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Horizontal surface traces from the Fermeuse Formation, Ferryland (Newfoundland, Canada), and their place within the Late Ediacaran ichnological revolution

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Abstract

In recent years, multiple studies have emerged that claim to document metazoan locomotion within the late Ediacaran Period, between ~585 and 541 Ma. Most of this evidence is limited to simple horizontal burrows and surface trace fossils, but these have undergone little in the way of critical analysis to determine whether they truly result from metazoan activity. Here we review the evidence for metazoan locomotion from Avalonian biotic assemblages, and demonstrate that locomotory behaviour, largely in the form of horizontal surface trails, may not be as rare in those regions as has previously been considered. Furthermore, Avalonian trace fossils likely predate claims of metazoan locomotion from most other global localities. New evidence for horizontal surface traces from rocks of the Fermeuse Formation, ~560 Ma, is also presented. When discussed in the context of the global Ediacaran to Cambrian ichnofossil record, it becomes evident that a gradual increase in abundance of horizontal surface locomotion is observed through the late Ediacaran Period. Vertical movement within the sediment appears ~560 Ma, with evidence for organisms forming equilibrium traces in response to low levels of sediment input. Evidence for extensive vertical burrowing and pervasive bioturbation is not yet convincingly demonstrated until at or near the Ediacaran–Cambrian boundary, ~541 Ma.

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... Further surface traces have since been found in the younger, shallower, Fermeuse Formation (e.g. Menon et al., 2013; Liu and McIlroy, 2015), with some demonstrated to be associated with the type-morph of Aspidella terranovica (Menon et al., 2013 ). Importantly, several impressions within the Fermeuse Formation appear to truncate sedimentary laminae in vertical section, and have thus been interpreted as vertical equilibration traces formed by organisms shuffling upwards through the sediment in response to small sedimentary influxes (Menon et al., 2013 ), a suggestion not too dissimilar to that made by MacGabhann (2007, p. 303). ...
... Rangeomorphs, arboreomorph/frondomorphs, and the majority of the miscellaneous taxa abundant on these bedding planes are still interpreted as sessile and immotile. Furthermore, evidence for locomotion in other Avalonian Ediacaran localities (Fig. 1B) remains scarce, with a handful of surface impressions from Carmarthenshire (Cope and Bevins, 1993), and possible circular depressions from the Long Mynd (McIlroy et al., 2005), being the only other plausible examples (Liu and McIlroy, 2015). Movement remains one of the key lines of evidence for the presence of metazoans in the Neoproterozoic, and late Ediacaran ichnology is a rapidly expanding field (reviewed in Liu and McIlroy, 2015). ...
... Furthermore, evidence for locomotion in other Avalonian Ediacaran localities (Fig. 1B) remains scarce, with a handful of surface impressions from Carmarthenshire (Cope and Bevins, 1993), and possible circular depressions from the Long Mynd (McIlroy et al., 2005), being the only other plausible examples (Liu and McIlroy, 2015). Movement remains one of the key lines of evidence for the presence of metazoans in the Neoproterozoic, and late Ediacaran ichnology is a rapidly expanding field (reviewed in Liu and McIlroy, 2015). Evidence for additional interactions between taxa would be valuable in determining levels of ecological complexity within these ecosystems. ...
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Ediacaran macrofossils from the Avalon Terrane (primarily eastern Newfoundland and the central UK) record some of the earliest large and complex multicellular organisms on Earth. Perhaps the greatest unknown regarding these fossils is their relevance to the early evolutionary history of the Kingdom Animalia. In recent years, new data and discoveries have revealed insights into Ediacaran paleobiology, taxonomic relationships, paleoecology and taphonomy, significantly refining our understanding of Avalonian ecosystems. Here, we summarise recent observational and quantitative studies, and their bearing on the current understanding of Avalonian benthic marine ecosystems. A review of existing knowledge of the biological composition of Avalonian marine assemblages demonstrates that they record densely-populated ecosystems inhabited by a diverse range of organisms, likely representing multiple biological Kingdoms. Appreciation of this diversity, and of the complexities it introduces to paleoecological studies, is vital when considering the relationship between macroevolution and contemporaneous climatic, tectonic and geochemical events. We then summarise current understanding of Avalonian paleoecology. Studies into locomotion, reproduction, feeding strategies, and community structure and succession reveal that these ecosystems were considerably different to Phanerozoic settings. Furthermore, we suggest that Avalonian ecosystems witnessed the appearance of novel nutrient sources, offering new opportunities and niches for benthic organisms. The suggestion that the numerically dominant rangeomorphs were osmotrophic is reviewed and appraised in light of geochemical, morphological, and biological information. Finally, the use of modern ecological metrics in the study of Ediacaran fossil assemblages is assessed. Concerns regarding the interpretation of paleoecological data are outlined in light of current taphonomic and sedimentological understanding, and these cast doubt on previous suggestions that the Avalonian assemblages were largely composed of metazoans. Nevertheless, we emphasise that if treated with necessary caution, paleoecological data can play a significant role in assisting efforts to determine the biological affinities of late Ediacaran macroscopic organisms.
