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This work aims to study the preserved communities in rocks from the Cambrian-Ordovician, exposed west of the Arivechi, Sonora town in northwest Mexico. A total of 860 individuals from 70 species are analyzed, belonging to four Cambrian units (El Gavilán, El Mogallón, Milpillas, and La Huerta formations) and one Ordovician unit (El Santísimo formation), the latter one divided into three members. After a petrographic and paleoecological analysis, it is concluded that the El Gavilán and El Mogallón formations are characterized by deposits of an open and external platform dominated by epifaunal suspension feeders. The Milpillas formation is distinguished by rocks deposited in an open and restricted internal platform environment, where epifaunal organisms and suspension feeders prevail. The La Huerta formation is notable for its high content of brachiopods, epifaunal organisms, and suspension feeders. The first two members of the El Santísimo formation show a significant environmental change, as they are deposits from a deep-water cratonic basin. The change in biota includes planktonic organisms and suspension feeders. Finally, the upper member of the El Santísimo formation contains biota characteristics of a slope and a shallow marine platform environment near the coastline, with abundant nektobenthic organism life. • A paleoecological study is performed for the Cambrian-Ordovician of Arivechi, Sonora. • Cambrian-Ordovician marine communities are dominated by sessile organisms. • Faunal assemblage has affinity with Laurentia. [ABSTRACT FROM AUTHOR]

The significant changes in seafloor conditions during the Ediacaran-Cambrian transition presumably bear on the autecology of the benthic animals living in this time interval. However, little evidence shows morphological modifications and life strategy transitions in early animals in response to this substrate revolution. Dinomischidae is a family of diploblastic-grade with a sessile, suspension-feeding lifestyle, which includes Xianguangia , Daihua and Dinomischus. Here, we redescribe Calathites spinalis , a poorly known taxon from the early Cambrian (Epoch 2, Age 3, ∼518 Ma), as a new member of this family. Our new material reveals that the body of C. spinalis consists of a stalked calyx and 18 tentacle-sheath complexes, which is a typical trait of dinomischids. Our phylogenetic analyses recover Calathites as a sister group of Xianguangia and Daihua and support dinomischids being a monophyletic group. Members of dinomischids possess unique attachment structures that vary in shape and size, presenting a unique example of morphological adaptations of early sessile animals during the Cambrian substrate revolution. Comparison with early metazoan fossils reveals that dinomischids and other early basal metazoans lagged behind sessile bilaterians in terms of adaptations to substrate changes; the former tends to persist with attachment strategies adapted to Proterozoic-style seafloor conditions that were relatively firm. [Display omitted] • Exquisite fossils of Calathites exhibit traits typical of dinomischids. • Dinomischids have diverse types of attachment structures. • Dinomischids are categorized as shallow sediment stickers adapted to firm Proterozoic-style seafloor conditions. • Insights into adaptations of Chengjiang sessile metazoans to the Cambrian substrate revolution. [ABSTRACT FROM AUTHOR]

The role of environmental change as a significant force driving biological evolution during the Ediacaran–Cambrian transition remains a subject of extensive debate. In this study, we present high-resolution C-isotope data of organic matter (δ13C org) and multiple S-isotope compositions of pyrite (δ34S py and Δ33S py) obtained from a continuous drill core (ZK1505) in South China, spanning the interval from the Ediacaran to Cambrian Stage 2. Our δ13C org and δ34S py data, combined with published data from four sections deposited across a shelf-to-basin transect, reveal substantial gradient from shallow to deep water in δ13C org and sustained positive δ34S py values in the early Cambrian. The vertical δ13C org gradient suggests chemical stratification of the early Cambrian ocean, characterized by oxic shallow water and anoxic deep water. The sustained positive δ34S py values in the same period suggest low seawater sulfate concentrations. Furthermore, we observed intermittent occurrences of negative Δ33S py values coupled with positive δ34S py , suggesting a dominant deep-water anoxia during early Cambrian in the Yangtze Block. We propose that protracted deep-water anoxia may have contributed to the extinction of the Ediacaran biota and played a significant role in the evolution of Cambrian animals. • Vertical δ13C org gradient reveals chemical stratification of the early Cambrian ocean. • Positive δ34S py may have resulted from low seawater sulfate concentrations in the early Cambrian ocean. • Negative Δ33S py coupled with positive δ34S py suggests a dominant deep-water anoxia. • Deep-water anoxia may have hindered the flourishing of early Cambrian animals on the seafloor. [ABSTRACT FROM AUTHOR]

• Iron-speciation data obtained from Ediacaran black shales of 14 sections in the Yangtze block are compiled. • General ferruginous states with localized euxinic zones and widespread euxinic settings are detected in the early and middle Ediacaran ocean of the Yangtze block, respectively. • RSEs concentrations of black shales are apparently higher in the Member IV shales than in the Member II shales of the Doushantuo Formation. • TOC contents in the Doushantuo black shales display apparent relevance to the spatial distribution of euxinic rather than ferruginous states. • Sulfurization process may play favorable roles in burial and preservation of organic matters. Early to middle Ediacaran organic-rich black shales host several famous fossil biotas and provide key evidence for understanding the coevolution of multicellular organisms and palaeoceanic environment. The water column redox states play critical roles in organic-rich shale deposition. Amongst multiple geochemical redox indexes, iron-speciation chemistry (Fe HR /Fe T , Fe py /Fe HR) in shales constitutes a reliable proxy to reconstruct the first-order redox framework of the ocean basin. However, iron-speciation is a local marine redox proxy, and only compiled data collected from multiple different sedimentary facies record statistically significant changes of oxidation states within a depositional basin. Here we compiled the spatiotemporal distribution of iron-speciation data in early to middle Ediacaran black shales of the Yangtze block in South China. New high-resolution analysis on two outcrops and one drill-core reflects overall ferruginous condition and dominant euxinic condition locally interrupted by oxic states, respectively, generally indicating pervasive anoxic depositional environment for the Member II shales of the Ediacaran Doushantuo Formation in the Lower Yangtze block. Compilation of fourteen Ediacaran sections from shallow-, slope- and deep-water facies demonstrates frequent spatiotemporal oscillation of the redox conditions throughout the Yangtze block. Widespread ferruginous states, accompanied with euxinic zones mainly focusing in lower slope facies, are detected during the early Ediacaran period, in contrast with more widespread euxinic settings in the middle Ediacaran period. Statistical data including new high-resolution results from the Lower Yangtze block show generally low enrichment for redox sensitive elements (RSEs, e.g., Mo, V and U) in the Member II shales probably due to their contemporary low seawater concentrations. An increase of RSEs concentrations occurs in the Member IV shales, which probably reflects more oxidized Earth surface environment during middle Ediacaran period. The increasing Earth oxygenation documents the occurrence of widespread euxinic states during deposition of the Member IV shales. Compilation of spatial distribution of TOC contents in black shales demonstrates their apparent relevance to spatial distribution of the euxinic rather than ferruginous states, which is likely due to the favorable role of sulfurization process on burial and preservation of organic matters. The euxinic states may also facilitate the exceptional preservation of the soft-bodied Ediacaran fossils. [ABSTRACT FROM AUTHOR]

