Some fossil specimens of Austrohamia acanthobractea from the Daohugou biota The Cupressaceae is the only conifer family that distribute in all continents except for Antarctica, and it is especially remarkable for the diversity of morphology, species, and habitat preference exhibited by its members. The fossil record suggests that the ancestral groups of Cupressaceae originated during the Triassic. During the middle-late Mesozoic, the diversity and geographical distribution of Cupressaceae are crucial and the ancestors of all subfamilies appeared and differentiated. However, detailed investigations on morphology and anatomical characteristics of the Mesozoic Cupressaceae taxa are still very limited compared with their rich fossil record, which impede the understanding of the early morphological diversity and evolution of the middle-late Mesozoic Cupressaceae plants. Recently, a research team of the Mesozoic plants represented by Dr. DONG Chong, Prof. WANG Yongdong and Prof. YANG Xiaoju from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS) provide new insight into the whole-plant reconstruction and phylogeny on Austrohamia acanthobractea —a Cupressaceae taxon from the Middle Jurassic Daohugou biota in northeastern China. The study revealed the exquisite details of the vegetative shoots and leaf cuticles, ovulate cones and in situ ovules, pollen cones and in situ pollen grains, providing a complete supplementary depiction on the morphological and anatomical information of this Jurassic cypress plant. The update result was recently published in “International Journal of Plant Science”, a well-known scientific journal published in University Press of Chicago in USA. Whole-plant reconstruction of Austrohamia acanthobractea. Austrohamia, the oldest macrofossil record of Cupressaceae was originally reported from the Early Jurassic in the Argentina of the southern Hemisphere. In addition to the type species, Austrohamia acanthobractea is the second fossil record of the genus. The co-occurrence of Austrohamia in the Jurassic of both the Southern and Northern Hemispheres appears to suggest an intercontinental disjunction between Gondwana and Laurasia. A. acanthobractea is the most common species among the plant fossils from the Daohugou biota. These rich and well-preserved fossil materials with many details makes it to be one of the most completely studied Jurassic Cupressaceae species. In addition, by using the morphological cladistic analysis, the researchers show that the two species of Austrohamia form a polytomy with the expanded Cunninghamioideae clade This supports the original interpretation that the genus is closely related to Cunninghamia and Cunninghamia-like fossils. This study is of great significance for a comprehensive understanding of ancestor groups and diversity of early Cupressaceae. Reconstructed phylogeny for Cupressaceae (left) and figures of bract-scale complexes (right). The Daohugou Lagerstatte is well known for its rich and well-preserved fossil invertebrates, vertebrates and plants, and represents a deposit with some terrestrial elements. In contrast, detailed studies on systematics and diversity in some key plant fossil taxa of this biota is very poorly documented, thus needs more and urgent comprehensively study. This new result by DONG et al. will thus promote and deepen the investigation of key plant fossils in the Daohugou biota. This study was supported by the Strategic Priority Research Program (B) of CAS and the National Natural Science Foundation of China. Reference: Dong, C., Wang, Y. D., Yang, X. J., Sun, B. N., 2018. Whole-Plant Reconstruction and Updated Phylogeny of Austrohamia acanthobractea (Cupressaceae) from the Middle Jurassic of Northeast China. International Journal of Plant Science, 179 (8), 640-662. Doi: 10.1086/699665.
It took less than 30,000 years, and maybe only thousands, to kill more than 90% of sea creatures and most land species, according to the most precise study ever published about the mass extinction marking the end of the Permian Period. A recent study published in the Geological Society of America Bulletin on September 19 suggests an answer.