... Personally observed specimens of palaeopascichnid fossils were collected from outcrops and closely localized float of the the East European Platform. Other specimens of palaeopascichnid-like fossils were incorporated into our dataset using published photographs from Newfoundland (Narbonne et al. 1987;Gehling et al. 2000;Liu & McIlroy 2015;Hawco et al. 2019), Wales (Cope, 1982;Liu & McIlroy, 2015), Norway (McIlroy & Brasier, 2016;Jensen et al. 2018), the Transdniester Podolia of Ukraine (Palij, 1976;Palij et al. 1979;Fedonkin, 1983Fedonkin, , 1985Fedonkin, , 1990Martyshin, 2012), the Arkhangelsk region of Russia (Chistyakov et al. 1984), the Uchur-Maya Basin of Eastern Siberia (Ivantsov, 2017), Australia (Glaessner, 1969;Jenkins, 1995;Haines, 2000;Gehling et al. 2005;Gehling & Droser, 2009), South China (Wan et al. 2014) and India (Parcha & Pandey, 2011). The studied specimens are well preserved, with clear edges in various sedimentary rocks as epi-and hypo-relief fossils. ...
... Personally observed specimens of palaeopascichnid fossils were collected from outcrops and closely localized float of the the East European Platform. Other specimens of palaeopascichnid-like fossils were incorporated into our dataset using published photographs from Newfoundland (Narbonne et al. 1987;Gehling et al. 2000;Liu & McIlroy 2015;Hawco et al. 2019), Wales (Cope, 1982;Liu & McIlroy, 2015), Norway (McIlroy & Brasier, 2016;Jensen et al. 2018), the Transdniester Podolia of Ukraine (Palij, 1976;Palij et al. 1979;Fedonkin, 1983Fedonkin, , 1985Fedonkin, , 1990Martyshin, 2012), the Arkhangelsk region of Russia (Chistyakov et al. 1984), the Uchur-Maya Basin of Eastern Siberia (Ivantsov, 2017), Australia (Glaessner, 1969;Jenkins, 1995;Haines, 2000;Gehling et al. 2005;Gehling & Droser, 2009), South China (Wan et al. 2014) and India (Parcha & Pandey, 2011). The studied specimens are well preserved, with clear edges in various sedimentary rocks as epi-and hypo-relief fossils. ...
Article
Palaeopascichnida is a problematic group of extinct organisms that is globally distributed in Ediacaran sequences of Avalonia, Baltica, Siberia, South China and Australia. The fossils related to Palaeopascichnida consist of serially or cluster-like arranged, millimetre-to centimetre-scale globular or allantoid chambers, which are characterized by substantial differences in preservation , leading to no consistent diagnosis for these organisms. Here we integrate morphometric variation, stratigraphic distribution and habitat settings of more than 1200 specimens from all known fossil localities. The results of the morphological analysis demonstrate variation in chamber shape and size, and allow us to recognize six valid species within the group. Statistical analysis of the specimen distribution with respect to sedimentary environments indicates a significant difference in palaeoecological settings between species, making a significant contribution to the evolution and systematic palaeontology of these problematic organisms and perspective on their use in Neoproterozoic biostratigraphy. Our revision and systematic study sheds new light on one of the least studied groups of the late Ediacaran biota.
... Based on these uncertainties, the Fermeuse Formation of Newfoundland (approx. 560 Ma) has become a key unit to detect ichnological evidence in the Avalon assemblage [102,103]. The close association and apparent intergradations of structures described as trace fossils from this unit [103] with the body fossil Palaeopascichnus suggest that these structures may represent a continuum of taphonomic variants of this body fossil [87]. ...
... 560 Ma) has become a key unit to detect ichnological evidence in the Avalon assemblage [102,103]. The close association and apparent intergradations of structures described as trace fossils from this unit [103] with the body fossil Palaeopascichnus suggest that these structures may represent a continuum of taphonomic variants of this body fossil [87]. Interestingly, other structures in the same outcrop, specifically crescentic horizontal structures connected with Aspidella-discs and vertical equilibrium structures [102], display morphologic features that can be explained in terms of animal-substrate interactions. ...
Article
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... These discoveries provided a search image for Ediacaran researchers that presaged a considerable increase in the recognition of late Ediacaran trace fossils worldwide (e.g. Chen et al. 2013;Carbone & Narbonne 2014;Macdonald et al. 2014; see also Liu & McIlroy 2015), providing some of the strongest evidence for the presence of motile metazoans among the largely sessile Ediacaran macro-organisms. However, Martin was wary of accepting all claims for complex metazoan movement or feeding, staying true to his belief that the null hypothesis must first be rejected before considering more ground-breaking claims (Brasier 2015). ...
Article
Martin Brasier's work spanned almost the entire geological column, but the origin of animals and the nature of the Cambrian explosion were areas of particular interest to him. Martin adopted a holistic approach to the study of these topics that considered the interplay between multiple geological and biological phenomena and he sought to interpret the fossil record within the broad context of geological, biogeochemical and ecological changes in the Earth system. Here we summarize Martin's main contributions to this area of research and assess the impact of his findings on the development of this field.