The oldest evidence of motile complex benthic multicellular organisms is found in Ediacaran aged rocks. At Nilpena Ediacara National Park (NENP), South Australia, one of the most iconic of such organisms, Dickinsonia, are found in abundance, with over 500 individuals preserved across the site's 33 in situ, fossiliferous beds. These beds vary in mat type and maturity, community diversity and population size. Here, we investigate six beds using spatial point pattern analysis (SPPA) to compare Dickinsonia spatial distributions between populations. Five populations were best-fit to a completely spatially random pattern, with a single outlier (TC-MM3) exhibiting signs of environmental heterogeneity. When distributions were examined in relation to other taxa, no indication of spatial competition was detected. Univariate and bivariate spatial distributions imply that Dickinsonia was generally not impacted by competition with other taxa, meter-scale environmental heterogeneity, or other external factors. These patterns hold when analyses were split between populations of large and small individuals, and these two size cohorts had no measurable effect on each other's spatial distributions. Additionally, we find no indication of intraspecific competition for Dickinsonia or any change in the preferred resources or habitats with growth. These results suggest that the anactualistic environmental conditions produced by ubiquitous organic mats present across Ediacaran seafloors at NENP provided such abundant nutrients that Dickinsonia did not have to compete for resources at the meter scale. These results further inform community-scale dynamics of Earth's earliest complex ecosystem. • Dickinsonia • Abundant resources in the Ediacaran promoted random and independent distributions. • Ongoing research at Nilpena Ediacara National Park, South Australia. • Applied spatial point pattern analysis. • Motile organisms' interactions with Ediacaran ecosystems. [ABSTRACT FROM AUTHOR]

The Neoproterozoic–Cambrian transition was a key period in Earth's history, particularly because changes in the oceanic redox environment were crucial to the Cambrian explosion of life. However, the redox state of the ocean during this transition is unclear. In this study, the carbonate strata of the Dengying Formation in Yunnan Province, South China, were subjected to δ98/95Mo, δ13C, 87Sr/86Sr, and trace element analyses. The low δ98/95Mo results (0‰ ∼ +2‰) of most samples indicate that a shallow-marine sedimentary environment dominated by low-O 2 conditions during the late Ediacaran period (Dengying Formation), but a brief period of marine oxidation existed at this time, reflected by elevated δ98/95Mo values (+2.07‰ ∼ +2.43‰). At this time, δ13C values were increasing, which possibly indicate an increase in primary productivity and photosynthesis in shallow waters, causing oxidation of the shallow seawater. However, two anomalously high δ98/95Mo values (>2.65‰) could have resulted from additional isotope fractionation due to the upwelling of euxinic bottom waters abruptly. In addition, an increase in 87Sr/86Sr ratios lagged the δ13C and δ98/95Mo changes, suggesting that atmospheric changes appear to have lagged oceanic oxidation, but more evidence are needed to prove the relationship. The dynamic changes in the redox conditions of the shallow sea during deposition of the Dengying Formation provided favorable conditions for changes in the atmosphere and the Ediacaran biota. [Display omitted] • The redox conditions of the ocean during the late Ediacaran were studied. • A positive shift of δ98/95Mo that indicates local oceanic oxygenation event is observed. • Enhanced primary productivity is critical to the oceanic oxygenation event. • A time difference between atmospheric and oceanic oxygenation is recognized. [ABSTRACT FROM AUTHOR]

Recently reported specimens of the enigmatic Ediacaran fossil Dickinsonia from Russia show damage and repair that provides evidence of how they grew, and of their biological affinities. Marginal and terminal areas of wilting deformation are necrotic zones separating regenerated growth, sometimes on two divergent axes, rather than a single axis. Necrotic zones of damage to Dickinsonia are not a thick scar or callus, like a wound or amputation. Nor are they smooth transitions to a regenerated tail or arm. The wilted necrotic zone is most like damage by freezing, salt, or sunburn of leaves and lichens, compatible with evidence of terrestrial habitat from associated frigid and gypsic paleosols. Dickinsonia did not regrow by postembryonic addition of modules from a subterminal or patterned growth zone as in earthworms, myriapods, trilobites, crustaceans, and lizards. Rather Dickinsonia postembryonic regrowth from sublethal damage was from microscopic apical and lateral meristems, as in plants and lichens. Considered as fungal, Dickinsonia, and perhaps others of Class Vendobionta, were more likely Glomeromycota or Mucoromycotina, rather than Ascomycota or Basidiomycota. [ABSTRACT FROM AUTHOR]

Fossil feathers have greatly improved our understanding of the evolutionary transition from non-avian dinosaurs to birds and the evolution of feathers, and may be the only evidence for their source animals in the fossil record. Hot spring environments have been demonstrated to be conducive to the preservation of fossils, but internal silicification of feathers was not observed in the only avian carcass so far discovered in ancient hot spring deposits. To determine whether feathers can be internally silicified, here we analyse feathers sampled from a modern hot spring vent pool – Champagne Pool – in New Zealand. Our results of scanning electron microscopy (SEM)-energy dispersive X-ray spectrometry elemental mapping show that the sampled feathers are silicified to different degrees, and one of them is pervasively silicified. SEM observations show that feathers can be silicified at the cellular level. Degradation is involved in the silicification of feathers, as indicated by the reduction of the abundance of carbon and the loss of keratin fibrils. Our findings suggest that ancient deposits of hot spring vent pools are promising targets in search for fossil feathers. [ABSTRACT FROM AUTHOR]

Earth's earliest fossils of complex macroscopic life are recorded in Ediacaran-aged siliciclastic deposits as exceptionally well-preserved three-dimensional casts and molds, known as "Ediacara-style" preservation. Ediacara-style fossil assemblages commonly include both macrofossils of the enigmatic Ediacara Biota and associated textural impressions attributed to microbial matgrounds that were integral to the ecology of Ediacara communities. Here, we use an experimental approach to interrogate to what extent the presence of mat-forming microorganisms was likewise critical to the Ediacara-style fossilization of these soft-bodied organisms. We find evidence that biofilms can play an instrumental role in fostering fossilization. Rapid silica precipitation associated with macroorganism tissues is enhanced in the presence of mat- and biofilm-forming microorganisms. These results indicate that the occurrence of microbial mats and biofilms may have strongly shaped the preservational window for Ediacara-style fossils associated with early diagenetic silica cements, and therefore influenced the distribution and palaeoecological interpretation of the Ediacara Biota fossil record. [ABSTRACT FROM AUTHOR]

Biomineralization is a generic term used to indicate biological‐mediated mineral formation. In carbonate mineralization, nucleation of crystals can be: (1) controlled directly by the organisms, like in the skeletal formation of most metazoans; (2) induced by microbial communities, by indirect precipitation mediated by their metabolic activities; or (3) influenced by organic matter decay, with mineral precipitation on specific non‐living organic cell surfaces. Recognition of these products is a direct marker of biological activity in time and space and is a key element in the study of the biological evolution and of its interactions with the geological processes. In this paper, primary carbonate cements from the Anisian microbial build‐up of the ‘Monte Facito’ Formation (Basilicata region, Southern Italy) have been studied from a geobiological point of view. Optical microscopy, UV‐epifluorescence and micro‐Raman spectroscopy have been applied to investigate the organic mediation on their precipitation. The cements formed in microcavities or on grain substrates, and often show a microstromatolite‐like pattern of growth. They are composed of alternations of cloudy organic and whitish inorganic bands that point to a double phase of mineralization. In the first phase, a biologically induced/influenced biomineralization is confirmed by the presence of organic matter strictly connected with the cloudy bands. This phase is followed by a pure abiotic mineralization that leads to the formation of whitish bands. This process repeated cyclically, ending at the complete filling of the microcavities or because of changes in the chemical conditions of the microsystem, for example, due to burial processes. This model of mineralization is similar to that proposed for primary cements forming in recent beach rocks. The Monte Facito Formation cements could be considered as the product of unconventional biomineralization, and the understanding of their growth process could provide an innovative tool in the research of biological signatures in the fossil record. The term unconventional is here utilized to discriminate this type of biomineralizations from those related to well‐known biotic mineralization processes, like those involved in skeletons and microbialites growth, which can be considered as conventional biomineralizations. [ABSTRACT FROM AUTHOR]