Outcrop photos of the Permian-Triassic boundary interval at Penglaitan (image by NIGPAS) It took less than 30,000 years, and maybe only thousands, to kill more than 90% of sea creatures and most land species, according to the most precise study ever published about the mass extinction marking the end of the Permian Period. Earth’s greatest mass extinction, also known as the “Great Dying,” occurred about 252 million years ago. By some estimates, over 90% of sea creatures and most land-dwelling reptiles disappeared. Even usually resilient plants and insects suffered near annihilation. But how long did it take to wipe out the vast majority of life on Earth? What could have caused such a massive die-off? A recent study published in the Geological Society of America Bulletin on September 19 suggests an answer. Scientists from China, the USA and Canada combined new high-resolution radiometric dating of seven closely spaced layers of volcanic material from South China’s Penglaitan section with detailed biostratigraphy and geochemical analyses. Results show the duration of the end-Permian mass extinction to be about 31 thousand years, essentially instantaneous by geological standards. “The mass extinction may have occurred in only thousands of years, but the analytical uncertainty of current CA-ID-TIMS dating technique prevents us from getting a more meaningful constraint for less than 30,000 years,” said Prof. SHEN Shuzhong from the Nanjing Institute of Geology and Palaeontology (NIGPAS) of the Chinese Academy of Sciences, the lead author of this paper. Fieldtrip investigation on the Penglaitan section (image by NIGPAS) The study also suggests that the sudden extinction may have been caused by Siberian flood-basalt eruptions, along with local intensive explosive volcanism that may have started some 420 thousand years before the mass extinction. These events may have significantly reduced the stability of Late Permian ecosystems to the point where a single extreme incident finally resulted in a sudden ecosystem collapse. For decades, scientists have studied the Permian-Triassic boundary at Meishan in Zhejiang Province, South China, which serves as the international reference for the boundary. But this “condensed section” – a lot of time represented by a small thickness of sediments – makes it difficult to discern if the extinctions were abrupt or gradual. To deal with this problem, SHEN and colleagues from CAS, MIT, the National Museum of Natural History (Washington, D.C.) and the University of Calgary focused their attention on the Penglaitan section in South China‘s Guangxi Autonomous Region. The Penglaitan sediments were deposited in shallow, tropical waters where sediments accumulated more than 100 times faster than in the Meishan beds, making the Penglaitan sediment much thicker than Meishan for a comparable period of time. In other words, only a few centimeters of rock at Meishan are equivalent to meters of sediment in Penglaitan. The expanded section at Penglaitan allowed the scientists to study the events at the Permian-Triassic boundary at a much higher temporal resolution. In addition to the higher sedimentation rates, the Penglaitan section has better geochronologic and stratigraphic controls, and rich palaeontological data, enabling examination of the fine structure of the extinction and coeval environmental perturbations. SHEN and his colleagues documented a rich Late Permian biota at Penglaitan, with at least 10 major marine fossil groups, including brachiopods, ammonoids, sponges, corals, conodonts, foraminifera, bryozoans, bivalves, and trilobites. Twenty-nine of the 66 Permian species identified in the section disappeared within or at the top of a single bed of volcanic ash-rich sandstone (Bed 141). Moreover, there is no “survival interval” of Permian taxa extending into the Early Triassic. This highly diverse marine ecosystem suddenly disappeared during the time of deposition of Bed 141. The radiometric ages of the Siberian Traps volcanism match the radiometric dates recovered from the volcanic ash beds preserved at Penglaitan and Meishan. The overlap in dates suggests that the environmental effects of volcanic gases like carbon dioxide, methane and sulfur dioxide could have been deadly. A lethal greenhouse warming, oceans depleted of dissolved oxygen, acid rain, and atmospheric pollution by heavy metals would have made life difficult. Detailed fossil ranges and conodont zones in the uppermost Changhsingian and lowermost Triassic of the Penglaitan section and their correlation with the extinction and survival interval of the Meishan section (image by NIGPAS) Previously, scientists working on the problem were not even sure whether there was one pulse or two pulses of extinction at the Permian-Triassic boundary, or whether some Permian species actually survived into the earliest Triassic beds. These problems could not be resolved in condensed sections like Meishan. In contrast, the Permian deposits at Penglaitan contain more than 50 volcanic ash layers and volcanic ash-rich sandstone beds, possibly produced by pyroclastic flows from the nearby volcanic arc eruption centers in South China, thus presenting a clearer picture of the extinction period. The abrupt change in deposition from the uppermost Permian limestones and ash-rich sandstones to black shale with centimeter-scale limestone interbeds in the lowermost Triassic clearly represents a major shift in the oceanic environment. The Permian extinction has in the past been linked to a time of rapid climate warming, potentially produced by carbon dioxide and methane emissions from the massive Siberian flood basalt eruptions. High-resolution paleotemperature measurements across the mass extinction interval suggest a substantial warming of up to 10 degrees Celsius immediately after the mass extinction event. “This might explain the shift in sediment type from limestones in the Permian to early Triassic black shales, indicating ocean anoxia,” said SHEN. A warming climate may cause ocean currents to become sluggish while at the same time bringing increased nutrients into the sea from increased weathering and river runoff. The reduction in mixing of oxygen-rich waters from the ocean surface with deeper waters, and the increase in ocean productivity triggered by the increased nutrient supply, could have led to increased organic carbon deposition and resulting ocean anoxia. Related article: SHEN, S.-Z., Ramezani, J., Chen, J., Cao, C.-Q., Erwin, D.H., Zhang, H., Xiang, L., Schoepfer, S.D., Henderson, C.M., Zheng, Q.-F., Bowring, S.A., Wang, Y., Li, X.-H., Wang, X.-D., Yuan, D.-X., Zhang, Y.-C., Mu, L., Wang, J., and Wu, Y.-S., 2018, A sudden end-Permian mass extinction in South China: GSA Bulletin, https://doi.org/10.1130/B31909.1.
