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-Geographic context of the fossiliferous Ediacara Member in the Flinders Ranges of South Australia. Gray denotes exposure of the Pound Subgroup. Modified from Tarhan et al. (2015a).
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The Ediacara Member of the Rawnsley Quartzite of South Australia hosts some of the most ecologically and taxonomically diverse fossil assemblages of the eponymous Ediacara Biota-Earth's earliest fossil record of communities comprised of macroscopic, complex, multicellular organisms. At the National Heritage Site, Nilpena, fifteen years of systemati...
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... one of the best- exposed and most complete successions of Neoproterozoic to lower Paleozoic rocks in the world and includes the type section for the Ediacaran Period. The Ediacara Member of the Rawnsley Quartzite is the youngest Ediacaran unit in the Neoproterozoic-middle Cambrian succes- sion of the Adelaide Fold Belt of South Australia ( Fig. 1; Gehling 2000). The Ediacara Member, which is 10-300 m in thickness, is defined at its basal contact with the underlying Chace Quartzite Member of the Rawnsley Quartzite and the Bonney Sandstone by an erosional unconformity ( Counts et al. 2016). Unlike the intertidal to supratidal Chace Quartzite Member and the fluvial Bonney Sandstone, the Ediacara ...
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... 1.2), and the resulting accommodation space provided by this enabled the development of different facies. At NENP, fossils of the Ediacara Biota predominantly occur in four facies: Flat-Laminated to Linguoid-Rippled Sandstone (FLLRS), Oscillation-Rippled Sandstone (ORS), Planar-Laminated and Rip-Up Sandstone (PLRUS), and Channelized Sandstone and Sand-Breccia (CSSB) (Gehling and Droser, 2013;Droser et al., 2017;Tarhan et al., 2017;Reid et al., 2018). ...
Tribrachidium heraldicum Glaessner in Glaessner and Daily, 1959 is a triradial Ediacaran organism found in abundance within the Ediacara Member of the Flinders Ranges, South Australia. Here we report and describe a new species within the genus Tribrachidium Glaessner in Glaessner and Daily, 1959: Tribrachidium gehlingi new species from Nilpena Ediacara National Park (NENP), South Australia. Tribrachidium gehlingi n. sp. has low relief and three slightly curved, main arm-like structures that leave a conspicuous gap between the end of the arm-like structures and rim. In place of the ‘bulla’ found on T. herladicum , there are three secondary arm-like structures approximately half of the length of the main arm-like structures. Key morphological differences between the two species are statistically significantly different. Additionally, the species occur together within the same fossiliferous event horizons, indicating that the observed morphological differences are unlikely a result of taphonomy.
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... The widespread distribution of biomats during the Ediacaran and lower Paleozoic strata has played an important ecological role in seafloor colonization and ecosystem structuration (Seilacher, 1999;Tarhan et al., 2017;Cribb et al., 2019;Buatois, 2016, 2020). This includes, for instance, the replacement of Proterozoic-style biomats dominated by microorganisms exhibiting a Phanerozoic-style bioturbated mixground. ...
The rise of morphological complexity and taxonomic diversity of trace fossils during the Cambrian Period has been a prominent focus to track the evolution and diversification of early animals. Here, we present a newly described trace fossil assemblage from the lower Cambrian Le Rozel Formation in Normandy (Northwestern France) composed of the following ichnogenera: Archaeonassa, Bergaueria, Helminthoidichnites, Helminthopsis, Nereites, Psammichnites, and Treptichnus. Trace fossils are exquisitely preserved on top of strata (i.e., epirelief), and are distributed through the entire thickness of the siliciclastic succession of about 200 m. This thick sedimentary succession shows sedimentary environments with ripples generated by unidirectional current processes or by oscillatory processes, such as hummocky cross-stratification (HCS) storm facies, tidal facies with flaser stratification, and unidirectional current ripples. In addition, syneresis cracks and microbially induced sedimentary structures (MISS) suggest that the Le Rozel Formation was deposited in a shallow marine shelf environment. New U-Pb dating of detrital zircon grains suggests a late Ediacaran maximum deposition age of 549 ± 3 Ma. This dating is supplemented by the substantial preservation of the three-dimensional burrow systems (Treptichnus pedum) and the large sediment bulldozers (Nereites, Psammichnites). Collectively, our findings suggest that the trace fossils assemblage was deposited during the Terreneuvian Epoch, beneath the first archaeocyaths and the first trilobite-bearing facies from both other lower Cambrian Carteret and Saint-Jean-de-la-Rivière Formation. The ichnofauna described from the Le Rozel Formation complements the worldwide trace fossil record around this critical time of life history.
