha LI, Professor Qifei WANG, Professor Haichun ZHAMG from “Modern terrestrial ecosystems origin and early evolution research team” at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, cooperated with Xiaoqiao WAN from the China University of Geosciences and Carles MARTíN-CLOSAS from the University of Barcelona, studied the change of charophyte floras from the Cretaceous–Paleogene transition in the Songliao Basin. Four charophyte biozones and one superzone are defined in the Sifangtai and Mingshui formations from the SK-1(North) borehole in the Songliao Basin (NE China) and correlated to the Geomagnetic Polarity Time Scale. These include a mid–late Campanian Atopochara trivolvis ulanensis Zone, a latest Campanian–early Maastrichtian Microchara gobica Zone, a late Maastrichtian Microchara prolixa Zone, and an earliest Danian Peckichara sinuolata Zone. The latter three zones are grouped within the Microchara cristata Superzone, which allows intra- and intercontinental correlation with other basins in China and Europe. Peckichara sinuolata first appears in chron C29r (upper Mingshui Formation) and is proposed as the basal marker of the Paleocene. The biozonation of the K–Pg interval proposed for the Songliao Basin differs from a previous biozonation proposed in the Pingyi Basin since it represents a different biogeographical and palaeoecological context. In the mid-Campanian to Maastrichtian, the flora was limited to freshwater lakes in northern China and Mongolia, whereas in the Pingyi Basin, brackish water dominated. In the Paleocene, the Songliao Basin contained a diverse flora consisting of nine species that thrived in terrigenous and temporary lakes, whereas the flora in the Pingyi Basin was dominated by one species inhabiting permanent alkaline lakes. The species common to the two basins are widely distributed in Eurasia and constitute a useful tool for long-distance correlations, but serve as a less-precise tool for detailed biostratigraphical subdivision within one specific basin. Reference: Li, S.*, Wang, Q.F., Zhang, H.C., Wan, X.Q., Martín-Closas, C.*, 2018. Charophytes from the Cretaceous–Paleocene boundary in the Songliao Basin (north-eastern China): a Chinese biozonation and its calibration to the Geomagnetic Polarity Time Scale. Papers in Palaeontology, DOI: 10.1002/spp1002.1225. Charophytes from the Songliao Basin. Stratigraphic log of the SK-1(N) borehole showing position of samples and of charophytes, calibrated to the GPTS (Deng et al. 2013).
Numerous well-preserved fossils have already been discovered in mid-Cretaceous (late Albian to earliest Cenomanian, ≈100 Ma) amber from northern Myanmar, including new species, genera, and even families of plants and invertebrates. Compared to many new discoveries on insects, researches of the botanical inclusions stay faraway behind, so far only a few derived ferns (polypods) described from the Myanmar ambers. However, the polypod fossils are significant not only in recovering the polypod ferns’ diversity changes in history, but also in bridging the gap between the Cretaceous records of polypod ferns and divergence time estimates obtained based on the DNA sequence variation. For ferns, amber inclusions are scientifically valuable because of their preservation of micro-structures, especially sporangia, which are usually poorly preserved in sedimentary fossils. Two new fern fossils with beautifully preserved sporangia were reported by Prof. LI Chunxiang from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and her colleagues, from the mid-Cretaceous amber of Myanmar. Thyrsopteris cretacea represents the first fossil occurrence of Thyrsopteris in the Myanmar tropical forest. Today only one species is known in Thyrsopteris and Thyrsopteridaceae from temperate southern hemisphere and the new fossil species adds much needed data on the evolutive history of this group of ferns. It adds to the diversity previously ascribed to the Thyrsopteridaceae, which has been based on Eocene fossils, and it extends the fossil record of the family further back to the mid-Cretaceous. Most previous fossils of Thyrsopteridaceae have been from the Southern Hemisphere and are therefore considered Gondwanan. Thyrsopteris cretacea represents one of the few occurrences of the family in Laurasia. Researchers also described another new fossil belonging to the