Insect pollination played an important role in the evolution of angiosperms. Recently, a research group provide new insight into the niche diversity, chemical communication, and defence mechanisms of Mesozoic pollinating insects. This research was recently published in Nature Communications on September 17th, 2018. Ecological restoration of kalligrammatids. a, Jurassic kalligrammatids in the Daohugou forest. b, Cretaceous kalligrammatids in the Burmese amber forest (image by YANG Dinghua) Romeo and Juliet, a romantic but sentimental love story happened in Italy. Now there is a more ancient version, which happened between gymnosperm and pollinating lacewings described as “butterflies of the Jurassic”. Insect pollination played an important role in the evolution of angiosperms. Little is known, however, about ancient pollination insects and their niche diversity during the pre-angiosperm period due to the rarity of fossil evidence of plant–pollinator interactions. Recently, a research group led by Prof. WANG Bo from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) provide new insight into the niche diversity, chemical communication, and defence mechanisms of Mesozoic pollinating insects. This research was recently published in Nature Communications on September 17th, 2018. One of the most intensely investigated examples of pollination niches is the morphological match between the insect proboscis and floral tube length originated from Darwin’s publication in 1877. Kalligrammatid lacewings are among the largest and most conspicuous Mesozoic insects with siphoning mouthparts. The researchers from NIGPAS reported 27 well-preserved kalligrammatids from late Cretaceous Burmese amber (99 million years ago) and Chinese Early Cretaceous (125 million years ago) and Middle Jurassic (165 million years ago) compression rocks. Jurassic and Cretaceous kalligrammatids from China. The lengths of kalligrammatid proboscides vary greatly, from 0.6 to 3.2 mm in amber inclusions and from approximately 5 to 18 mm in compression fossils. The high diversity of kalligrammatids and large variation in their proboscis lengths strongly suggest diverse plant hosts with different floral tube lengths and pollination niche partitioning may have been present among some Mesozoic insects. If pollination niches were partitioned, as in extant ecosystems, this likely increased pollination effectiveness and reduced costs in pollination mutualisms, thus contributing to the high diversity of pollinating insects and the success of pollinator-dependent plants during the Cretaceous period. Kalligrammatid species diversification was potentially promoted by coevolution between pollinating kalligrammatids and their host plants under highly partitioned pollination niches. Traits such as wing eyespots, which likely functioned as a defence in large-sized species, and sexually dimorphic antennae, which were likely used for pre-mating chemical communication, elucidate how kalligrammatids survived in the Mesozoic terrestrial ecosystem under intense competition. However, such elaborate associations between kalligrammatids and their host plants (mostly confined to gymnosperms) could have been a main factor contributing to the extinction of kalligrammatids, which likely occurred during the late Cretaceous with the decline in gymnosperm diversity. Reference: Liu Qing, Lu Xiumei, Zhang Qingqing, Chen Jun, Zheng Xiaoting, Zhang Weiwei, Liu Xingyue*, Wang Bo* (2018) High niche diversity in Mesozoic pollinating lacewings. Nature Communications, 9: 3793. DOI:10.1038/s41467-018-06120-5
