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Sponges are the most basal metazoan phylum 1 and may have played important roles in modulating the redox architecture of Neoproterozoic oceans 2 . Although molecular clocks predict that sponges diverged in the Neoproterozoic era 3,4 , their fossils have not been unequivocally demonstrated before the Cambrian period 5-8 , possibly because Precambrian sponges were aspiculate and non-biomineralized 9 . Here we describe a late-Ediacaran fossil, Helicolocellus cantori gen. et sp. nov., from the Dengying Formation (around 551-539 million years ago) of South China. This fossil is reconstructed as a large, stemmed benthic organism with a goblet-shaped body more than 0.4 m in height, with a body wall consisting of at least three orders of nested grids defined by quadrate fields, resembling a Cantor dust fractal pattern. The resulting lattice is interpreted as an organic skeleton comprising orthogonally arranged cruciform elements, architecturally similar to some hexactinellid sponges, although the latter are built with biomineralized spicules. A Bayesian phylogenetic analysis resolves H. cantori as a crown-group sponge related to the Hexactinellida. H. cantori confirms that sponges diverged and existed in the Precambrian as non-biomineralizing animals with an organic skeleton. Considering that siliceous biomineralization may have evolved independently among sponge classes 10-13 , we question the validity of biomineralized spicules as a necessary criterion for the identification of Precambrian sponge fossils., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Macrofossils with unambiguous biogenic origin and predating the one-billion-year-old multicellular fossils Bangiomorpha and Proterocladus interpreted as crown-group eukaryotes are quite rare. Horodyskia is one of these few macrofossils, and it extends from the early Mesoproterozoic Era to the terminal Ediacaran Period. The biological interpretation of this enigmatic fossil, however, has been a matter of controversy since its discovery in 1982, largely because there was no evidence for the preservation of organic walls. Here we report new carbonaceous compressions of Horodyskia from the Tonian successions (~950-720 Ma) in North China. The macrofossils herein with bona fide organic walls reinforce the biogenicity of Horodyskia. Aided by the new material, we reconstruct Horodyskia as a colonial organism composed of a chain of organic-walled vesicles that likely represent multinucleated (coenocytic) cells of early eukaryotes. Two species of Horodyskia are differentiated on the basis of vesicle sizes, and their co-existence in the Tonian assemblage provides a link between the Mesoproterozoic (H. moniliformis) and the Ediacaran (H. minor) species. Our study thus provides evidence that eukaryotes have acquired macroscopic size through the combination of coenocytism and colonial multicellularity at least ~1.48 Ga, and highlights an exceptionally long range and morphological stasis of this Proterozoic macrofossils., (© 2023. The Author(s).)

The colonization of land by fungi had a significant impact on the terrestrial ecosystem and biogeochemical cycles on Earth surface systems. Although fungi may have diverged ~1500-900 million years ago (Ma) or even as early as 2400 Ma, it is uncertain when fungi first colonized the land. Here we report pyritized fungus-like microfossils preserved in the basal Ediacaran Doushantuo Formation (~635 Ma) in South China. These micro-organisms colonized and were preserved in cryptic karstic cavities formed via meteoric water dissolution related to deglacial isostatic rebound after the terminal Cryogenian snowball Earth event. They are interpreted as eukaryotes and probable fungi, thus providing direct fossil evidence for the colonization of land by fungi and offering a key constraint on fungal terrestrialization.