... These discoveries provided a search image for Ediacaran researchers that presaged a considerable increase in the recognition of late Ediacaran trace fossils worldwide (e.g. Chen et al. 2013;Carbone & Narbonne 2014;Macdonald et al. 2014; see also Liu & McIlroy 2015), providing some of the strongest evidence for the presence of motile metazoans among the largely sessile Ediacaran macro-organisms. However, Martin was wary of accepting all claims for complex metazoan movement or feeding, staying true to his belief that the null hypothesis must first be rejected before considering more ground-breaking claims (Brasier 2015). ...
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Martin Brasier's work spanned almost the entire geological column, but the origin of animals and the nature of the Cambrian Explosion were areas of particular interest. Martin adopted a holistic approach to the study of these topics that considered the interplay between multiple geological and biological phenomena, and sought to interpret the fossil record within the broad context of geological, biogeochemical, and ecological changes in the Earth system. Here we summarize Martin's main contributions in this area, and assess the impact of his findings on the development of this field.
... We would like to add in support of our discussion of Haootia that strata of similar age in Newfoundland also contain rare fossilized surface locomotion trails that are considered to have formed by contractile activities associated with a cnidarian body plan [3][4][5][6]. We have hitherto found no evidence that the basal disc of Haootia could contract or move, but having two independent lines of evidence for the presence of organisms with contractile tissues in the Ediacaran makes a more compelling case for the presence of cnidarian-grade organisms [1]. ...
... We would like to add in support of our discussion of Haootia that strata of similar age in Newfoundland also contain rare fossilized surface locomotion trails that are considered to have formed by contractile activities associated with a cnidarian body plan [3][4][5][6]. We have hitherto found no evidence that the basal disc of Haootia could contract or move, but having two independent lines of evidence for the presence of organisms with contractile tissues in the Ediacaran makes a more compelling case for the presence of cnidarian-grade organisms [1]. ...
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Chapter
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The morphology and stratigraphic distribution of Harlaniella podolica Sokolov, 1972 and H. ingriana Ivantsov, sp. nov. were investigated using the collection of impressions sampled recently in Upper Vendian sections of Russia (southeastern White Sea region) and Ukraine (Podoliya). These fossils, which were previously considered as representing coprolites or grazing or locomotion traces, are interpreted as internal casts and impressions of fragments of tubes of initially organic composition. Streptichnus narbonnei Jensen et Runnegar, 2005 from Vendian-Cambrian boundary strata of Namibia are also attributed to this group. It is assumed that the tubes are similar to remains of the algal genera Vendotaenia Gnilovskaya, 1971 from Vendian deposits of the East European Platform and Liulingjitaenia Chen et Xiao, 1992 from Sinian sections of China.
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The rapid appearance of bilaterian clades at the beginning of the Phanerozoic is one of the most intriguing topics in macroevolution. However, the complex feedbacks between diversification and ecological interactions are still poorly understood. Here, we show that a systematic and comprehensive analysis of the trace-fossil record of the Ediacaran-Cambrian transition indicates that body-plan diversification and ecological structuring were decoupled. The appearance of a wide repertoire of behavioural strategies and body plans occurred by the Fortunian. However, a major shift in benthic ecological structure, recording the establishment of a suspension-feeder infauna, increased complexity of the trophic web, and coupling of benthos and plankton took place during Cambrian Stage 2. Both phases were accompanied by different styles of ecosystem engineering, but only the second one resulted in the establishment of the Phanerozoic-style ecology. In turn, the suspension-feeding infauna may have been the ecological drivers of a further diversification of deposit-feeding strategies by Cambrian Stage 3, favouring an ecological spillover scenario. Trace-fossil information strongly supports the Cambrian explosion, but allows for a short time of phylogenetic fuse during the terminal Ediacaran-Fortunian.
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Ediacaran trace fossils are becoming an increasingly less common component of the total Precambrian fossil record as structures previously interpreted as trace fossils are reinterpreted as body fossils by utilizing qualitative criteria. Two morphotypes, Form E and Form F of Glaessner (1969), interpreted as trace fossils from the Ediacara Member of the Rawnsley Quartzite in South Australia are shown here to be body fossils of a single, previously unidentified tubular constructional morphology formally described herein as Somatohelix sinuosus n. gen. n. sp. S. sinuosus is 2—7 mm wide and 3—14 cm long and is preserved as sinusoidal casts and molds on the base of beds. Well-preserved examples of this fossil preserve distinct body fossil traits such as folding, current alignment, and potential attachment to holdfasts. Nearly 200 specimens of this fossil have been documented from reconstructed bedding surfaces within the Ediacara Member. When viewed in isolated hand sample, many of these specimens resemble ichnofossils. However, the ability to view large quantities of reassembled and successive bedding surfaces within specific outcrops of the Ediacara Member provides a new perspective, revealing that isolated specimens of rectilinear grooves on bed bases are not trace fossils but are poorly preserved specimens of S. sinuosus. Variation in the quality and style of preservation of S. sinuosus on a single surface and the few distinct characteristics preserved within this relatively indistinct fossil also provides the necessary data required to define a taphonomic gradient for this fossil. Armed with this information, structures which have been problematic in the past can now be confidently identified as S. sinuosus based on morphological criteria. This suggests that the original organism that produced this fossil was a widespread and abundant component of the Ediacaran ecosystem.