Scientists from China and the UK reported two Middle-Late Triassic entomofaunas, providing not only the earliest records of several modern insect elements, but also new insights into the early evolution of freshwater ecosystems.This study confirms that holometabolous and aquatic insects experienced extraordinary diversification about 237 million years ago. The research was published in Science Advances on September 5, 2018. Photographs of typical insect fossils from Tongchuan and Karamay entomofaunas (Image by NIGPAS) Recently, scientists from China and the UK reported two Middle-Late Triassic entomofaunas, providing not only the earliest records of several modern insect elements, but also new insights into the early evolution of freshwater ecosystems. This study confirms that holometabolous and aquatic insects experienced extraordinary diversification about 237 million years ago. The research was published in Science Advances on September 5, 2018. Dr. ZHENG Daran and Prof. WANG Bo, researchers at the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences, discovered a late Ladinian Tongchuan entomofauna and a Carnian Karamay entomofauna in northwestern China. These entomofaunas provide new evidence for understanding the process of insect diversification. The Tongchuan entomofauna contains at least 28 insect families in 11 orders, making it among the most diverse Triassic entomofaunas. The Karamay entomofauna comprises 10 insect families in six orders, including caddisfly cases and the earliest known water boatmen. The Tongchuan entomofauna includes are diverse fossil beetles with bodies, making them potential key calibration points for the molecular phylogenetic analysis of beetle phylogeny. Another interesting discovery is the earliest caddisfly cases (Trichoptera) in both entomofaunas. The true Trichoptera was thought to have diverged from Amphiesmenoptera in the earliest Jurassic. The Holometabola are the most diverse insects in the Tongchuan and Karamay entomofaunas and are represented by diverse beetles and scorpionflies. Holometabola were thought to have become dominant in the global entomofauna starting in the mid-Mesozoic. Thus, its high diversity and abundance in Tongchuan and Karamay are relatively unexpected, revealing a radiation of Holometabola during the Middle Triassic. In addition, water boatmen are abundant in the Karamay entomofauna, making them the earliest record of aquatic bugs. These aquatic insects developed new herbivore and carnivore guilds that persist to the present. The diversification of aquatic insects was thought to be part of the “Mesozoic Lacustrine Revolution,” which dates to the Middle Mesozoic. The current study suggests, however, that this diversification had already begun by the Middle Triassic, thus providing new insights into the early evolution of freshwater ecosystems. Compared to other insects, Holometabola were probably more resilient to Early Triassic environmental disturbances, since their development would have allowed greater buffering from environmental variability. After the Early Triassic, various plants started to appear during the Middle Triassic and spread later, probably further contributing to the radiation of holometabolous and aquatic insects. Reference: Zheng Daran, Chang Su-Chin*, Wang He, Wang Jun, Feng Chongqing, Xie Guwei, Fang Yan, Zhang Haichun, Wang Bo* (2018) Middle-Late Triassic insect radiation revealed by diverse fossils and isotopic ages from China. Science Advances, 4: eaat1380. doi:10.1126/sciadv.aat1380.
Late Ordovocian paleogeography, showing similarity between equatorial position of South China plate to that of modern Galápagos Islands. The eastern equatorial Pacific cold tongue plays a vital influence on ocean-atmasphere CO2 exchange global climate patterns. Recently, a team from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and Western University, Canada reported an equatorial cold-water tongue in the Late Ordovician on the basis of the evidence from paleontological, sedimentological and geochemical data. This research will be published on Geology lately. Recent paleogeographic reconstructions place the South China plate in paleoequatorial latitudes during the Late Ordovician. The northward drift of South China has been extrapolated based on paleomagnetic data, which point to a southern subtropical position in the Early Ordovician and equatorial latitudes by the mid-Silurian. This paleogeographic reconstruction, however, apparently contradicts sedimentary, faunal, and newly acquired δ18Oconodont-apatite data, which show an overall change from Early Ordovician warm water to Late Ordovician cool-water depositional environments. During the Early Ordovician, the carbonate facies of the Yangtze Platform have shallow and warm water characteristics, such