The origin of motility in bilaterian animals represents an evolutionary innovation that transformed the Earth system. This innovation probably occurred in the late Ediacaran period-as evidenced by an abundance of trace fossils (ichnofossils) dating to this time, which include trails, trackways and burrows 1-3 . However, with few exceptions 4-8 , the producers of most of the late Ediacaran ichnofossils are unknown, which has resulted in a disconnection between the body- and trace-fossil records. Here we describe the fossil of a bilaterian of the terminal Ediacaran period (dating to 551-539 million years ago), which we name Yilingia spiciformis (gen. et sp. nov). This body fossil is preserved along with the trail that the animal produced during a death march. Yilingia is an elongate and segmented bilaterian with repetitive and trilobate body units, each of which consists of a central lobe and two posteriorly pointing lateral lobes, indicating body and segment polarity. Yilingia is possibly related to panarthropods or annelids, and sheds light on the origin of segmentation in bilaterians. As one of the few Ediacaran animals demonstrated to have produced long and continuous trails, Yilingia provides insights into the identity of the animals that were responsible for Ediacaran trace fossils.

Ediacaran trace fossils provide key paleontological evidence for the evolution of early animals and their behaviors. Thus far, however, this fossil record has been limited to simple surface trails and relatively shallow burrows. We report possible trackways, preserved in association with burrows, from the terminal Ediacaran Shibantan Member (ca. 551 to ca. 541 million years ago) in the Yangtze Gorges area of South China. These trace fossils represent the earliest known trackways. They consist of two rows of imprints arranged in poorly organized series or repeated groups. These trackways may have been produced by bilaterian animals with paired appendages, although the phylum-level phylogenetic affinity of the trace makers remains unknown. It is possible that the trackways and associated burrows were produced by the same trace maker, indicating a complex behavior involving both walking and burrowing. Together, these trackways and burrows mark the arrival of a new era characterized by an increasing geobiological footprint of bilaterian animals.

Molar tooth structures are ptygmatically folded and microspar-filled structures common in early- and mid-Proterozoic (∼2,500-750 million years ago, Ma) subtidal successions, but extremely rare in rocks <750 Ma. Here, on the basis of Mg and S isotopes, we show that molar tooth structures may have formed within sediments where microbial sulphate reduction and methanogenesis converged. The convergence was driven by the abundant production of methyl sulphides (dimethyl sulphide and methanethiol) in euxinic or H2S-rich seawaters that were widespread in Proterozoic continental margins. In this convergence zone, methyl sulphides served as a non-competitive substrate supporting methane generation and methanethiol inhibited anaerobic oxidation of methane, resulting in the buildup of CH4, formation of degassing cracks in sediments and an increase in the benthic methane flux from sediments. Precipitation of crack-filling microspar was driven by methanogenesis-related alkalinity accumulation. Deep ocean ventilation and oxygenation around 750 Ma brought molar tooth structures to an end.

Phosphorites of the Ediacaran Doushantuo Formation (∼600 million years old) yield spheroidal microfossils with a palintomic cell cleavage pattern. These fossils have been variously interpreted as sulphur-oxidizing bacteria, unicellular protists, mesomycetozoean-like holozoans, green algae akin to Volvox, and blastula embryos of early metazoans or bilaterian animals. However, their complete life cycle is unknown and it is uncertain whether they had a cellularly differentiated ontogenetic stage, making it difficult to test their various phylogenetic interpretations. Here we describe new spheroidal fossils from black phosphorites of the Doushantuo Formation that have been overlooked in previous studies. These fossils represent later developmental stages of previously published blastula-like fossils, and they show evidence for cell differentiation, germ-soma separation, and programmed cell death. Their complex multicellularity is inconsistent with a phylogenetic affinity with bacteria, unicellular protists, or mesomycetozoean-like holozoans. Available evidence also indicates that the Doushantuo fossils are unlikely crown-group animals or volvocine green algae. We conclude that an affinity with cellularly differentiated multicellular eukaryotes, including stem-group animals or algae, is likely but more data are needed to constrain further the exact phylogenetic affinity of the Doushantuo fossils.