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Avalonia is a terrane that occupied a position peripheral to Gondwana in the Neoproterozoic and early Paleozoic, and was transferred to Laurentia by the Late Ordovician. There is fragmentary evidence of early arc (ca. 780 to 660 Ma) magmatism, although it is unclear whether this represents continuous or episodic subduction. This was followed by the main arc phase from 630 to 590 Ma, which produced calc-alkalic volcanic and plutonic rocks and volcaniclastic rocks deposited in backarc basins. Pb-Pb isotopic data support previous interpretations that Avalonia was peripheral to the Amazon craton at this time. Neodymium isotopic signatures suggest that subduction polarity was to the northwest (present coordinates), which implies a 180° rotation of Avalonia prior to accretion with Laurentia. From 590 to 540 Ma, a transition from an arc to a transtensional intracontinental environment occurred diachronously from New England to the British Isles. Comparison with Cenozoic analogs suggest this can be attributed to collision of the margin with an oceanic ridge, and progressive generation of a continental transform fault as the triple point migrated along the Gondwanan margin, in a manner similar to the generation of the modern San Andreas fault system. This model also explains the change in kinematics along major faults active at this time, from sinistral to dextral and structural inversion of backarc basins.
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Metazoan trace fossils from the Upper Vendian are preserved together with remains of corresponding organisms. The traces belong to “Vendobionta”, representing the Precambrian phylum Proarticulata and to a presumably trochophoran animal Kimberella quadrata. These organisms fed on microbial mats, which preserved fossil traces. Impressions of the mat surface structures, traces, and bodies of animals are preserved in marine terrigenous sediments on the basal surfaces of sandstone beds. Proarticulata grazing traces are represented by groups and chains of impressions left by the ventral side of a body or its central and posterior parts. Kimberella traces are represented by long ridges united into bundles, fans, and chains of fans. All these traces were largely formed mechanically, i.e., by mat scratching with cilia (Proarticulata) or teeth (Kimberella). Proarticulata representatives destroyed only a thin upper layer of the mat, while Kimberella could possibly scratch the mat through its entire thickness or even tear off pieces from it.
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Ediacaran fossils are taphonomically similar to impressions of fossil plants common in quartz sandstones, and the relief of the fossils suggests that they were as resistant to compaction during burial as some kinds of Pennsylvanian tree trunks. Fossils of jellyfish are known from siderite nodules and fine-grained limestone, and even in these compaction-resistant media were more compressed during burial than were the Vendobionta. Vendobionta were constructed of materials that responded to burial compaction in a way intermediate between conifer and lycopsid logs. This comparative taphonomic study thus falsifies the concept of Vendobionta as thin soft-bodied creatures such as worms and jellyfish. Lichens, with their structural chitin, present a viable model for the observed preservational style of Vendobionta, as well as for a variety of other features that now can be reassessed from this new perspective. The diversity of Ediacaran body plans can be compared with the variety of form in fungi, algae, and lichens. The large size (ca. 1 m) of some Ediacaran fossils is reasonable for sessile photosynthetic symbioses, and much bigger than associated burrows of metazoans not preserved. Microscopic tubular structures and darkly pigmented cells in permineralized late Precambrian fossils from Namibia and China are also compatible with interpretation as lichens. The presumed marine habitat of Ediacaran fossils is not crucial to interpretation as lichens, because fungi and lichens live in the sea as well as on land.
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—The bulk of Neoproterozoic trace fossils can be interpreted as horizontal creeping trails produced by minute vermiform,organisms moving,on or just beneath the seafloor or under algal mats. We have investigated the formation of trails by living cnidarians and platyhelminths that creep by cilia on mucus ribbons. These relatively simple metazoans,produce trails that are similar in size and morphology to some Neoproterozoic traces, owing to the entrainment of sediment with- in their mucus trails. Thus a mucociliary locomotory system provides sufficient means to form some types of Neoproterozoic traces. It follows that the body architectures of the Neoproterozoic trace-makers may have been quite simple, though complex bodyplans are, of course, not ruled out. Thus, the use of Neoproterozoic trace fossils to constrain the time of origin of bilaterians or of any crown-group bilaterian taxon remains questionable. Allen G. Collins, Jere H. Lipps, and James W, Valentine. Department of Integrative Biology and Museum
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Abstarct The paper discusses a group of the Late Vendian fossils supposedly related to mollusks. The fossils include imprints with some anatomical characteristics of mollusks, traces resembling scratch marks left by radula, and structures resembling soft shells. Kimberella quadrata, which is represented by all the above kinds of fossils was most likely a trochophore animal of a pre-molluscan evolutionary stage. Remains of Armillifera parva and Solza margarita only slightly resemble shells, and in the absence of the knowledge on the soft body of these animals there are no enongh evidences affiliate them with mollusks.