... nearshore to deltaic sandstones (Jenkins et al. 1983;Tarhan et al. 2017;McMahon et al. 2020). This depositional environment is broadly similar to that of the Kanies and lower Mara members. ...
... Indeed in the Nama assemblage, the typical preservation of trace fossils is on bed soles, not bed tops and likewise mainly bed sole surfaces of bedding planes and their counterparts preserve the White Sea Assemblage fossils of the Ediacara Mb (e.g. Tarhan et al. 2017;Droser et al. 2019). So the apparent absence of typical White Sea Assemblage fossils from the Kanies and lower Mara members may, therefore, not be significant. ...
The Nama Group, Namibia (≥550.5 to <538 million years ago, Ma), preserves one of the most diverse metazoan fossil records of the terminal Ediacaran Period. We report numerous features that may be biological in origin from the shallow marine, siliciclastic, lowermost Mara Member (older than ca. 550.5 Ma) from the Tsaus Mountains. These include forms that potentially represent body fossils, Beltanelliformis and an indeterminate juvenile uniterminal rangeomorph or arboreomorph frond, plug trace fossils, Bergaueria , as well as sedimentary surface textures, which are possibly microbially induced. These are the oldest documented macrofossils in the Nama Group. They represent taxa that persist from the Avalon or White Sea assemblages prior to the later appearance of new biota, including calcified metazoans, calcified and soft-bodied tubular taxa including all cloudinids, as well as more complex trace fossils.
Using a new age model that allows more accurate stratigraphic placement of major Ediacaran macrofossil morphogroups and taxa, we propose a re-definition of the Nama Assemblage following the practice for Phanerozoic evolutionary faunas to include only new morphogroups of soft-bodied tubular, calcified taxa and complex trace fossils, defined by first appearance of Cloudina , which postdates deposition of the Kanies and lower Mara members and first appears ca. 550 Ma and persists until at least 539 Ma.
Finally, the Tsaus Mountain environment is pristine, unspoilt by geologists and naturalists. Following World Heritage Convention, we suggest a pledge of non-destructive excavation that all future scientists should be able to make in publications of work that involve research in this area.
... The Ediacara Mb of the Rawnsley Quartzite remains poorly constrained in time but likely contemporaneous with other White Sea assemblage localities >550 Ma, and consists of a shallowing-upwards succession of up to five parasequences of shallow marine, nearshore to deltaic sandstones (Jenkins et al., 1983;Tarhan et al., 2017;McMahon et al., 2020). This depositional environment is broadly similar to that of the Kanies and lower Mara members. ...
... Ernietta) in the Nama Group (e.g.,Narbonne at al., 1997). Indeed in the Nama assemblage, the typical preservation of trace fossils is on bed soles, not bed tops, and likewise mainly bed sole surfaces of bedding planes and their counterparts preserve the White Sea Assemblage fossils of the Ediacara Mb (e.g.,Droser et al., 2019;Tarhan et al., 2017). So the apparent absence of typical White Sea Assemblage fossils from the Kanies and lower Mara members may, therefore, not be significant. ...