Modular coral-like fossils occur in thrombolitic reefal beds at two stratigraphic levels within the Lower Ordovician (Floian) Barbace Cove Member of the Boat Harbour Formation, in the St. George Group of western Newfoundland. They are here assigned to Reptamsassia n. gen.; R. divergens n. gen. n. sp. is present at both levels, whereas a comparatively small-module species, R. minuta n. gen. n. sp., is confined to the upper level. Reptamsassia n. gen. resembles the Ordovician genus Amsassia in its phacelocerioid structure, back-to-back walls of adjoining modules, module increase by longitudinal fission involving infoldings of the wall, tabula-like structures that are continuous with the vertical module wall, and calices with concave-up bottoms. The new genus is differentiated by its encrusting habit, modules with highly variable growth directions and shapes throughout skeletal growth, and modules that may separate slightly or diverge from one another following fission. Together, Amsassia and Reptamsassia n. gen. are considered to represent a distinct group of calcareous algae, the Amsassiaceae n. fam., which possibly belongs to the green algae. The Early Ordovician origination of Amsassia followed by Reptamsassia n. gen. contributed to the beginning of the rise in diversity on a global scale and in reefal settings during the Great Ordovician Biodiversification Event. Reptamsassia minuta n. gen. n. sp. was an obligate symbiont that colonized living areas on its host, R. divergens n. gen. n. sp., with isolated modules of R. divergens n. gen. n. sp. able to persist in the resulting intergrowth with R. minuta n. gen. n. sp. This is the earliest known symbiotic intergrowth of macroscopic modular species, exemplifying the development of ecologic specialization and ecosystem complexity in Early Ordovician reefs. [ABSTRACT FROM AUTHOR]

Although rare, sedimentary deposits containing exceptionally preserved fossils (i.e., Lagerstätten) have shaped our view on the history of life at particular intervals, such as those recording the Cambrian radiation of animals. Therefore, understanding the processes that lead to the fossilization of unmineralized tissues is crucial to better interpret these fossil assemblages. A key issue on the fossilization of exceptionally preserved fossils is linked to the role of clay minerals in the high-fidelity preservation of recalcitrant and soft tissues. Here, we show for the first time, an association of unusual fibrous clays with carbonaceous fossils (Vendotaenia) in the late Ediacaran Tamengo Formation (Mato Grosso do Sul State, western Brazil). The vendotaeniaceans occur in laminated mudstones/siltstones interpreted as being deposited in outer to distal mid-ramp depositionary settings. The fossils are characterized by ribbon-shaped compressions 0.56 mm in mean width. The fibrous clays are obliquely oriented with respect to the bedding plane, and follow the orientation of tectonically deformed structures. Our mineralogical, geochemical, and petrographic data demonstrate that these clays are mainly composed of chlorite-smectite mixed layered minerals, with >50% chlorite. Altogether, our results suggest that these fibrous minerals formed in the late-diagenetic zone to lower anchizone, reinforcing the previous idea that clay minerals associated with fossils are not necessarily related to the preservation of soft tissues. Instead, the initial preservative pathway in our fossils was probably restricted to organic matter conservation in reducing fine-grained sediments, similar to other deposits with carbonaceous fossils. This newly established mechanism, which involves the formation of clays on organic templates in the late-diagenetic zone, is likely a more widespread phenomenon than previously thought. [ABSTRACT FROM AUTHOR]

Barklice are insects belonging to the order Psocodea. They are herbivorous or detritivorous, and inhabit a wide range of environments. Their oldest fossil record dates back to the late Carboniferous, but it was not until the Cretaceous that they became much more diverse. However, their fossil record could be affected by taphonomic processes due to their tiny size and soft bodies. Here, we present new psocid specimens from five amber‐bearing outcrops in Spain that are Albian in age. One of the specimens, a well‐preserved psocid nymph assigned to †Archaeatropidae, lacks evidence of debris‐carrying behaviour. Some of the specimens belong to the previously known species Archaeatropos alavensis Baz & Ortuño and Preempheria antiqua Baz & Ortuño (Trogiomorpha: Atropetae), providing new anatomical and biogeographical information. Furthermore, we describe a new species, Libanoglaris hespericus sp. nov. (†Archaeatropidae). The diagnosis for the family †Archaeatropidae is emended. The abundance of psocids in Cretaceous amber and their virtual absence in compression outcrops could be due to taphonomic bias. Considerations on the phylogenetic placement of trogiomorphan families and the relationships between †Archaeatropidae and †Empheriidae are included. Today, the least diverse psocid suborder is Trogiomorpha, but this suborder comprises the majority of the Cretaceous psocodean species described to date, possibly due to palaeobiological or evolutionary constraints. Trogiomorphans could have been relegated to marginal habitats by niche competition with psocomorphans. Debris‐carrying behaviour in response to predatory pressure might not have been widely distributed, geographically or phylogenetically, in the Cretaceous psocid nymphs. [ABSTRACT FROM AUTHOR]

The article presents a study which explores the skeletal marine invertebrate phyla appeared during the Cambrian explosion, except for Bryozoa with mineralized skeletons, which first appear in the Early Ordovician. It mentions that skeletal diversity of Early Ordovician bryozoans suggests a preceding interval of diversification.

The rise of eukaryotic macroalgae in the late Mesoproterozoic to early Neoproterozoic was a critical development in Earth's history that triggered dramatic changes in biogeochemical cycles and benthic habitats, ultimately resulting in ecosystems habitable to animals. However, evidence of the diversification and expansion of macroalgae is limited by a biased fossil record. Non-mineralizing organisms are rarely preserved, occurring only in exceptional environments that favor fossilization. Investigating the taphonomy of well-preserved macroalgae will aid in identifying these target environments, allowing ecological trends to be disentangled from taphonomic overprints. Here we describe the taphonomy of macroalgal fossils from the Tonian Dolores Creek Formation (ca. 950 Ma) of northwestern Canada (Yukon Territory) that preserves cm-scale macroalgae. Analytical microscopy, including scanning electron microscopy and tomographic x-ray microscopy, was used to investigate fossil preservation, which was the result of a combination of pyritization and aluminosilicification, similar to accessory mineralization observed in Paleozoic Burgess Shale-type fossils. These new Neoproterozoic fossils help to bridge a gap in the fossil record of early algae, offer a link between the fossil and molecular record, and provide new insights into evolution during the Tonian Period, when many eukaryotic lineages are predicted to have diversified. [ABSTRACT FROM AUTHOR]