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Functional, constructional, and preservational criteria led to a reinterpretation of seemingly complex trace fossils and the majority of assumed metazoan body fossils from Vendian lagerstatten. In the new scenario, Ediacaran biota were dominated by procaryote biomats and giant protozoa (Xenophyophoria and Vendobionta), which developed a great variety of shapes and lifestyles in the climatically controlled "golden age" that followed the Marinoan snowball earth. Contemporary metazoans (sponges; polyps; soft-bodied mollusks; possible echinoderms; worm-like burrowers) were adapted to this non-uniformitarian environment, but they remained scarce and relatively small. Some phyla (arthropods, brachiopods) appear to have still been absent. Our study also accentuates the Cambrian Explosion, which put an end to the peaceful "Garden of Ediacara". Not only did the former rulers become extinct or restricted to less favorable environments, but the radiation of metazoan phyla was also accompanied by an ecological revolution that established a new and more dangerous world, which persists to the present day.
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Palaeomagnetic and petromagnetic studies were carried out in two sections of the Late Vendian–Early Cambrian rocks in the southeastern White Sea region. Ninety meters of the Zolotitsa River section (350 oriented lump samples from the outcrops) and 420 m of core samples from the Verkhotina Hole (443 samples) were studied. Two absolute age values are available for the lower part of the Zolotitsa River section: 550±4.6 Ma and 550±5.3 Ma. These ages were determined using zircons from the volcanic rock interlayers. The rocks investigated in this study are characterized by the low anisotropy of magnetic susceptibility, by the absence of any predominant directions of the half-axes of the ellipsoids of anisotropy, and by the planar type of the latter. The main carrier of natural remanent magnetization (NRM) is hematite in all rocks, magnetite being found occasionally in gray rocks. The detailed stepwise thermal demagnetization of the samples proved the multicomponent composition of the rocks. The low-and medium-temperature components resulted from the demagnetization of the rocks during various interval of geologic time. The high-temperature component is characterized by the positive tests of folding, reversal, and correlation, hence being a primary one. Variations of its direction along the rock sequence were used in this study to identify 27 zones of direct and 28 zones of reversed polarity for the total amount of the rocks investigated in this study. The most reliable results were used to plot the alternative trajectory of the Baltic palaeomagnetic pole migration for the Vendian time and to reconstruct the palaeogeographic Baltic position for that time. A new method was offered and tested for orienting borehole samples in space. Its application was found to produce the high convergence of the results, both in the case of the natural outcrops and borehole samples.
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The 2.0–1.8-billion-year-old Stirling Range Formation in southwestern Australia preserves the deposits of a siliciclastic shoreline formed under the influence of storms, longshore currents, and tidal currents. Sandstones contain a megascopic fossil biota represented by discoidal fossils similar to the Ediacaran Aspidella Billings, 1872, as well as ridge pairs preserved in positive hyporelief on the soles of channel-fill sandstones bounded by mud drapes. The ridges run parallel or nearly parallel for most of their length, meeting in a closed loop at one end and opening with a slight divergence at the opposite end. The ridges are interpreted as casts of sediment-laden mucus strings formed by the movement of multicellular or syncytial organisms along a muddy surface. The taxa Myxomitodes stirlingensis n. igen., n. isp., are introduced for these traces. The Stirling biota was roughly coeval with other presumed multicellular eukaryotes appearing after a long period of profound environmental changes involving a rise in ambient oxygen levels, similar to that which preceded the Cambrian explosion. The failure of multicellular life to diversify during most of the Proterozoic may be due to environmental constraints related to the comparatively low level of oxidation of the world oceans.
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Ediacaran body fossils and trace fossils occur sporadically throughout more than one kilometre of strata in the upper part of the Windermere Supergroup in the western Northwest Territories of Canada. The Sekwi Brook biota lived in a deep-water, basin slope setting below storm wave-base. Most of the body fossils probably represent benthic polypoid and frond-like organisms. The body fossil assemblage is broadly similar to that described from correlative shallow shelf deposits in the Wernecke Mountains, Flinders Ranges and Russian Platform. The trace fossil assemblage is dominated by simple and irregularly meandering burrows, but contains some patterned meanders typical of the Nereites ichnofacies. The occurrence of this relatively diverse, mainly deep-water assemblage of benthic body fossils and infaunal burrows indicates that the initial radiation of metazoans extended to the deep sea, and that some aspects of Phanerozoic-style marine ecosystems were initiated during the earliest stages of metazoan evolution. -from Authors
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The Ediacaran fauna of Charnwood Forest is reviewed and several new forms are formally named and described, including a complex colonial form Bradgatia linfordensis and three new medusoid genera and species, Ivesia lobata, Shepshedia palmata and Blackbrookia oaksi. A new medusoid species Cyclomedusa cliffi is described. The frondose fossil Charnia grandis is recorded from Charnwood Forest for the first time. Three trails are also noted. -Authors
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Trace fossils record the behavior of animals at the very spot where they lived millions of years ago. Their growing interest derives from the intimate connection between ichnology and sedimentology and their combined relevance for paleoenvironmental reconstructions, basin analysis, and petroleum exploration. This definitive textbook by a renowned field observer and analyst of trace fossils concentrates on the most distinctive examples, mostly made by infaunal invertebrates in originally soft sediments. It covers the whole geologic column and ranges from deep-sea to shallow-marine and continental environments. Seilacher's Trace Fossil Analysis is designed to foster interpretative skills using the author's own iconic drawings. They are thematically grouped in 75 plates that form the core for the descriptive text and annotated references. A glossary of ichnological terms is also provided.