as oolites of the Nantsinkuan and Fenghsiang Formations and Calathihum calcareous sponge reefs of the Hunghuayuan Formation. The brachiopod fauna is also characterized by the water-water taxa, such as Sinorthis, Finkelburgia and Tritoechia during the Early and early Middle Ordovician. In contrast, the Upper Ordovician sedimentary facies sedimentary facies and the benthic shelly faunas on the Yangtze Platform have characteristics of a cool-water origin. In the Upper Ordovician, the cool and deep-water Foliomena brachiopod fauna prevailed on the Yangtze Platform. Furthermore, a new stable-oxygen-isotopic curve, based on conodont apatite from the Ordovician succession of Yangtze Platform, shows an overall cooling trend through the Ordovician, implying a broad transition from a warm-water to a cool-water tropical environment, in contrast to the northward drift of South China from subtropical to equatorial latitude from Early to Late Ordovician. In the Ordovician, the long coastline of Gondwana had a geographic setting similar to that of modern Antarctica-South America. The vast Gondwana land mass was centered on the South Pole. With continued global cooling during the Late Ordovician and onset of the continental ice cap, the cold water along high-latitude Gondwana likely generated deep or intermediate flows, as well as surface cold currents similar to the modern Humboldt Current, bringing nutrient-laden cool waters to the shallow ocean surface to form the Cold Tongue. In addition, South China during the Late Ordovician was similar to the Galápagos Islands today in their position within an equatorial cold tongue. This paleogeographic setting would have promoted cool-water upwelling to promote high primary productivity, episodic eutrophication, and organic-rich deposits. This research was supported by the National Natural Science Foundation of China, the Strategic Priority Research Program of the Chinese Academy of Sciences, the Natural Science and Engineering Research Council of Canada. Reference: Jin, J.S., Zhan, R.B. & Wu, R.C. 2018. Equatorial cold-water tongue in the Late Ordovician. Geology. https://doi.org/10.1130/G45302.1
An international team found fossil Myrmeleontiformia fauna from mid-Cretaceous (approximately 100 million years ago) Burmese amber. Their findings show that Myrmeleontiformia did not gain considerable morphological novelty during the subsequent 100 million years, and their diversity seemed to result from different combinations of a limited set of character traits in a complex trade-off.
Reconstruction of two lacewing larvae (Image by YANG Dinghua) Myrmeleontiformia (antlions and their relatives) are an ancient group of lacewing insects characterized by predatory larvae with unusual morphologies and behaviors. An international team led by Prof. WANG Bo from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) and two Italian researchers found fossil Myrmeleontiformia fauna from mid-Cretaceous (approximately 100 million years ago) Burmese amber. The study was published in Nature Communications on August 22, 2018. Their findings show that Myrmeleontiformia did not gain considerable morphological novelty during the subsequent 100 million years, and their diversity seemed to result from different combinations of a limited set of character traits in a complex trade-off. This morphological stasis helped in reconstructing behaviors not preserved by a trace in the fossil record. Inference of these behaviors shed light on the ecological niche and lifestyle of extinct Myrmeleontiformia. Statistical correlation analysis strongly supported a correlation between a selection of morphological traits and two hunting strategies of these ambush predators – camouflaging and fossoriality – allowing us to reconstruct habits of extinct species. The findings suggested that fossorial specializations evolved more than once across Myrmeleontiformia from arboreal ancestors. The fossorial lifestyle of antlions was certainly one of the factors leading to their success, allowing these insects to colonize and diversify in arid habitats where they survived considerable changes in terrestrial environments during the Cretaceous lineages.