The larger-bodied fish fauna of the Kishenehn Formation's Coal Creek Member (Eocene, 43.5 Ma), northwestern Montana, is understudied because of a sampling bias towards small specimens. Small specimens (<10 cm length) of taxa are usually found as mostly to fully complete compression fossils. Relatively larger-bodied fishes, such as amiids (the bowfin Amia calva and close relatives), are only known from fragmentary remains for which taxonomic resolution is only possible to the family level. Here we describe the most complete amiid fossil (USNM 618000) from the Kishenehn Formation. We assign this specimen to the genus Amia based on the presence of pointed coronoid teeth and a long preural region (81 preural centra). The specimen exhibits a combination of features from multiple species, including a total of 89 centra (like Amia calva and Amia scutata), eight ural centra (like Amia scutata and Amia pattersoni), and a concave anteroventral margin on the first postinfraorbital (like Amia hesperia). The lack of more complete specimens of amiids and other larger-bodied taxa is most often attributed to a preservation bias; however, this could also reflect a rarity of amiids in the ecosystem overall or a partitioning of habitat preference away from the shallow, near-shore regions of the ancient lake. This new specimen enhances the known biodiversity of relatively larger-bodied fishes from this region during the Eocene epoch. [ABSTRACT FROM AUTHOR]

The Kuanchuanpu biota (ca. 535 Ma) from the basal Cambrian in South China yields various phosphatized, three-dimensionally preserved microscopic fossils, such as animal embryos, cyanobacteria, and algae. This provides an exceptional window for investigating the rapid divergent evolution of animal phyla in the early Cambrian ocean. However, the fossil eukaryotic algae are poorly documented and are not properly incorporated into the conceptual food web of the Cambrian ocean ecosystem. In this study, we report a new taxon of calathiform alga, Calathophycus irregulatus Tang gen. et sp. nov., and an indeterminate alga, from the Kuanchuanpu biota. Calathophycus irregulatus can be distinguished from other reported phosphatized multicellular algal fossils from the Kuanchuanpu biota and the Ediacaran Weng'an biota (Guizhou Province, China), based on the external morphology and features of cell clump aggregation. The observation of C. irregulatus and the indeterminate alga indicates a certain diversity of algae at the beginning of the Cambrian. Concerning the regularly or irregularly shaped multicellular algal fossils from the Kuanchuanpu Formation, co-occurring spherical fossils, previously interpreted as "cleavage stage" of animal embryos, should be reconsidered in affinity. [ABSTRACT FROM AUTHOR]

The fossil record of macroscelidean mammals is notoriously patchy, with a significant spatial and temporal gap separating faunas from the early Oligocene localities of northern Africa and the early Miocene localities of eastern and southern Africa. Here we describe fossil macroscelideans representing Myohyracinae and Rhynchocyoninae recovered from a rift-fill sequence of richly fossiliferous sandstones in the late Oligocene Nsungwe Formation in the Rukwa Rift Basin of southwestern Tanzania. Radiometrically dated to 25.2 Ma, a new Palaeogene myohyracine taxon (Rukwasengi butleri) is represented by a partial maxilla (RRBP 05409) preserving a lightly worn M2-M3. The M2 exhibits a less hypsodont and mesiodistally elongate morphology than the early Miocene Myohyrax oswaldi, and the three-rooted M3 exhibits a tiny mesially positioned fossette. A new rhynchocyonine (Oligorhynchocyon songwensis) is represented by specimens more brachyodont than the early Miocene Miorhynchocyon. Taken together these finds document a rare window into macroscelidean evolutionary history with diversification of the group near the Palaeogene-Neogene Transition (PNT). Continued exploration offers a refined perspective on mid-Cenozoic faunal and ecosystem dynamics on continental Africa, expanding opportunities for recognising trends in palaeobiological diversity across habitat types and through time. [ABSTRACT FROM AUTHOR]

An incomplete fossil record and unstable phylogenies of extinct taxa hamper reconstructing the early evolution of Caimaninae. We describe previously unpublished articulated fossils of a key species, Tsoabichi greenriverensis from the early Eocene Green River Formation of North America, exhibiting further character evidence for the caimanine affinities of this taxon. Parsimony analysis of modified morphological taxon-character datasets coupled with a critical review of character evolution and published phylogenies reveals that fossil evidence for Palaeogene crown group and Late Cretaceous total-group representatives is unreliable due to uncertain character evolution in early Alligatoridae. The earliest unambiguous fossil age for total and crown-group Caimaninae are 63.5 Ma and 18.06 Ma, respectively. These calibration points follow best practices and are vital for better constrained estimates of time calibrated analyses. Phylogeny continues to imply two separate Caimaninae dispersals between North and South America, but instead of a northward back-dispersal, we find two Palaeogene dispersals to South America an equally likely hypothesis. Miocene taxa of Central America previously assigned to the stem lineage ancestral to South American Caimaninae are reinterpreted as part of a Neogene northward expansion of the crown group. [ABSTRACT FROM AUTHOR]

Ophiolitic rocks of the Lachlan Orogen are important because they can provide key information used to refine existing tectonic models for the orogen. This study focuses on the serpentinite belts within the greater Tumut region of the Lachlan Orogen in southeastern Australia. U–Pb, Lu–Hf, O isotopic and trace-element data collected on zircons from a plagiogranite of the Wambidgee Serpentinite Belt are consistent with their crystallisation from mantle-derived melts. Their juvenile Hf-isotope compositions, with εHf ranging from +7 to +14, and δ18O values ranging from 4.35 to 5.07‰, are close to typical mantle values and clearly within the range defined for zircons from plagiogranites of ophiolitic complexes worldwide. When combined with zircon data available for the Coolac Serpentinite and recent petrogenetic modelling for the Coolac Serpentinite Belt, a new U–Pb age of 486 ± 3 Ma of the Wambidgee zircons constrains the age of formation of oceanic lithosphere in the greater Tumut region to Cambro-Ordovician. An age of 486 ± 3 Ma is reported for zircons from plagiogranite of the Wambidgee Serpentinite Belt in the Tumut region, southern Lachlan Orogen. We tentatively conclude that all serpentinite belts of the Tumut region may be of the same age, at the Cambrian–Ordovician boundary. This Cambro-Ordovician age provides the best estimate for oceanic crust formation in the greater Tumut region. [ABSTRACT FROM AUTHOR]

The article presents a study which explores the paleozoic origins of cheilostome bryozoans and their parental care inferred by a new genome-skimmed phylogeny. It mentions that cheilostome lineage and parental care therein could have Paleozoic origins, much older than the first known fossil record of cheilostomes in the Late Jurassic.

The article provides information about CONASTA 70, the national science teachers conference in Australia. It highlights the conference's theme of innovation and its focus on South Australia's unique aspects, such as Adelaide as a National Park City and the center of Australia's space industry. The article also mentions the program's keynote speakers and the variety of sessions, social activities, and networking events that will be available to attendees.