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Patterns of origination, evolution, and extinction of early animal life on this planet are largely interpreted from the fossils of the Precambrian soft-bodied Ediacara Biota, spanning nearly 40 m.y. of the terminal Ediacaran period. Localities containing these fossils are loosely considered as part of either the Avalon, White Sea, or Nama Associations. These associations have been interpreted to have temporal, paleobiogeographic, preservational, and/or paleoenvironmental signifi -cance. Surprisingly, elements of all three associations occur within the Ediacara Member of the Rawnsley Quartzite of South Australia. An analysis of over 5000 specimens demonstrates that fossil distribution is strongly controlled by facies and taphonomy rather than time or biogeography and that individual taxa vary considerably in their environmental tolerance and taphonomic integrity. The recognition that these taxa represent organisms living in various distinct environments, both juxtaposed and shared, holds strong implications for our interpretation of the record of early animal life on this planet and questions the biostratigraphic utility of the three associations. Furthermore, although in situ soft-bodied preservation provides a unique perspective on composition of benthic fossil assemblages, the record should not be interpreted as a simple "snapshot". Fossil beds represent a range of preservational modifi cations varying from current winnowed census samples of benthic communities at different depths and ecological maturity, to entirely transported assemblages. Unless the appropriate environments and taphonomic conditions are present for certain taxa, the absence of a particular taxon may or may not indicate its extinction in space or time.
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Interactions between organisms are a major determinant of the distribution and abundance of species. Ecology textbooks (e.g., Ricklefs 1984, Krebs 1985, Begon et al. 1990) summarise these important interactions as intra- and interspecific competition for abiotic and biotic resources, predation, parasitism and mutualism. Conspicuously lacking from the list of key processes in most text books is the role that many organisms play in the creation, modification and maintenance of habitats. These activities do not involve direct trophic interactions between species, but they are nevertheless important and common. The ecological literature is rich in examples of habitat modification by organisms, some of which have been extensively studied (e.g. Thayer 1979, Naiman et al. 1988).
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The sediments were all deposited in shallow or relatively shallow water, probably within tidal influence. The occurrence of some trace fossils normally only associated with deep water deposits suggests that these behavior patterns originated in shallow water in earliest Cambrian times and only later migrated into deep water. The diversity of trace fossils below the lowest trilobites in these and other sections suggests that they may have significant value in defining and correlating the Precambrian/Cambrian boundary.-from Authors
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The strange biota of Neoproterozoic sea bottoms become more understandable if we assume that otherwise soft sediments were sealed by firm and erosion-resistant biomats. This allowed 'mat encrusters' (vendobionts; trilobozoan and other sponges) to get attached to sandy bottoms, and molluscan 'mat scratchers' to scrape off an algal film, as if they were living on rocks. Minute conical 'mat stickers' (Cloudina) probably required a sticky substrate to become stabilized in upright position. Horizontal burrows are interpreted as the works of worm-like 'undermat miners.' Only the latter lifestyle appears to go back to the Mesoproterozoic; the others emerged in Vendian times and virtually disappeared when matgrounds became restricted to hostile environments in the wake of the Cambrian ecological revolution.
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Ediacaran and early Cambrian strata in NW Canada contain abundant trace fossils that record the progressive development of complex behavior in early animal evolution. Five feeding groups can be recognized: microbial grazing, deposit-feeding, deposit-feeding/predatory, filter-feeding/predatory, and arthropod tracks and trails. The lower Blueflower Formation (ca. 560-550 Ma) contains abundant burrows that completely cover bedding surfaces with small (similar to 1 mm diameter) cylindrical burrows that were strictly restricted to microbial bedding surfaces and exhibited only primitive and inconsistent avoidance strategies. The upper Blueflower contains three-dimensional avoidance burrows and rare filter-feeding or possibly predatory burrows, suggesting increased behavioral responses in food gathering that marked the beginning of the agronomic revolution in substrate utilization. Cambrian strata of the Ingta Formation contain systematically meandering burrows and more diverse feeding strategies, including the onset of treptichnid probing burrows that may reflect predation. These observations imply that Ediacaran burrowers were largely characterized by crude, two-dimensional avoidance meanders that represented simple behavioral responses of individual burrowers to sensory information, and that the subsequent development of more diverse and complex feeding patterns with genetically programmed search pathways occurred during the earliest stages of the Cambrian explosion. These observations further imply that changes occurred in both the food source and substrate during the ecological transition from Proterozoic matgrounds to Phanerozoic mixgrounds.
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The Avalon Assemblage (Ediacaran, late Neoproterozoic) provides some of the oldest evidence of diverse macroscopic life and underpins current understanding of the early evolution of epibenthic communities. However, its overall diversity and provincial variability are poorly constrained and are based largely on biotas preserved in Newfoundland, Canada. We report coeval high-diversity biotas from Charnwood Forest, UK, which share at least 60% of their genera in common with ones in Newfoundland. This indicates that substantial taxonomic exchange took place between different regions of Avalonia, probably facilitated by ocean currents, and suggests that a diverse deepwater biota may already have been widespread at the time. Contrasts in the relative abundance of prostrate versus erect taxa likely record differential sensitivity to physical environmental parameters (hydrodynamic regime, substrate) and highlight their significance in controlling community structure.