The Nama Group, Namibia (≥550.5 to <538 million years ago, Ma) preserves one of the most diverse metazoan fossil records of the terminal Ediacaran Period. We report numerous features that may be biological in origin from the shallow marine, siliciclastic, lowermost Mara Member (older than ca. 550.5 Ma) from the Tsaus Mountains. These include forms that potentially represent body fossils, Beltanelliformis and an indeterminate juvenile uniterminal rangeomorph or arboreomorph frond, plug trace fossils, ?Bergaueria, as well as sedimentary surface textures, which are possibly microbially-induced. These are the oldest documented macrofossils in the Nama Group. They represent taxa that persist from the Avalon or White Sea assemblages prior to the later appearance of new biota, including calcified metazoans, calcified and soft-bodied tubular taxa including all cloudinids, as well as more complex trace fossils. Using a new age model that allows more accurate stratigraphic placement of major Ediacaran macrofossil morphogroups and taxa, we propose a re-definition of the Nama Assemblage following the practice for Phanerozoic evolutionary faunas to include only new morphogroups of soft-bodied tubular, calcified taxa and complex trace fossils, defined by first appearance of Cloudina, which postdates deposition of the Kanies and lower Mara members and first appears ca. 550 Ma and persists until at least 539 Ma. Finally, the Tsaus Mountain environment is pristine, unspoilt by geologists and naturalists. Following World Heritage Convention, we suggest a pledge of non-destructive excavation that all future scientists should be able to make in publications of work that involve research in this area.
... Each bedding plane represents a single depositional event that instantaneously buried the matground and the associated macrobiota communities, resulting in the casting and molding of the smothered communities on the base of the burial sand body. The persistence of these bedforms as discrete, successive, and texturally homogenous bedding planes through diagenesis is attributed to the organic barrier created by pervasive organic matgrounds along with the early-initiating precipitation of authigenic silica cements enabled by the high silica saturation state of Ediacaran oceans (Tarhan et al., 2016(Tarhan et al., ,2017Slagter et al., 2021Slagter et al., ,2022. ...
... These bedding planes provide a dataset of multiple populations of Aulozoon that are ecologically and environmentally contextualized and represent preservation under varying substrate conditions (i.e., organic surface development and grain size) as well as varying energetic conditions (i.e., facies). Aulozoon is found in two facies at NENP: the Oscillation-Rippled Sandstone (ORS) facies and the Planar Laminated and Rip-Up Sandstone (PLRUS) facies Tarhan et al., 2017). The ORS facies records deposition between fair-weather and storm wave base and is comprised of thinly bedded, rippled fine-to coarsegrained feldspathic quartzarenite Tarhan et al., 2017). ...
... Aulozoon is found in two facies at NENP: the Oscillation-Rippled Sandstone (ORS) facies and the Planar Laminated and Rip-Up Sandstone (PLRUS) facies Tarhan et al., 2017). The ORS facies records deposition between fair-weather and storm wave base and is comprised of thinly bedded, rippled fine-to coarsegrained feldspathic quartzarenite Tarhan et al., 2017). The PLRUS facies represents upper sub-wave base canyon fill deposits and is characterized by laterally continuous, planar-laminated fine-grained quartzarenite beds Tarhan et al., 2017). ...
... At NENP, fossiliferous surfaces have been excavated from the Oscillation-Rippled Sandstone Facies (ORS) and the Planar-Laminated and Rip-Up Sandstone Facies (PLRUS; Gehling and Droser 2013;Droser et al. 2017Droser et al. , 2019Tarhan et al. 2017). The ORS Facies is characterized by submillimeter-to centimeter-thick, rippled, fineto coarse-grained quartz sandstones interpreted to have been deposited under oscillatory and combined flow between fair-weather-and storm-wave base Droser et al. 2019). ...
The spatial distribution of in situ sessile organisms, including those from the fossil record, provides information about life histories, such as possible dispersal and/or settlement mechanisms, and how taxa interact with one another and their local environments. At Nilpena Ediacara National Park (NENP), South Australia, the exquisite preservation and excavation of 33 fossiliferous bedding planes from the Ediacara Member of the Rawnsley Quartzite reveals in situ communities of the Ediacara Biota. Here, the spatial distributions of three relatively common taxa, Tribrachidium, Rugoconites, and Obamus, occurring on excavated surfaces were analyzed using spatial point pattern analysis. Tribrachidium have a variable spatial distribution, implying that settlement or post-settlement conditions/preferences had an effect on populations. Rugoconites display aggregation, possibly related to their reproductive methods in combination with settlement location availability at the time of dispersal and/or settlement. Additionally, post-settlement environmental controls could have affected Rugoconites on other surfaces, resulting in lower populations and densities. Both Tribrachidium and Rugoconites also commonly occur as individuals or in low numbers on a number of beds, thus constraining possible reproductive strategies and environ-mental/substrate preferences. The distribution of Obamus is consistent with selective settlement, aggregat-ing near conspecifics and on substrates of mature microbial mat. This dispersal process is the first example of substrate-selective dispersal among the Ediacara Biota, thus making Obamus similar to numerous modern sessile invertebrates with similar dispersal and settlement strategies.