Diversity of lacewing larvae in mid-Cretaceous Burmese amber. The Burmese fossils showed that debris-carrying characterized this lineage for at least 100 million years. All of these camouflaging lacewings were equipped with elongate protuberances. The strong statistical correlation between the presence of these protuberances and camouflaging behavior demonstrated that this trait is an indicator of such behavior, even when the debris covering is not directly preserved in the amber piece together with the larvae. This research also implies that camouflaging behavior arose at least three times within Myrmeleontiformia. Camouflaging and fossoriality appear widespread across the lineage, and both behaviors allowed the predatory larvae to hide from their unsuspecting prey. Reference: Badano D.*, Engel M.S., Basso A., Wang Bo*, Cerretti P.* (2018) Diverse Cretaceous larvae reveal the evolutionary and behavioural history of antlions and lacewings. Nature Communications, DOI: 10.1038/s41467-018-05484-y
Plant-insect interactions form one of the critical bedrocks for modern ecosystems, either as pollination associations or relating to herbivory. A new mid-Cretaceous (99-million-year-old) boganiid beetle with specialized pollen feeding adaptations was reported in Current Biology on August 16, 2018. This suggests an ancient origin of beetle pollination of cycads long before the rise of flowering plants. Cycad pollen grains associated with C. cycadophilus (Image by NIGPAS) Plant-insect interactions form one of the critical bedrocks for modern ecosystems, either as pollination associations or relating to herbivory. A new mid-Cretaceous (99-million-year-old) boganiid beetle with specialized pollen feeding adaptations was reported in Current Biology on August 16, 2018. This suggests an ancient origin of beetle pollination of cycads long before the rise of flowering plants. Plant-insect interactions are largely dominated by insect-angiosperm relationships owing to the hegemony enjoyed by flowering plants since the Late Cretaceous. Gymnosperm-insect interactions, on the other hand, are far less known, particularly in terms of pollination modes. Nonetheless, insect-mediated pollination in gymnosperms and potentially prior to the rise of flowering plants is critical for understanding not only the complex biology of these plants today but also the ecology of pre-angiospermous ecosystems and the history of pollination specializations on gymnosperms. Phylogenetic analyses of the beetle and associated pollen grains conducted by Dr. CAI Chenyang from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and colleagues indicate that it was probably a pollinator of early cycads. Unlike modern wind-pollinated conifers and Ginkgo, cycads are unusual in that they are an ancient group of gymnosperms pollinated by insects, such as beetles and rarely thrips. Little is known about the early evolution of their pollination mode before the rise of angiosperms, or flowering plants, although cycads are well documented from the mid-Mesozoic. The researchers discovered a new genus and species of boganiid beetle, named Cretoparacucujus cycadophilus Cai and Escalona, 2018, preserved with many tiny cycad pollen grains and possessing specialized mandibular patches for the transport of cycad pollen. Most importantly, morphology-based phylogenetic placement of the species reveals it belongs to a clade of relict surviving genera with a disjunct distribution encompassing southeastern Africa and southwestern Australia who are also specialist pollinators of the same clade of modern cycads. Thus, both morphological and phylogenetic evidence support the determination of the fossil as a cycad-associated insect species. Ecological reconstruction of the mid-Cretaceous C. cycadophilus (Image by NIGPAS) The fossil represents the earliest definitive fossil evidence for cycad-insect interactions, and illuminates the ancient history of the establishment of complex entomophily in cycads. It also indicates a probable ancient origin of beetle pollination of cycads at least in the early stage of the Jurassic, some 176 million years ago, long before flowering-plant dominance and the radiation of their pollinators such as bees and butterflies later in the Cretaceous. This research was supported by the National Natural Science Foundation of China, the Strategic Priority Research Program (B) of the Chinese Academy of Sciences, and the Natural Science Foundation of Jiangsu province. Reference: Chenyang Cai*, Hermes E. Escalona, Liqin Li, Ziwei Yin, Diying Huang, Michael S. Engel (2018) Beetle pollination of cycads in the Mesozoic. Current Biology, DOI: 10.1016/j.cub.2018.06.036
In the past years, research groups from NIGP, Chinese Academy of Sciences have made detailed investigations for the amber sites in Myanmar. Recently, one of the groups found a new amber biota—Tilin amber biota (~72 .1Ma) from Tilin, Gangaw district, Magway region of central Myanmar. This research was published in Nature Communications on August 9, 2018.
In the past ten years, many important discoveries have been reported from Burmese amber. The well-known Burmese amber, also called Kachin amber, was from Kachin area of north Myanmar, with a geological age of ~98.8 Ma. However, very few geological investigations has been carried out for Kachin amber due to various reasons. In the past years, Dr. ZHWNG Daran and Prof. WANG Bo from the ‘Modern terrestrial ecosystem origin and early evolution’ group of Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences have made detailed investigations for the amber sites in Myanmar. Recently, this group cooperated with researchers from Hong Kong, England, France and India found a new amber biota—Tilin amber biota (~72 .1Ma) from Tilin, Gangaw district, Magway region of central Myanmar. This research was published in Nature Communications on August 9, 2018.