Article
Surface locomotory trace fossils from the Mistaken Point Formation of Newfoundland, dated at , 565 Ma, suggest that organisms capable of controlled locomotion and possessing muscular tissue may have existed among Avalonian Ediacaran macrofossil assemblages. Here we describe the Mistaken Point trace-fossil assemblage in full, discuss its stratigraphic context within the Mistaken Point Formation, and explore the competing hypotheses for the formation of the traces. We find that the trace fossils, preserved within a turbidite succession in a deep-marine depositional environment, are not attributable to abiogenic structures, to Ediacaran tubular or filamentous body fossils, to rangeomorph stems, or to a host of late Ediacaran and early Phanerozoic ichnofossils. Specimens within the assemblage show some similarities to the ichnogenera Helminthoidichnites and Archaeonassa, but discrepancies in certain aspects of their structure mean that we do not formally attribute them to these ichnotaxa at this time. The Mistaken Point ichnofossils possess morphological characteristics indicative of formation by an organism with a round base. Comparison with traces formed by modern organisms of such character appears to rule out formation by protistan, echinoderm, or annelid styles of movement, but is consistent with organisms moving via muscular controlled locomotion in a similar way to some modern mollusks and actinian cnidarians. We suggest therefore that the Mistaken Point trace-fossil assemblage reveals the presence of muscular metazoans in late Ediacaran deep-marine ecosystems. Such organisms cannot yet be attributed to specific phyla, but their inferred locomotory mechanisms share closest similarities with those utilized by extant actinians. INTRODUCTION
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REPLY Aspidella Evidence for Cnidaria-like behavior in ca. 560 Ma Ediacaran Email alerting services cite this article to receive free e-mail alerts when new articles www.gsapubs.org/cgi/alerts click Subscribe to subscribe to Geology www.gsapubs.org/subscriptions/ click Permission request to contact GSA http://www.geosociety.org/pubs/copyrt.htm#gsa click viewpoint. Opinions presented in this publication do not reflect official positions of the Society. positions by scientists worldwide, regardless of their race, citizenship, gender, religion, or political article's full citation. GSA provides this and other forums for the presentation of diverse opinions and articles on their own or their organization's Web site providing the posting includes a reference to the science. This file may not be posted to any Web site, but authors may post the abstracts only of their unlimited copies of items in GSA's journals for noncommercial use in classrooms to further education and to use a single figure, a single table, and/or a brief paragraph of text in subsequent works and to make GSA, employment. Individual scientists are hereby granted permission, without fees or further requests to Copyright not claimed on content prepared wholly by U.S. government employees within scope of their Notes © 2014 Geological Society of America on March 3, 2014 geology.gsapubs.org Downloaded from on March 3, 2014 geology.gsapubs.org Downloaded from
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A new assemblage of frondose and filamentous Ediacaran macrofossils is reported from the upper Drook Formation of Pigeon Cove, Newfoundland. The frondose forms, all less than 3 cm in length, are considered to represent the juvenile growth stages of Ediacaran organisms including Charnia spp. and Trepassia spp. This is the first report of an assemblage wholly dominated by such small juvenile rangeomorph forms, and provides insights into the ontogeny and ecology of these earliest members of the Ediacara biota. The fronds occur alongside filamentous forms with similarities to microbial taxa, and both morphotypes are considered to postdate an assemblage of large ivesheadiomorphs on the same bedding plane. If so, the assemblage represents one of the oldest documented examples of secondary community succession. The new Pigeon Cove fossils also extend the stratigraphic ranges of several key frondose taxa (Charnia masoni, Charniodiscus spp.) back into some of the oldest known macrofossil-bearing strata. These revised ranges lend support to the suggestion that the previously observed low diversity within the Drook Formation may represent a combination of taphonomic and sampling artefacts. Furthermore, this assemblage implies that the diversification of architectural morphotypes within the Ediacara biota took place earlier than hitherto suspected.
Article
Ediacaran strata in the Conception and St. John's groups that are exposed in the Catalina Dome, eastern Newfoundland, comprise a succession that is thinner but otherwise broadly similar to that known from the well-studied outcrops near Mistaken Point in southern Avalon Peninsula and Spaniard's Bay in northern Avalon. In all of these areas, strata consist of turbidites deposited in deep-water basin-plain and slope environments, but important differences help to constrain interpretations of basin history and Ediacaran paleobiology of eastern Newfoundland. A turbidite paleocurrent shift from easterly to southerly is consistent with the existing two-phase tectonic model for basin evolution previously proposed for the Avalon Peninsula. In the Catalina Dome, however, this shift occurred stratigraphically higher than at Mistaken Point but lower than at Spaniards Bay in the Avalon Peninsula. Probable seismoturbidites are common in the lower part of the Catalina succession, suggesting particularly active tectonism. Except in the very lowest 20 m of the succession (Drook and lowermost Mistaken Point formations) in which ash is absent, volcanic ash beds are both more common and more volumetrically significant throughout the succession than farther to the south and east, which suggests that deposition occurred closer to the volcanic arc. Volcanic ash beds persist higher stratigraphically, occurring within the Fermeuse Formation, which here contains diverse rangeomorph fossils in contrast with the low-diversity assemblage of Ediacaran discs prevalent in the Fermeuse Formation of the Avalon Peninsula. This distribution strongly reaffirms the importance of taphonomy in controlling the composition of deep-water Ediacaran assemblages.