... Drab-haloed threads down into red paleosols below Dickinsonia [6,63] are Prasinema: traces of mycelia or rope-forming cyanobacteria common in paleosols [121][122][123]. These subvertical drab threads disturb bedding and create massive red beds in the field and in thin sections [48], unlike the laminated microbial mat interpretation of the same beds [2,124]. Ediacaran "Mattressland" vendobionts of red beds [120] may be contrasted with Ediacaran grey stromatolitic carbonates and shaley turbidites with marine tubular fossils such as Gaojianshania, Conotubus, Cloudina, and Namacalathus of Ediacaran "Wormworld" [125][126][127]. ...
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.
... Such matgrounds played a pivotal role in rendering the seafloor habitable for the Ediacara Biota, by stabilizing seafloor sediments and providing food and potentially oxygen (e.g., Seilacher, 1999;Gingras et al., 2011;Droser et al., 2017;Gehling and Droser, 2018;Evans et al., 2019;Evans et al., 2020). Furthermore, the organically-stabilized substrate also shaped the sedimentologic and stratigraphic expression of Ediacaran successions by binding sediment, which inhibited reworking and erosion and facilitated the capture of a complete sedimentary and stratigraphic record (Noffke, 2009;Tarhan et al., 2017). ...
... At the Nilpena Ediacara National Park (NENP), excavation of 40 bedding planes, 33 of which preserve >10 individual macroscopic body fossils, reveals an unprecedented abundance and diversity of in situ macroorganism communities and associated microbial mats. Many of the bedding-plane features that are central to defining MISS and TOS (e.g., preservational variability, bed-scale diversity, associated macrobiota, grain size, mineralogy, chemical composition, and sedimentary structures) have previously been described (e.g., Bottjer et al., 2007;Bouougri and Porada, 2007;Carbone and Narbonne, 2014;Corenbilt et al., 2019;Elliott et al., 2011;Hill et al., 2016;Kumar and Ahmad, 2014;Laflamme et al., 2012;Liu et al., 2013;Nettle et al., 2014;Nofke, 2015;Noffke et al., 2002;Noffke, 2009;Sarkar et al., 2008, Sarkar et al., 2016Tarhan et al., 2017;Vago et al., 2017). Here our aim is to use this record to develop criteria to evaluate the maturity or extent of growth of Ediacaran matgrounds and, using these characteristics, to examine the relationship between mat type and maturity and Ediacara Biota community structure. ...
... Scale bars = 50 cm. (A) Modified from Tarhan et al. (2017). ...
In the absence of complex, bioturbating organisms, the seafloor during the Precambrian was covered in widespread organic matgrounds. The greatest diversity and complexity of organic mat textures occur in the Ediacaran fossil record as exemplified by the Ediacara Member of the Rawnsley Quartzite, which crops out in and around the Flinders Ranges, South Australia. This succession unambiguously demonstrates that heterogenous mats coexisted with and were central to the ecology and biology of the Ediacara Biota. Excavation of 33 fossiliferous beds with varying types and extents of organosedimentary surface textures provide the opportunity to utilize this record to develop criteria to evaluate the maturity or extent of growth of Ediacaran matgrounds and, using these characteristics, to examine the relationship between mat type, mat maturity and Ediacara Biota community structure. Based on the assumption that mat maturity represents an indicator of the duration of time between burial events, we can test predictions about the relationship between mat maturity and community development. We find that mat maturity, rather than the mat type itself, more strongly influenced the distribution of taxa and the development of Ediacara macroorganism communities. Using a ranked Mat Maturity Index, we find that although density of macroscopic body fossils and genus diversity correlate with mat maturity, evenness does not. We additionally find that the sessile taxa Obamus and Coronacollina are restricted to surfaces with mature mats whereas all other Ediacaran macrobiota show no connection to mat occurrence and maturity. However, we do observe that large Dickinsonia are more likely to occur on surfaces recording mature matgrounds. The exceptional record of mat surfaces preserved in the Flinders Ranges area demonstrates that, in addition to the apparent ecological role played by mat surfaces in Ediacaran communities, they were also likely a significant component of the Ediacara Member biomass and were integral to community function.