Ediacara fossils are central to our understanding of animal evolution on the eve of the Cambrian explosion, because some of them likely represent stem-group marine animals. However, some of the iconic Ediacara fossils have also been interpreted as terrestrial lichens or microbial colonies. Our ability to test these hypotheses is limited by a taphonomic bias that most Ediacara fossils are preserved in sandstones and siltstones. Here we report several iconic Ediacara fossils and an annulated tubular fossil (reconstructed as an erect epibenthic organism with uniserial arranged modular units), from marine limestone of the 551-541 Ma Dengying Formation in South China. These fossils significantly expand the ecological ranges of several key Ediacara taxa and support that they are marine organisms rather than terrestrial lichens or microbial colonies. Their close association with abundant bilaterian burrows also indicates that they could tolerate and may have survived moderate levels of bioturbation.

On the basis of putative nuclei and endospores, Huldtgren et al. (Reports, 23 December 2011, p. 1696) propose that embryo-like Doushantuo microfossils are nonmetazoan holozoans akin to mesomycetozoeans. However, both size and preservation preclude interpretation of internal structures as nuclei. Moreover, the authors may have conflated two different populations; some specimens display a pseudoparenchymatous organization incompatible with a mesomycetozoean comparison.

The deep-water Avalon biota (about 579 to 565 million years old) is often regarded as the earliest-known fossil assemblage with macroscopic and morphologically complex life forms. It has been proposed that the rise of the Avalon biota was triggered by the oxygenation of mid-Ediacaran deep oceans. Here we report a diverse assemblage of morphologically differentiated benthic macrofossils that were preserved largely in situ as carbonaceous compressions in black shales of the Ediacaran Lantian Formation (southern Anhui Province, South China). The Lantian biota, probably older than and taxonomically distinct from the Avalon biota, suggests that morphological diversification of macroscopic eukaryotes may have occurred in the early Ediacaran Period, perhaps shortly after the Marinoan glaciation, and that the redox history of Ediacaran oceans was more complex than previously thought.

Bailey et al. propose that the Ediacaran microfossils Megasphaera and Parapandorina, previously interpreted as animal resting eggs and blastula embryos, represent Thiomargarita-like sulphide-oxidizing bacteria, claiming that this interpretation better explains their abundance and taphonomy. Here we highlight important observations that significantly weaken the authors' conclusions.

Stereoblastic embryos from the Doushantuo Formation of China exhibit occasional asynchronous cell division, with diminishing blastomere volume as cleavage proceeded. Asynchronous cell division is common in modern embryos, implying that sophisticated mechanisms for differential cell division timing and embryonic cell lineage differentiation evolved before 551 million years ago. Subcellular structures akin to organelles, coated yolk granules, or lipid vesicles occur in these embryos. Paired reniform structures within embryo cells may represent fossil evidence of cells about to undergo division. Embryos exhibit no evidence of epithelial organization, even in embryos composed of approximately 1000 cells. Many of these features are compatible with metazoans, but the absence of epithelialization is consistent only with a stem-metazoan affinity for Doushantuo embryos.

Ediacara fossils are among the oldest known macroscopic and complex life forms. Their bodyplan, ecology, and phylogenetic affinities have been controversial. On the basis of taphonomic observations, Seilacher [Seilacher, A. (1989) Lethaia 22, 229-239] proposed that the core elements of the Ediacara biota, the vendobionts, were constructed with serially or fractally arranged quilts or tube-like units. However, anatomy of quilt walls has been rarely reported, because most Ediacara fossils are preserved as casts and molds in siliciclastic rocks with inadequate morphological resolution. Here, we report an Ediacara form, uniquely preserved in situ and in three dimensions with its organic walls cast by early diagenetic calcite, from bituminous limestone of the 551- to 542-mega-annum Dengying Formation of South China. Despite diagenetic tampering, serial sections show that the Dengying form consists of biserially arranged, tube-like quilts, each with two vertical side walls, a floor, a roof, and an open distal end. Three-dimensional morphological complexity of the Dengying form excludes a microbial interpretation but is broadly consistent with vendobionts. Unlike classic frondose vendobionts sensu Seilacher, however, the Dengying form probably lacked a smooth margin and had distally open quilts. It probably lived procumbently at or near the water-sediment interface and shows evidence for substrate utilization. Despite its uncertain phylogeny, ontogeny, and functional biology, the Dengying form adds to Ediacaran biodiversity, places key constraints on the ecology and extinction of Ediacara organisms, and points to the need to explore an alternative taphonomic window for Ediacara biology.