Article
The Lantian biota at the Lantian Town of Xiuning County, Anhui Province, is preserved in black shales of the Ediacaran Lantian Formation. It yields some of the oldest known complex macroorganisms, including fan-shaped seaweeds and possible animal fossils with tentacles and intestinal-like structures reminiscent of modern coelenterates and bilaterians. The Lantian Lagerstätte sheds new light on the origin and early evolution of multicellular organisms in relatively quiet and deep environments soon after the Neoproterozoic Marinoan glaciation. The morphological complexity and diversity of early multicellular organisms may be closely related to sexual reproduction and alternation of generations. The fluctuation of oceanic redox conditions during this period may have played a role in the ecology and preservation of the Lantian biota.
Article
Distinguishing Ediacaran trace fossils from tubular body fossils can be a challenge, and several Ediacaran fossils previously interpreted as animal traces have been shown to be tubular body fossils. Nonetheless, true Ediacaran trace fossils are present, but they are relatively few and morphologically simple, dominated by horizontal trails and shallow burrows. Such simple morphologies have been taken as evidence for a modest behavioral complexity and limited geobiological impact of animal bioturbators before the Cambrian explosion. Here we report three types of trace fossils—horizontal tunnels, surface tracks/trails, and vertical traces—from the latest Ediacaran Dengying Formation (551–541 Ma) in the Yangtze Gorges area of South China. Cross-cutting tunnels and the presence of scratch marks indicate that these traces are unlikely tubular body fossils; instead, these three types of traces likely represent animal activities related to under-mat feeding, epibenthic locomotion, and temporary dwelling, respectively. We show that these three types of traces were constructed by the same bilaterian animals that had moderately complex interactions with microbial mats to exploit nutrients and O2 resources. These animals heralded a new age in ecosystem engineering, animal–sediment interaction, and biogeochemical cycling.
Article
Here we question the conclusions of Rogov et al. (2012), who claim to describe “the oldest evidence of bioturbation on Earth” in the form of meniscate backfi lled burrows and escape traces from late Ediacaran car- bonates of the Siberian Khatyspyt Formation. Because trace fossils can constrain early Metazoan origins, and are used to defi ne the base of the Cambrian Period (Brasier et al., 1994), such a signifi cant claim requires jus- tifi cation by careful interpretation of the material, and critical analysis, both of which appear wanting here. Although we agree that multiple biological and ecological revolutions took place during the late Ediacaran Period, we question whether those events can be tied to these problematic fossils.
Article
The transport of clay-size particles into the pore networks of siliciclastic sediments by the bioirrigating activities of burrowing organisms is demonstrated here for the first time. In a laboratory microcosm, evidence for the advection of kaolinite particles into pore spaces was observed at the interface between two buried sand layers. The clay transport was caused by the burrow-irrigating behavior of the mud shrimp Upogebia pugettensis. The term ''bioinfiltration'' is introduced herein to describe the process of particulate transport into pore-water networks. Given the abundance of bioirrigating organisms in shallow-marine environments, bioinfiltration may be a widespread phenomenon affecting the properties of large sediment volumes. The introduction of clay mineral particles into otherwise clay-free sediments through bioirrigation would affect the sediment characteristics significantly. In particular, bioinfiltrated clays would occlude pore space, could act as precursors to the production of authigenic cements, and inhibit the growth of quartz cements—all of which would reduce the permeability and porosity of hydrocarbon reservoirs and groundwater aquifers. Bioinfiltration therefore needs to be considered when assessing the origins and diagenetic effects of clay particles in bioturbated sediments, and is likely also to be of significance to sediment biogeochemistry and infaunal ecology. This is because of the potential influence of sedimentary pore occlusion on pore-water exchange, and through the introduction of particulate organic nutrients into the sediment as flocs or colloids. Such changes are likely to affect microbial productivity, which is thought to be the food source of many burrowing micro-and macro-organisms.
Article
Newly discovered fronds of the Ediacaran index fossil Charnia from the Drook Formation of southeastern Newfoundland are the oldest large, architecturally complex fossils known anywhere. Two species are present: Charnia masoni, originally described from Charnwood Forest in central England and now known worldwide, may have ranged through as much as 30 m.y. of Ediacaran time, and C. wardi sp. nov., a new species of Charnia that consists of slender fronds to nearly 2 m in length, is the longest Ediacaran fossil yet described anywhere. These fossils, which are present midway between the glacial diamictites of the Gaskiers Formation (ca. 595 Ma) and the classic Ediacaran assemblage of the Mistaken Point Formation (565 ± 3 Ma) 1500 m higher in the same section, provide our first glimpse of complex megascopic life after the meltdown of the ``snowball Earth'' glaciers.