... These deposits lie below a basal Cambrian disconformity and, based on similar taxa identified from the White Sea Region of Russia, are interpreted to be between 560 and 551 Ma old (Gehling 1999;Grazhdankin 2014;Boag et al. 2016). The Ediacara Member consists of siliciclastic, predominately sandstone event beds with fossils found in deposits representing a range of shallowmarine environments (Gehling 2000;Gehling and Droser 2013;Tarhan et al. 2017;Reid et al. 2020;McMahon et al. 2020). Fossils, including Dickinsonia, are typically preserved as negative hyporelief external molds, representing impressions of the top surface in overlying sandstone beds (Gehling 1999;Tarhan et al. 2016). ...
... Dickinsonia occurs on 37 of 39 beds at Nilpena, including TB-ARB. It has been identified in the four fossilbearing facies identified by Tarhan et al. (2017) of the Ediacara Member in association with a diversity of other macroscopic taxa and textured organic surfaces-representing the preservation of organic mats, ubiquitous on the Ediacaran seafloor Droser 2009, 2013). ...
Constraining patterns of growth using directly observable and quantifiable characteristics can reveal a wealth of information regarding the biology of the Ediacara biota—the oldest macroscopic, complex community-forming organisms in the fossil record. However, these rely on individuals captured at an instant in time at various growth stages, and so different interpretations can be derived from the same material. Here we leverage newly discovered and well-preserved Dickinsonia costata Sprigg, 1947 from South Australia, combined with hundreds of previously described specimens, to test competing hypotheses for the location of module addition. We find considerable variation in the relationship between the total number of modules and body size that cannot be explained solely by expansion and contraction of individuals. Patterns derived assuming new modules differentiated at the anterior result in numerous examples in which the oldest module(s) must decrease in size with overall growth, potentially falsifying this hypothesis. Observed polarity as well as the consistent posterior location of defects and indentations support module formation at this end in D. costata . Regardless, changes in repeated units with growth share similarities with those regulated by morphogen gradients in metazoans today, suggesting that these genetic pathways were operating in Ediacaran animals.
... Perhaps most significantly, a trace fossil record of complex horizontal burrows and trails appears from~560 Ma, likely documenting the emergence of a bilaterian benthos (Martin et al. 2000;Jensen, 2003;Chen et al. 2013Chen et al. , 2019Budd, 2015;Budd & Jensen, 2017). These simple trace fossils are consistently found in association with bedding planes exhibiting microbial mat textures, and have been interpreted as representing a variety of mat-exploiting behaviours (Buatois et al. 2014;Meyer et al. 2014;Tarhan et al. 2017;Ivantsov et al. 2019b). Together, these lines of evidence point to a characteristic Ediacaran matground ecology which appears to have persisted into the early Cambrian Fortunian (Buatois et al. 2014;Laing et al. 2019). ...
Here we present a detailed accounting of organic microfossils from late Ediacaran sediments of Finland, from the island of Hailuoto (northwest Finnish coast), and the Saarijärvi meteorite impact structure (~170 km northeast of Hailuoto, mainland Finland). Fossils were recovered from fine-grained thermally immature mudstones and siltstones and are preserved in exquisite detail. The majority of recovered forms are sourced from filamentous prokaryotic and protistan-grade organisms forming interwoven microbial mats. Flattened Nostoc-ball-like masses of bundled Siphonophycus filaments are abundant, alongside Rugosoopsis and Palaeolyngbya of probable cyanobacterial origin. Acritarchs include Chuaria, Leiosphaeridia, Symplassosphaeridium and Synsphaeridium. Significantly, rare spine-shaped sclerites of bilaterian origin were recovered, providing new evidence for a nascent bilaterian fauna in the terminal Ediacaran. These findings offer a direct body-fossil insight into Ediacaran mat-forming microbial communities, and demonstrate that alongside trace fossils, detection of a bilaterian fauna prior to the Cambrian might also be sought among the emerging record of small carbonaceous fossils (SCFs).