Lindsaeaceae as Proodontosoria myanmarensis gen. et sp. nov.. This new fossil probably scrambled with scandent leaves and spiny axes on other plants. The increasing inventory of the Lindsaeaceae in amber has important implications for the phylogenetic reconstruction of extant Lindsaeaceae lineages and subsequent interpretation of their classification. The morphology of Proodontosoria myanmarensis does not concur with any crown group lineage of Lindsaeaceae, but rather display a character state mosaic of several extant lineages. As a result, the fossil might be a Lindsaeaceae stem group representative, rather than a crown group element. These researches were supported by Project of State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of geology and Palaeontology, CAS) (Grant No. Y626040108), and Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB26000000). References: 1) Chunxiang Li, Robbin C. Moran, Junye Ma, Bo Wang, Jiasheng Hao (2018). A new fossil record of Lindsaeaceae (Polypodiales) from the mid-Cretaceous amber of Myanmar. Cretaceous Research. https://doi.org/10.1016/j.cretres.2018.12.010 2) Chunxiang Li, Robbin C. Moran, Junye Ma, Bo Wang, Jiasheng Hao, Qun Yang (2019). A mid-Cretaceous tree fern of Thyrsopteridaceae (Cyatheales) preserved in Myanmar amber. Cretaceous Research. https://doi.org/10.1016/j.cretres.2019.01.002 Fossil and extant Thyrsopteris. (A–E) Holotype of Thyrsopteris cretacea. (F-I) Extant Thyrsopteris elegans. Proodontosoria myanmarensis gen. et sp. nov. (Lindsaeaceae, Polypodiales).
Silicified and phosphatized microfossils preserved in the Ediacaran Doushantuo Formation in South China provide key evidence for the early radiation of eukaryotes after the Neoproterozoic global glaciations. Two microfossil biozones (the Tianzhushania spinosa biozone from the lower Doushantuo Formation, and the Hocosphaeridium anozos biozone from the upper Doushantuo Formation) have been proposed on the basis of acanthomorphic acritarchs preserved in the Doushantuo Formation chert nodules in the Yangtze Gorges area. However, their correlation with the stratigraphic horizons yielding Weng’an biota, a well-known phosphatized microfossil assemblage, has long been an issue of debate, which hinders our understanding of the radiation pattern of microscopic eukaryotes after the Marinoan glaciation, as well as their biostratigraphic significance in the subdivision and correlation of the Ediacaran successions. OUYANG Qing from Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences and her colleagues carried out litho-, bio-, and chemostratigraphic studies on the Ediacaran Doushantuo Formation in the Zhangcunping area of the western Hubei Province, South China. They found that both the lithostratigraphic sequence and microfossil assemblage at Zhangcunping resemble those at Weng’an, indicating a straightforward correlation between fossiliferous strata in these two areas. Litho- and chemostratigraphic correlations suggest that the microfossil-bearing strata at Zhangcunping could be correlated with the upper part of the lower acritarch biozone in the Yangtze Gorges area, thus supporting the stratigraphic correlation between the stratigraphic units yielding the Weng’an biota at Weng’an and the upper part of the lower acritarch biozone in the Yangtze Gorges area. This correlation scenario supports the idea that the Weng’an biota is biostratigraphically transitional between the lower and upper acritarch biozones, suggesting a stepwise evolutionary pattern of the Ediacaran acanthomorphic acritarchs after the Cryogenian global glaciation, and calls for more detailed investigation on the taxonomical composition and biostratigraphic ranges of acanthomorphs in the T. spinosa biozone in the Yangtze Gorges area, and re-consideration of acanthomorphic biozonation of the Doushantuo Formation in the Yangtze Gorges area. Reference: Ouyang, Q., Zhou, C.*, Xiao, S., Chen, Z., Shao, Y., 2019, Acanthomorphic acritarchs from the Ediacaran Doushantuo Formation at Zhangcunping in South China, with implications for the evolution of early Ediacaran eukaryotes. Precambrian Research, 320: 171–192. Correlation of the Weng’an biota at Weng’an, Guizhou Province and the Zhangcunping microfossil assemblage at Zhangcunping
Some acanthomorphic acritarchs from the Doushantuo Formation at Zhangcunping, Hubei Province, South China