The origin and early evolution of animal development remain among the many deep, unresolved problems in evolutionary biology. As a compelling case for the existence of pre-Cambrian animals, the Ediacaran embryo-like fossils (EELFs) from the Weng'an Biota (approx. 609 Myr old, Doushantuo Formation, South China) have great potential to cast light on the origin and early evolution of animal development. However, their biological implications can be fully realized only when their phylogenetic positions are correctly established, and unfortunately, this is the key problem under debate. As a significant feature of developmental biology, the cell division pattern (CDP) characterized by the dynamic spatial arrangement of cells and associated developmentalmechanisms is critical to reassess these hypotheses and evaluate the diversity of the EELFs; however, their phylogenetic implications have not been fully realized. Additionally, the scarcity of fossil specimens representing late developmental stages with cell differentiation accounts for much of this debate too. Here, we reconstructed a large number of EELFs using submicron resolution X-ray tomographic microscopyandfocusedontheCDPsandassociated developmentalmechanisms as well as features of cell differentiation. Four types of CDPs and specimens with cell differentiation were identified. Contrary to the prevailing view, our results together with recent studies suggest that the diversity and complexity of developmental mechanisms documented by the EELFs are much higher than is often claimed. The diverse CDPs and associated development features including palintomic cleavage, maternal nutrition, asymmetric cell divisions, symmetry breaking, establishment of polarity or axis, spatial cell migration and differentiation constrain some, if not all, EELFs as total-group metazoans. [ABSTRACT FROM AUTHOR]

The article presents the discussion on impact of Chinese palaeontology on evolutionary research. Topics include Chinese palaeontologists developing expertise in various groups of fossil organisms, along with the well established biostratigraphy providing a solid foundation for further palaeontological research in China; and using submicron resolution X-ray tomographic microscopy focusing on the cell division pattern, associated developmental mechanisms, and features of cell differentiation.

The Early Ordovician is a key interval for our understanding of the evolution of life on Earth as it lays at the transition between the Cambrian Explosion and the Ordovician Radiation and because the fossil record of the late Cambrian is scarce. In this study, assembly processes of Early Ordovician trilobite and echinoderm communities from the Central Anti-Atlas (Morocco), the Montagne Noire (France), and the Cordillera Oriental (Argentina) are explored. The results show that dispersal increased diachronically in trilobite communities during the Early Ordovician. Dispersal did not increase for echinoderms. Dispersal was most probably proximally triggered by the planktic revolution, the fall in seawater temperatures, changes in oceanic circulation, with an overall control by tectonic frameworks and phylogenetic constraints. The diachronous increase in dispersal within trilobite communities in the Early Ordovician highlights the complexity of ecosystem structuring during the early stages of the Ordovician Radiation. As Early Ordovician regional dispersal was followed by well-documented continental dispersal in the Middle/Late Ordovician, it is possible to consider that alongside a global increase in taxonomic richness, the Ordovician Radiation is also characterized by a gradual increase in dispersal. [ABSTRACT FROM AUTHOR]

The Italian Northern Apennines are acknowledged as the place where ichnology was born, but there is comparatively little work about their ichnological record. This study bridges this gap by describing two new ichnosites from the locality of Pierfrancesco, which preserve an abundant, low-disparity trace-fossil assemblage within the Late Cretaceous beds of the M. Cassio Flysch. Results show that lithofacies and ichnotaxa are rhythmically organized. The base of each cycle consists of Megagrapton-bearing calciclastic turbidites, which are overlain by marlstone beds with an abundant, low-disparity assemblage of trace fossils. This includes Chondrites intricatus, C. patulus, C. targionii, C. recurvus and Cladichnus fischeri. The cycle top consists of mudstones with no distinct burrows. The rhythmic pattern of Pierfrancesco reflects a deep-sea ecological succession, in which species and behaviour changed as turbidite-related disturbances altered the seafloor. This study opens the question of whether the Chondrites-Cladichnus ichnocoenosis represents low-oxygen or nutrient-poor settings. [ABSTRACT FROM AUTHOR]

Records of diagenetically mineralized, filamentous, cavity-dwelling microorganisms extend back to strata from the early Paleoproterozoic (2400 Ma). In North Greenland (Laurentia), they are first known from the Ediacaran (Neoproterozoic; ca. 600 Ma) Portfjeld Formation of southern Peary Land, in association with a biota similar to that of the Doushantuo Formation of China. The Portfjeld Formation cavity dwellers are compared with more widespread occurrences in Cambrian (Series 2, Stage 4, Miaolingian Series) strata from the same region in which assemblages in postmortal shelter structures within articulated acrotretoid brachiopods and other invertebrates are common. All specimens were recovered by digestion of carbonate samples in weak acids. The described fossils are preserved as mineral encrusted threads but this diagenetic phosphatization unfortunately obscures their biological identity. [ABSTRACT FROM AUTHOR]

Choanoflagellates are microeukaryotes that inhabit freshwater and marine environments and have long been regarded as the closest living relatives of Metazoa. Knowledge on the evolution of choanoflagellates is key for the understanding of the ancestry of animals, and although molecular clock evidence suggests the appearance of choanoflagellates by late Neoproterozoic, no specimens of choanoflagellates are known to occur in the fossil record. Here the first putative occurrence of choanoflagellates in sediments from the Cretaceous (Cenomanian–Turonian) is described by means of several cutting-edge petrographic techniques, and a discussion of its paleoenvironmental significance is performed. Furthermore, their placement in the organic matter classification systems is argued, with a placement in the Zoomorph Subgroup (Palynomorph Group) of the dispersed organic matter classification system being proposed. Regarding the ICCP System 1994, incorporation of choanoflagellates is, at a first glance, straightforward within the liptinite group, but the definition of a new maceral may be necessary to accommodate the genetic origin of these organisms. While modern choanoflagellates may bring light to the cellular foundations of animal origins, this discovery may provide an older term of comparison to their extant specimens and provide guidelines for possible identification of these organic components in other locations and ages throughout the geological record. [ABSTRACT FROM AUTHOR]

This study reports five ostracod taxa from the Middle Devonian Naidaijin Formation, Kumamoto Prefecture, Kyushu, Japan comprising shelf‐nearshore beyrichiid and bairdiocypridoid species, and two species of Bairdia. This is the first report of ostracod fossils from the Devonian strata in the Kurosegawa belt. Most analyzed fossils are the same species as those found in the Middle Devonian strata of Yunnan and Guangxi provinces in South China, indicating that the Kurosegawa belt of Kyushu shared biogeographical affinities with the palaeo‐equatorial South China paleocontinent. [ABSTRACT FROM AUTHOR]

Bioturbation has long been considered an antagonist of microbialite development and preservation, because metazoan grazing and burrowing destroy benthic microbial communities. However, metazoan bioturbation, in conjunction with microbial accretion, may have had a significant role in the morphogenesis of some columnar microbialites, as suggested by the case study presented and by some Phanerozoic and Upper Proterozoic analogues discussed here. Late Miocene in age, the studied microbial biostrome developed in a western Mediterranean restricted shallow‐water platform dominated by grainy sediments and with a notable influence of bioturbation. This study is focused on the complex accretionary history of the columnar microbialite biostrome and on its striking dark grey colour, which is attributed to Mn‐oxyhydroxides precipitated during meteoric diagenesis linked to subaerial exposure. The characteristic columnar structure of the microbialite biostrome has features consistent with an accretionary origin of the columns, but also has features suggesting metazoan disruption. Therefore, a new morphogenetic model for columnar microbialites is presented, highlighting the concomitant roles of microbial accretion, bioturbation and grainy sediment infill of the intercolumn space. Whether this model is an exception or a rule, should be tested on other examples of Phanerozoic and Upper Proterozoic columnar microbialites. Nevertheless, this model is a step forward in understanding the complex microbe–metazoan interactions as constructive coexistence rather than just as destructive competition. [ABSTRACT FROM AUTHOR]