Geology of Tilin amber In Tilin, more than 30 pits distribute along the hill baron and a typical pit is generally 1 m wide and 10–20 m deep to reach amber-bearing layers. The amber samples are preserved in coal seams beneath a grey tuff and above a yellow sandstone intercalated by conglomerates near mine surface. One tuff sample was collected just above the amber-bearing layers for LA-MC-ICP-MS U-Pb dating. Most zircon grains separated from tuff exhibited euhedral morphologies and oscillatory zoning patterns, indicating an igneous origin and no obvious sedimentary transport. A total of 15 zircons (concordance > 98%) were analyzed. Ten analyses provide the youngest age at 72.1 ± 0.3 Ma (MSWD = 0.6), which is near the Campanian-Maastrichtian boundary, and indicates a latest Campanian age for the underlying amber-bearing layers. Besides, some ammonites were found preserved in nodules of brown sandstone underlying the amber layer. They belong to the genus Sphenodiscus, which was considered to be originated from Campanian and restricted to the Maastrichtian, providing a late Campanian to Maastrichtian lower constraint for Tilin amber. Together with the radio-isotopic age for the upper constraint, Tilin amber should be within the latest Campanian age. As such, Tilin amber is at least 27 million years younger than Kachin amber.
Photograph of Tilin amber outcrop The Tilin amber fragments were analyzed using Pyrolysis Gas Chromatography Mass Spectrometry (Py-GC-MS). Tilin amber is diagenetically altered, with diagnostic biomarkers degraded. The major pyrolysis products are aromatic compounds clearly indicating a gymnosperm origin. Although Tilin was close to Kachin in West Burma block during Cretaceous, Tilin amber is chemically clearly distinct from Kachin amber, which supposedly originated from araucarian or pinaceous trees. Angiosperms explosively diversified in mid-Cretaceous time, and became dominant in forests worldwide by the Maastrichtian. However, the gymnosperm-derived Tilin amber suggests that gymnosperms were still abundant in the latest Campanian equatorial forests. Nowadays, the forests of Southeast Asia are dominated by dipterocarps (Dipterocarpaceae, a family of angiosperm), and dipterocarp fossils and resins are present in India and Southeast Asia by the Eocene. As such, the replacement of gymnosperms by dipterocarps in Southeast Asian forests most likely occurred from the Maastrichtian to Paleocene.
U-Pb geochronology for Tilin amber Tilin amber is frequently translucent and reddish or yellowish in color. The amber pieces are usually small and seldom longer than 10 cm. A total of 52 arthropod and plant inclusions were found in 5 kg of amber. The insect fauna is composed of 12 families of eight orders, including Hymenoptera, Diptera, Hemiptera, Psocoptera, Coleoptera, Blattaria, Mantodea, and Neuroptera, and is dominated by Hymenoptera and Diptera (80% of all insects). A notable discovery is six worker ants belonging to three unknown genera of the extant subfamily Dolichoderinae, as well as a dealate female likely of the Ponerinae. The ants from Tilin amber are one of the earliest records of crown group ants, as only two Cretaceous species have been definitively assigned to extant subfamilies until now. All other ants recorded earlier in the Cretaceous belong to extinct subfamilies. Our findings provide reliable evidence for the Late Cretaceous radiation of crown group ants, and the apparent absence of sphecomyrmines suggests that the turnover from stem-groups to crown groups had already begun by the latest Campanian.
Fig. 4 Photographs of ants in Tilin amber Despite the large number of Cretaceous and Cenozoic insect faunas to date, there is a 24-million-year gap spanning from the early Campanian to the early Eocene, which dramatically hinders our understanding of the reorganization of terrestrial ecosystem and the impact of the K-Pg extinction event on the evolution of insects. Tilin amber biota yields the latest known diverse insect assemblage in the Mesozoic, and provides a unique window into a vanished tropical forest. The age, chemical components, and inclusions of Tilin amber are different from those of Kachin amber in northern Myanmar, showing a biotic change from mid-Cretaceous to Late Cretaceous. This research was supported by the National Natural Science Foundation of China, the Strategic Priority Research Program (B) of the Chinese Academy of Sciences, and the HKU Seed Funding Program for Basic Research, Reference: Zheng Daran, Chang Su-Chin*, Perrichot V., Dutta S., Rudra A., Mu Lin, Kelly R.S., Li Sha, Zhang Qi, Zhang Qingqing, Wang Jun, Wang He, Fang Yan, Zhang Haichun, Wang Bo * (2018). A Late Cretaceous amber biota from central Myanmar. Nature Communications, DOI: 10.1038/s41467-018-05650-2.