Chuaria is one of the few globally distributed macrofossil pioneers documented in the Precambrian. It is perhaps the most controversial fossil in term of its affinity despite more than one hundred years of study. Many mutually exclusive affinities have been suggested for this frequently encountered fossil. Although often treated as a multicellular alga, this interpretation remains inconclusive because the lacking unambiguous demonstration of cellular structures. In this paper the cellular details of Chuaria are clearly revealed for the first time. The cell walls in Chuaria suggest that it is a multicellular eukaryotic alga, in agreement with the latest biogeochemical analyses. Different thicknesses of cell walls suggest primary cellular differentiation in this organism. Membrane-like structures within the cells (the first to be reported in Precambrian fossils) imply a eukaryotic nature. This study partially resolves the century-long controversy over the affinity of Chuaria, and makes Chuaria one of the few recognized multicellular eukaryotes before the Neoproterozoic glaciation. [ABSTRACT FROM AUTHOR]

Abundant well-preserved large articulated sponge fossils and isolated spicules have been reported from the Early Cambrian Hetang Formation, southern Anhui Province. This unique epifaunal fossil assemblage dominated by articulated sponge fossils is called the Xidi Sponge Fauna. The sponge fauna lived in a quiet oxygenic environment below the storm wave base. Bloom of phytoplankton and rapid sedimentation rate resulted in the deposition of the black shales. Sufficient food supply, lack of other competitors, abundant ecological niches, and demand for oxygen during early Cambrian were in favor of the diversification and evolution of large sponges in the Early Cambrian. [ABSTRACT FROM AUTHOR]

The Proterozoic witnessed the emergence and rise of early eukaryotes and Proterozoic carbonaceous compression macrofossils provide a valuable window for our understanding of this ecological expansion. Among them, the discoidal Chuaria and tomaculate Tawuia , which often co-occur in the same bedding layer, are perhaps the most common fossil forms in Proterozoic successions with extremely long temporal and broad geographical distributions. However, their phylogenetic interpretations and the relationship between them have been debated for decades, due to their simple morphologies lacking phylogenetically diagnostic features. In this study, we used an integrated application of reflected and transmitted light microscopy, scanning electron microscopy, biometric analysis, and Raman spectroscopy to characterize well-preserved carbonaceous compression macrofossils of Chuaria and Tawuia from the Tonian Liulaobei Formation in Huainan region, northern Anhui province, North China. The fossils are abundantly preserved in a ca. 1–2 cm thick homogeneous mudstone layer and can be considered to be closer to an ecological community than fossils from multiple different layers or localities. The comprehensive analysis shows that even Chuaria vesicles from the same layer may have a polyphyletic origin and three groups of Chuaria vesicles have been identified. Among them, small Chuaria vesicles with minimum diameter < 1.2 mm can be either related to the sphaeromorphic acritarch Leiosphaeridia or interpreted as multicellular aggregates. In contrast, large Chuaria vesicles with minimum diameter ≥ 1.2 mm are more comparable to the type material of Chuaria circularis from the Chuar Group and more closely related, either phylogenetically or ontogenetically, to Tawuia vesicles. This study takes a step on the path to solving the mystery of the most common and widely distributed Proterozoic macrofossil assemblage (i.e., Chuaria - Tawuia assemblage), and urges thorough and systematic evaluations to be taken on the possibility that Chuaria vesicles from the same Chuaria - Tawuia assemblages or sole Chuaria assemblages in other localities might also be polyphyletic. • Morphological and biometric features have been revealed for a Chuaria - Tawuia assemblage from the Tonian Liulaobei Formation. • Three groups of Chuaria vesicles have been identified from the same bedding layer, indicating a polyphyletic origin. • Chuaria with minimum diameter ≥ 1.2 mm are more closely related, either phylogenetically or ontogenetically, to Tawuia. • The possibility that Chuaria vesicles from other localities are polyphyletic warrants a thorough and systematic evaluation. [ABSTRACT FROM AUTHOR]