Digital metrologywas applied to evaluate 3D models of the unique skull of a fossil tetrapod, Madygenerpeton pustulatum, generated using various 3D digitization methods. The skull surface is covered by minute tubercles making it challenging for digitization with appropriate accuracy. Uniqueness and fragility of the specimen preclude the use of tactile measuring systems for creating a standardized reference model. To overcome this problem, comparative analysis of the triangulated models generated from the clouds of points obtained with seven different devices was conducted using the Geomagic Studio and Autodesk PowerShape CAD software. In the proposed approach, geometrically and dimensionally closest-fitting models underwent detailed statistical analysis between surface polygons in three steps. First, 3D models obtained from different scanning methods were compared with each other in couples. Next, statistical analysis of the differences between the coupled models was performed. Finally, a rating list of the models related to the required accuracy was prepared. The proposed approach is applicable to any other scanned object, especially in palaeontological applications, where each object is unique and exhibits individual features. [ABSTRACT FROM AUTHOR]

Recent discoveries of trackways and trails on ancient tidal flats at Blackberry Hill, Wisconsin, USA, have transformed our understanding of the initial invasion of land, 500 Ma. Huge slug‐like molluscs grazed on microbial mats. Euthycarcinoid (stem myriapod) death traces (mortichnia) suggest that they did not come onto land to feed or breed, but simply to survive; Moon was closer to Earth then, and massive tides stranded animals in tidal pools that gradually dried up. [ABSTRACT FROM AUTHOR]

The fossil record of Darwin wasps (Ichneumonidae) is extremely understudied relative to their enormous extant diversity, with only around 300 species described. Moreover, the taxonomic placement of many of the fossils is based on an outdated classification system. We here revise 18 ichneumonid fossils, all described before the most comprehensive revision of ichneumonid classification by Henry Townes. After a careful reinterpretation of character evidence, we leave the original placement of only five fossils, while expressing uncertainty about the placement of two of them, Pimpla? seyrigi Theobald and Polysphincta? inundata Brues, by following the principles of open nomenclature. In addition, we move Parapimpla rhenana Theobald, 1937 stat. rev. from Pimplinae to Ctenopelmatinae. We describe a new phygadeuontine genus to accommodate two fossils previously described in Pimplinae, Armadilleon morticinus (Brues) gen. et comb. nov. and A. petrorum (Brues) gen. et comb. nov. Finally, we change the genus and, almost always, the subfamily placement for ten fossils: Hallocinetus? arvernus (Piton) comb. nov., Dimophora? longicornis (Theobald) comb. nov., Dimophora? wickhami (Cockerell) comb. nov., Lycorina? indura (Theobald) comb. nov., Acerataspis? revelata (Brues) comb. nov., Hypsicera? solidata (Brues) comb. nov., Orthocentrus? mortuaria (Brues) comb. nov., Zagryphus tilloyi (Theobald) comb. nov., Lithoserix antiquus (Saussure) comb. nov. and Monoblastus? senilis (Brues) comb. nov. Our revision highlights the need for the re-interpretation of perhaps a majority of ichneumonid fossils and for widely adopting the open nomenclature framework. This framework allows uncertainty in fossil classification to be expressed in an intuitive and explicit manner, which contributes to alleviating misinterpretation of the palaeontological literature, for instance in phylogenetic dating studies. [ABSTRACT FROM AUTHOR]

Many Ediacaran macrofossils are apparently composed of unique pneus (similar, repetitive tubular modules) forming a variety of body shapes by combinations of modular growth regimes. The large‐scale disappearance of Ediacaran macro‐organisms at the end of the Precambrian leaves this now extinct modular body plan only rarely reported from the Cambrian onwards. Mackenzia costalis is an enigmatic and poorly understood soft‐bodied organism from the middle Cambrian, and is a possible surviving member of the Ediacaran macrobiota. Here, we describe a new mackenziid, Paramackenzia canalifera, from the early Cambrian Chengjiang biota, Yunnan Province, south‐west China. It has a body plan comprising longitudinal tubular modules that are radially arranged to form a cylindrical body with a basal attachment. Each tubular module is enclosed by an inner and outer concentric membrane, separated from adjacent modules by a thin lamellar sheet. Infilling sediment and preservation of dark, basal stains at the inner and outer membranes reveal a pore–canal system within the lamellae, connecting the internal cavity to the exterior. This arrangement of tubular modules is similar to that of several macroscopic Ediacaran species, including erniettomorphs and dickinsoniomorphs, which were constructed of serial hydrostatic modules referred to as 'pneus'. The mackenziid pore system is similar to that of sponges and archaeocyathids in function and feeding strategy, but the overall anatomy precludes affiliation to this phylum. We suggest that mackenziids are most likely to be a blastic or diploblastic anatomical grade of stem eumetazoans, similar to other modular Ediacaran macro‐organisms. [ABSTRACT FROM AUTHOR]

Preserved lipid biomarkers provide a unique window onto the biology of fossil organisms. A new study uses lipids to assess the gut contents of three fossils from the 'dawn of animals' in the Ediacaran, with implications for their feeding behaviors. [ABSTRACT FROM AUTHOR]

Fossil remains, including a vertebral centrum and some scales, from the Lower Cretaceous Marizal Formation of the Tucano Basin are described as belonging to an amiid fish likely of the subfamily Vidalamiinae. A comparison made from the largest midline predorsal scale with scales in several species of amiids suggests a standard length of approximately 140 cm for the Marizal Formation's species. This amiid represents the largest fossil fish known from the Marizal ichthyofauna in the palaeobiota and likely was an apex predator. [ABSTRACT FROM AUTHOR]

A total of 30 specimens of “Pholas tzayi Hu, 1992” were collected from the Chinshui Shale (Upper Pliocene) at the Laotinliao Creek, Touwu Township, Miaoli County, Taiwan. Among them, 18 specimens are preserved with both valves and 8 specimens are preserved with diagnostic characters. Field observation shows that many specimens are preserved with unbroken valves and buried with the posterior end pointing upward and perpendicular to the bedding; thus, stratigraphic facing can be inferred based on pholadid bivalves buried in situ. This is important because Chinshui Shale consists of intensely bioturbated, muddy sandstone and organic-rich mudstone without obvious bedding surfaces. The layer of intact pholadid bivalves not only provides clues about original seafloor conditions but also contains information about original bedding orientation. Furthermore, this layer has been noted in more than one locality and can be used as a key layer for correlation. Rapid sedimentation events, such as obrution, can contribute to the death of organisms. Organisms found in obrution deposits tend to have a better chance to get preserved in the fossil records because that rapid burial implies anoxic or dysoxic conditions within the sediment layers preventing further bioerosion due to scavenging activities. This study helps us to understand the invertebrate faunal evolution near the Plio-Pleistocene boundary in Taiwan. Due to the short range of occurrence of this endemic species “P. tzayi” and has been reported from several localities, it is recognized as one of the key fossils for Chinshui Shale. [ABSTRACT FROM AUTHOR]