We are currently living in an icehouse world with continental glaciation in Earth’s poles that initiated at ~34 Ma. The Late Palaeozoic Ice Age (LPIA, ~340–285 Ma) is one of two major icehouses of the Phanerozoic and records the only greenhouse gas forced transition from an icehouse with complex terrestrial ecosystems to a fully greenhouse world. It was a time of low atmospheric pCO2 and high pO2, comparable to Today’s atmospheric composition, formation of the supercontinent Pangaea, dynamic glaciation in the Southern Hemisphere, and radiation of the oldest tropical rainforests. Although it has been long appreciated that these major tectonic, climatic, and biotic events left their signature on seawater 87Sr/86Sr through their influence on Sr fluxes to the ocean, the temporal resolution and precision of the Late Palaeozoic seawater 87Sr/86Sr record remain relatively low. Recently, a new study by a team from NIGPAS and University of California–Davis presents a high-temporal-resolution and high-fidelity record of Carboniferous–early Permian seawater 87Sr/86Sr based on conodont bioapatite from an open-water carbonate slope succession in South China. The new data define a rate of long-term rise in 87Sr/86Sr (0.000035/m.y.) from ca. 334–318 Ma comparable to that of the middle to late Cenozoic. The onset of the rapid decline in 87Sr/86Sr (0.000043/m.y.), following a prolonged plateau (318–303 Ma), is constrained to ca. 303 Ma. A major decoupling of 87Sr/86Sr and pCO2 during 303–297 Ma, coincident with the Palaeozoic peak in pO2, widespread low-latitude aridification, and demise of the pan-tropical wetland forests, suggests a major shift in the dominant influence on pCO2 from continental weathering and organic carbon sequestration (as coals) on land to organic carbon burial in the ocean. The new Sr data also provide an important tool for precise stratigraphic correlation of the Carboniferous successions worldwide, which is critical to the “GSSP” works on the four Carboniferous stages. Reference: Jitao Chen*, Isabel P. Monta？ez, Yuping Qi, Shuzhong Shen, Xiangdong Wang, 2018. Strontium and carbon isotopic evidence for decoupling of pCO2 from continental weathering at the apex of the late Paleozoic glaciation. Geology, 46, 395–398. DOI:10.1130/G40093.1.
Discoveries of animal embryos have profoundly improved our understanding of the early evolution of animal development. However, the fossil record of early animal embryos is extremely rare. Recently, a team from NIGPAS and University of Southern California discovered some three-dimensionally (3-D) phosphatized animal embryos called “Archaeooides” from the basal Cambrian (about 535 million years ago) in southern Shaanxi Province, China. This research was published in Geology as a cover paper in this May. In order to reveal the morphology and internal structures of these Archaeooides fossils, the researchers applied advanced high-resolution X-ray microscopic tomography to produce 3-D reconstructions of a number of specimens. And the high quality dataset they got demonstrates that these soft-bodied fossil organisms have a thick cyst characterized by pustule-like ornaments and vesicular structures. Furthermore, a multicellular inner body undergoing palintomic cell division is enclosed by the cyst. The suite of characters, including submillimeter to millimeter scale, a palintomic pattern of cell division, and a complex cyst wall microstructure, corroborate the hypothesis that Archaeooides fossils represent the embryonic remains of animals. More specifically, the structure of the cyst wall bears close comparison to the resting cysts of living invertebrates, allowing the research to interpret Archaeooides as a diapause embryonic stage. Like the extant invertebrate diapause embryos which can survived in harsh environmental conditions, Archaeooides evolved thick, porous cyst to adapt to the temporally and spatially heterogeneous redox conditions that likely extended from the Ediacaran to the early Cambrian. The global distribution of fossil Archaeooides indicates that these environmental conditions were geographically widespread. In the light of this research, Archaeooides provides evidence of the early evolution of this metazoan life history strategy as an adaptation to adverse environmental conditions. Its widespread occurrence in both conventional and exceptional taphonomic windows provides the potential for reconstructing its embryology and, by inference, the developmental evolution of early animals and their body plans. Reference: Zongjun Yin, Duoduo Zhao, Bing Pan, Fangchen Zhao, Han Zeng, Guoxiang Li, David J. Bottjer, and Maoyan Zhu. Early Cambrian animal diapause embryos revealed by X-ray tomography. Geology, 2018.