Bituminous limestone of the Ediacaran Shibantan Member of the Dengying Formation (551–539 Ma) in the Yangtze Gorges area contains a rare carbonate-hosted Ediacara-type macrofossil assemblage. This assemblage is dominated by the tubular fossil Wutubus Chen et al., 2014 and discoidal fossils, e.g., Hiemalora Fedonkin, 1982 and Aspidella Billings, 1872, but frondose organisms such as Charnia Ford, 1958, Rangea Gürich, 1929, and Arborea Glaessner and Wade, 1966 are also present. Herein, we report four species of Arborea from the Shibantan assemblage, including the type species Arborea arborea (Glaessner in Glaessner and Daily, 1959) Glaessner and Wade, 1966, Arborea denticulata new species, and two unnamed species, Arborea sp. A and Arborea sp. B. Arborea arborea is the most abundant frond in the Shibantan assemblage. Arborea denticulata n. sp. resembles Arborea arborea in general morphology but differs in its fewer primary branches and lower length/width ratio of primary branches. Arborea sp. A and Arborea sp. B are fronds with a Hiemalora-type basal attachment. Sealing by microbial mats and authigenic cementation may have played an important role in the preservation of Arborea in the Shibantan assemblage. The Shibantan material of Arborea extends the stratigraphic, ecological, and taphonomic ranges of this genus. UUID: http://zoobank.org/554f21da-5f09-4891-9deb-cbc00c41e5f1 [ABSTRACT FROM AUTHOR]

Common members of Proterozoic macrofossil assemblages usually include discs and tubes. Particularly, discoidal forms (e.g., Chuaria and abundant unnamed discs) and tubular forms (e.g., Tawuia and the worm-like annulated taxa Protoarenicola , Pararenicola , and Sinosabellidites) dominate most Tonian macrofossil assemblages. Previous work on Proterozoic materials indicated that some discoidal fossils could be detached holdfasts of co-occurring erect benthic organisms, e.g., some tubular fossils and frondose fossils, but little attempt has been made to quantify the potential relationship between the discoidal fossils and the discoidal holdfasts of tubular fossils from Tonian successions. In this study, we find biometric and chemospatial links between discoidal fossils with a central opening and worm-like annulated tubular fossils from the Tonian Jiuliqiao Formation (∼950–720 Ma) in Huainan region, northern Anhui province, North China, which supports the notion that discoidal fossils represent detached holdfasts of tubular fossils and that tubular fossils with or without a holdfast share a potential biological or ontogenic relationship. The paleoecological implication of possible holdfast coalescence (physical contact and fusion of two or more adjacent holdfasts) for Pre-Cryogenian benthic ecosystem and the evolutionary implication of this study for other Proterozoic enigmatic discoidal fossils, particularly for those with a central opening or circular ring, are discussed. Detached holdfasts and holdfast coalescence may be more common than we have thought in the Pre-Cryogenian, and the paleoecological and geobiological role of benthic algae and their holdfasts during this period is probably underestimated. Our study also highlights the adaptation of holdfast morphology to Precambrian mat-ground substrate, and provides evidence for the co-evolution of substrate and benthic organismic morphology during this period. • Biometric and chemospatial links have been revealed between the Tonian discoidal fossils and annulated tubular fossils. • Annulated tubular fossils with or without a holdfast share a potential biological or ontogenic relationship. • Detached holdfasts and holdfast coalescence may be more common than we have thought in the Pre-Cryogenian. • The paleoecological and geobiological role of benthic algae in the Pre-Cryogenian is probably underestimated. [ABSTRACT FROM AUTHOR]