We discuss a recent assessment by Dörken et al. (2021) regarding the affinities of the Eocene fossil species Huncocladus laubenfelsii from Laguna del Hunco (Patagonia, Argentina). We originally (Andruchow-Colombo et al. , 2019) assigned this species to the conifer family Podocarpaceae as the first certain South American macrofossil record of the phyllocladoid lineage (Huncocladus + Phyllocladus), based on a combination of numerous macro- and micromorphological vegetative characters. However, Dörken et al. (2021) rejected the podocarpaceous affinity of H. laubenfelsii and considered it to be more closely related to the cycad genera Bowenia or Eobowenia. Their assessment was based almost entirely on two cuticular characters, with only superficial consideration of the abundant additional evidence available that included several diagnostic macromorphological features. We review the two characters mentioned by these authors, and other features, and find that their suggestion is contradicted by the available evidence, maintaining our original assignment. Critical characters include presence/absence of a midvein, secondary venation pattern, arrangement and general morphology of the photosynthetic structures, and morphology and disposition of epidermal cells. [ABSTRACT FROM AUTHOR]

Thrombolites and ichnofossils are well‐preserved in a carbonate succession of the Cambrian (Miaolingian Series) Zhangxia Formation, south North China Block. This provides a chance to investigate the factors controlling the distributions of thrombolites and metazoans. Three types of thrombolites are identified, on the basis of clot shape and their array styles, namely, bushy, columnar, and blocky thrombolites. Bushy thrombolites occur in the lower part of the study unit, columnar thrombolites in the middle, and blocky thrombolites in the upper. Thrombolitic intervals alternate with bioturbated limestones, with the latter including two ichnogenera: Balanoglossites triadicus Mägdefrau, 1932 and Sulcolithos variabilis Knaust, 2019. Both thrombolites and bioturbated limestones are covered by oolitic limestones. The facies analysis indicates depositional environments from deep to shallow subtidal, then to oolitic shoals upwards. Such a sequence represents an overall shallowing‐upward trend. Thrombolites generally flourished during transgressions, whereas bioturbated and oolitic limestones represent regressive systems. Thus, relative sea level was a main factor controlling the alternations of thrombolites and ichnofossils in the Zhangxia Formation. Although there is no clear evidence that bioturbation can directly destroy thrombolites, exploration of new habitats by benthic animals and the increasing mixing degree of substrates could have destroyed the previous firmground substrate required for thrombolite development. The alternations of thrombolites and bioturbated limestones demonstrate that ecological conditions frequently fluctuated in the neritic environment during the Middle Cambrian. [ABSTRACT FROM AUTHOR]

Cantharidae is a diverse group of soft-bodied beetles and frequently occurs in the Mid-Cretaceous (c. 99 Mya) amber of Myanmar. In the present paper, three new soldier beetles, Cretocantharis veda gen. & sp. nov. , Palaeocantharis panna gen. & sp. nov. and Hukawngichthyurus maha sp. nov. are reported. A phylogenetic reconstruction of Cantharidae, including all extant subfamilies and tribes, corroborates a distinct lineage comprising cantharine-like cantharids from Burmese amber as sister to Silini (Silinae), revealing that the current subfamilial placement is probably inadequate. Together with our results and recent molecular phylogenetic frameworks, it reveals that subfamilies of Cantharidae evolved during the Cretaceous period and highlights a probable Gondwanan ancestry of main cantharid groups. Our topology also proposes that the systematically controversial tribe Tytthonyxini of Silinae constitutes an independent clade sister to Malthininae, rather than the component of Silinae. Furthermore, Archaeomalthodes rosetta , previously placed in Malthininae, is recovered as a member of Dysmorphocerinae, representing the oldest fossil record for this subfamily and enhancing the Gondwanan origin hypothesis of Burmese amber biota. The previous interpretation of reticulated elytra as a lycid-mimicry for the Cretaceous cantharid fossils and pleisiomorphy of Cantharidae are challenged and discussed. [ABSTRACT FROM AUTHOR]

We here report a new elateroid, Anoeuma lawrencei Li, Kundrata and Cai gen. et sp. nov., from mid-Cretaceous Burmese amber. Though superficially similar to some soft-bodied archostematans, Anoeuma could be firmly placed in the polyphagan superfamily Elateroidea based on the hind wing venation. Detailed morphological comparisons between extant elateroids and the Cretaceous fossils suggest that the unique character combination does not fit with confidence into any existing soft-bodied elateroid group, although some characters indicate possible relationships between Anoeuma and Omalisinae. Our discovery of this new lineage further demonstrates the past diversity and morphological disparity of soft-bodied elateroids. [ABSTRACT FROM AUTHOR]

The article presents the tempo of Ediacaran evolution. Topic include the rise of complex macroscopic life occurred during the Ediacaran Period, an interval that witnessed large-scale disturbances to biogeochemical systems, and the Ediacaran chronostratigraphic framework is of insufficient resolution to provide robust global correlation schemes or test hypotheses for the role of biogeochemical cycling in the evolution of complex life.

Here we report a parosteal osteosarcoma, a malignant bone neoplasm, in a right femur assigned to the Quaternary ground sloth Nothrotherium maquinense. The specimen was collected at Lapa dos Peixes I, a cave located at Serra do Ramalho plateau, Bahia, Brazil. The diagnosis was based on the macroscopic, radiologic and histologic appearance of the lesion. The presence of this pathology may indicate that the individual suffered from local pain, localised swelling and limitation of joint movement, which would have been extremely harmful for its life. Even though neoplasms are recognised in almost all metazoans, this is the first case of cancer reported for a Quaternary non-human mammal and appears to be the first report of this specific form of bone cancer in the fossil record. [ABSTRACT FROM AUTHOR]

Fossil material of Ediacaran macroscopic algae has been found in the Vendian reference section, in the upper part of the Dal'nyaya Taiga Group of the Ura uplift, in the southern part of the Siberian Platform. The macrofossils discovered in the upper part of the Dal'nyaya Taiga Group are morphologically similar to carbonaceous Miaohen biota from the Ediacaran of South China; however, they occupy a lower stratigraphic level. Hence, the finding of algae macrofossils both develops our understanding of the evolution of marine ecosystems in the Proterozoic and demonstrates that the paleontological potential of one of the most representative Upper Precambrian sections has not been fully plumbed. [ABSTRACT FROM AUTHOR]

The fossil record of non‐biomineralized animals and tissues provides important insight into deep‐time evolutionary events. Interpretation of these highly variable remains requires an understanding of how both decay and preservation lead to fossilization. Here we establish a quantitative approach that unites data from decay experiments of extant taxa with preservation mode of fossils, allowing evaluation of both information loss and information retention, and their interaction, in non‐biomineralized fossils. We illustrate our approach using fossil data from two Lagerstätten with distinct taphonomic regimes, one characterized by phosphatization, and the other by pyritization of non‐biomineralized tissues. This demonstrates that frequency of occurrence of characters in fossil taxa is significantly correlated with sequences of character decay observed in extant comparator organisms, and that decay prone and decay resistant characters have distinct preservation modes; the former are mineralized and the latter are organically preserved. The methods and principles applied here to non‐biomineralized vertebrates are applicable to other exceptionally‐preserved fossils and allow for identification of systematic biases in fossil specimen completeness, character retention and the mode of their preservation. Furthermore, our analyses validates experimental decay in supporting the interpretation of anatomy in non‐biomineralized fossils. [ABSTRACT FROM AUTHOR]

Small shelly fossils (SSFs) are highly informative of the 'Cambrian explosion'. Their palaeobiodiversity has been documented from lower Cambrian deposits worldwide but it remains elusive in areas such as Iran, despite this region occupying a critical position on the north‐western Gondwana margin during the early Cambrian. This new study of the SSFs of the lower Cambrian of northern Iran provides a large new dataset from this understudied area. We revise the micropalaeontological signal of the Soltanieh Formation of the Alborz Mountains and introduce novel data from the Soltanieh and overlying Barut Formations of the Soltanieh Mountains. The new, solid taxonomic and stratigraphic SSF data enable us to distinguish two successive microfaunal assemblages. The first occurs in the Soltanieh Formation of the Soltanieh and Alborz Mountains and is dominated by anabaritids (Anabarites trisulcatus, A. ex gr. trisulcatus, A. tristichus, A. dalirense sp. nov., Cambrotubulus decurvatus) along with protoconodonts (Protohertzina anabarica and P. unguliformis), maikhanellids (Maikhanella multa, Purella squamulosa and Purella sp.), Aetholicopalla adnata, indeterminate cones and irregular tubes. The second assemblage, from the Barut Formation, is dominated by a diverse assemblage of molluscs (Oelandiella korobkovi and cap‐shaped morphotypes). Siphogonuchitid sclerites also occur in both assemblages. The two SSF assemblages are characteristic of the Terreneuvian. Our dataset enables us to assess the sequence of faunal change of the Ediacaran–Cambrian transition; in contrast to the tube–sclerite–brachiopod succession presented in the literature, the Iranian fauna changes from one dominated by tubes and sclerites, to one dominated by molluscs and sclerites. [ABSTRACT FROM AUTHOR]

Tardigrades are a diverse group of charismatic microscopic invertebrates that are best known for their ability to survive extreme conditions. Despite their long evolutionary history and global distribution in both aquatic and terrestrial environments, the tardigrade fossil record is exceedingly sparse. Molecular clocks estimate that tardigrades diverged from other panarthropod lineages before the Cambrian, but only two definitive crown-group representatives have been described to date, both from Cretaceous fossil deposits in North America. Here, we report a third fossil tardigrade from Miocene age Dominican amber. Paradoryphoribius chronocaribbeus gen. et sp. nov. is the first unambiguous fossil representative of the diverse superfamily Isohypsibioidea, as well as the first tardigrade fossil described from the Cenozoic. We propose that the patchy tardigrade fossil record can be explained by the preferential preservation of these microinvertebrates as amber inclusions, coupled with the scarcity of fossiliferous amber deposits before the Cretaceous. [ABSTRACT FROM AUTHOR]

Permian–Triassic boundary microbialites (PTBMs) that formed directly after the end-Permian extinction in the South China Block are dominated by one structure, a lobate-form calcium carbonate construction that created extensive very thin (ca. 2–20 m thick) framework biostromes in shallow marine environments, effectively occupying the ecological position of the prior pre-extinction Permian reefs and/or associated carbonates. In the field, vertical sections show the microbialite is dendrolite (branched) and thrombolite (clotted), but because thrombolite may include branched portions, its structure is overall best classed as thrombolite. In the field and in polished blocks, the microbial material appears as dark carbonate embedded in lighter-coloured micritic sediment, where details cannot be seen at that scale. In thin section, in contrast to the largely unaltered micritic matrix, the microbial constructor is preferentially partly to completely recrystallised, but commonly passes gradationally over distances of a few mm to better-preserved areas comprising 0.1–0.2 mm diameter uneven blobs of fine-grained calcium carbonate (micrite to microsparite). The lobate architecture comprises branches, layers and clusters of blobs ca. 1–20 mm in size, and includes constructed cavities with geopetal sediments, cements and some deposited small shelly fossils. Individual blobs in the matrix may be fortuitous tangential cross sections through margins of accumulated masses, but if separate, may represent building blocks of the masses. The lobate structure is recognised here as a unique microbial taxon and named Calcilobes wangshenghaii n. gen., n. sp. Calcilobes reflects its calcium carbonate composition and lobate form, wangshenghaii for the Chinese geologist (Shenghai Wang) who first detailed this facies in 1994. The structure is interpreted as organically built, and may have begun as separate blobs on the sea floor sediment (that was also composed of micrite but is interpreted as mostly inorganic), by microbial agglutination of micrite. Because of its interpreted original micritic–microsparitic nature, classification as either a calcimicrobe (calcified microbial fossil) or a sedimentary microbial structure is problematic, so C. wangshenghaii has uncertain affinity and nature. Calcilobes superficially resembles Renalcis and Tarthinia, which both form small clusters in shallow marine limestones and have similar problems of classification. Nevertheless, Calcilobes framework architecture contrasts both the open branched geometry of Renalcis, and the small tighter masses of Tarthinia, yet it is more similar to Tarthinia than to Renalcis, and may be a modification of Tarthinia, noting that Tarthinia is known from only the Cambrian. Calcilobes thus joins Renalcis, Tarthinia and also Epiphyton (dendritic form) and others, as problematic microbial structures. Calcilobes has not been recognised elsewhere in the geological record and may be unique to the post-end-Permian extinction facies. C. wangshenghaii occurs almost exclusively in the South China Block, which lay on the eastern margin of Tethys Ocean during Permian–Triassic boundary times; reasons for its absence in western Tethys, except for comparable fabrics in one site in Iran and another in Turkey, are unknown. [ABSTRACT FROM AUTHOR]

Problematic fossils are described from Late Ediacaran to Early Cambrian red sandstones of the Arumbera Sandstone, Grant Bluff, and Central Mount Stuart Formations in central Australia, within a new systematic classification of Vendobionta. Arumberia banksi has been one of the most problematic of Ediacaran fossils, at first considered a fossil and then a sedimentary or organo-sedimentary structure. Our re-examination of the type material and collection of new material reveals misconceptions about its topology: it was a recessive fossil on the bed top, protruding down from the counterpart overlying slab. The concave-up body was 3 mm thick and chambered above a diffuse lower surface, so not a sedimentary structure. Also re-evaluated is the discoid fossil Hallidaya brueri, here including "Skinnera brooksi' as its upper surface. A new species (Noffkarkys storaaslii gen. et sp. nov.) is a multilobed frond with regular, fine, trapezoidal quilts. Three new records of Trepassia wardae, Dickinsonia costata, and Ernietta plateauensis are reported from the Arumbera and Grant Bluff Formations. Reevaluation of palaeomagnetic and biostratigraphic data suggest an hiatus of 26 million years at the Ediacaran–Cambrian boundary within the Arumbera Formation, but some of this missing time is filled by the Grant Bluff and Central Mount Stuart Formations. [ABSTRACT FROM AUTHOR]

A new species, Syzygium guipingensis sp. nov. (Myrtaceae), is described based on mummified fossil wood from the Miocene Erzitang Formation of Guiping Basin, Guangxi, South China. This species represents the most ancient reliable fossil record of the genus Syzygium in eastern Asia, showing the greatest similarity to the extant species S. buxifolium Hook. et Arnott. Its occurrence in the Miocene is consistent with the diversification age of the Asian lineage within Syzygium as estimated by molecular dating (11.4 Ma). The fossil record of Syzygium suggests that this genus migrated from Australia to eastern Asia in the Miocene, coincidently with the formation of island chains between these continents. [ABSTRACT FROM AUTHOR]