• Diverse organic-walled microfossils have been revealed from the early Neoproterozoic Qinggouzi Formation in North China. • The Great Unconformity in northeastern North China represents a major depositional gap of >200 Myr. • The Great Unconformity is widespread but diachronous in the North China Craton. The Great Unconformity at the Precambrian-Cambrian boundary has been recognized on several continents and may provide critical insights into the environmental context of the Cambrian explosion. However, the geodynamic drivers, geochronological duration, and paleogeographic extent of the Great Unconformity remain unconstrained in many cases. Recently, a major depositional gap of varying magnitudes has been reported around the Precambrian-Cambrian boundary in several regions of North China, leading to the interpretation that the Great Unconformity may have been widespread but diachronous across the North China Craton. However, the magnitude of the Great Unconformity remains unknown in northeastern North China, largely because of the poor age constraints on the thick Proterozoic–Cambrian successions in this region. Here we use biostratigraphic data to constrain the depositional age of Proterozoic strata below the Great Unconformity in northeastern North China. We report a diverse organic-walled microfossil assemblage from the Qinggouzi Formation in southern Jilin Province, northeastern margin of the North China Craton. Typical late Mesoproterozoic to early Neoproterozoic microfossils, including Trachyhystrichosphaera aimika and Proterocladus antiquus , are present in Qinggouzi assemblage, providing a solid biostratigraphic constraint on the Qinggouzi Formation. Given that the overlying Shuidong Formation contains typical early Cambrian small shelly fossils, our new data indicate that the Great Unconformity in northeastern North China represents a major depositional gap of >200 Myr. Thus, the new data, along with other available biostratigraphic and geochronological data from over the world, provide robust constraints on the paleogeographic extent, chronostratigraphic duration, and diachronous nature of the Great Unconformity. [ABSTRACT FROM AUTHOR]

The Neoproterozoic Quruqtagh Group in eastern Chinese Tianshan consists of, in ascending order, the Bayisi, Zhaobishan, Altungol, Tereeken, Zhamoketi, Yukkengol, Shuiquan, and Hankalchough Formations. Diamictite units occur in the Bayisi–Altungol, Tereeken, and Hankalchough Formations. Our field observations confirm the glacial origin of the Tereeken and Hankalchough diamictites, but the glacial origin of diamictites in the Bayisi and Altungol Formations remain ambiguous. While siliciclastic strata dominate the succession, carbonate units are recognized between the diamictites and immediately atop the Tereeken and Hankalchough diamictites. Carbonates in the Altungol Formation are characterized by highly positive δ13C values (up to +10.4‰ versus PDB), comparable to those of pre-Marinoan but post-Sturtian carbonates. High-resolution sampling of the pinkish cap dolostone (ca. 10 m-thick) overlying the Tereeken diamictite shows a consistent δ13C chemostratigraphic pattern (ca. −5‰ at the base and slightly decreasing upsection) similar to that of Marinoan cap carbonates. This cap dolostone is also characterized by macropeloids similar to those in the Marinoan-age Raventhroat cap carbonate, Mackenzie Mountains. Chemostratigraphic and sedimentary features are suggestive of a Marinoan age for the Tereeken glaciation. Thus, the younger Hankalchough diamictite may represent a post-Marinoan glaciation. This interpretation is consistent with the occurrence of vendotaenid fossils in the Shuiquan Formation. The alternative interpretation—the Tereeken and Hankalchough diamictites are, respectively, Sturtian and Marinoan in age—is not consistent with the above evidence or the chemostratigraphic features of the Shuiquan Formation and the Hankalchough cap carbonate. A post-Marinoan age for the Hankalchough and other glaciogenic deposits indicates that the disappearance of Doushantuo-type acritarchs and the subsequent radiation of macroscopic animals are closely linked, in geochronological terms, with a Neoproterozoic glaciation. [Copyright &y& Elsevier]