Protracted development of bioturbation through the early Palaeozoic Era

Tarhan, Lidya G.; Droser, Mary L.; Planavsky, Noah J.; Johnston, David T.

doi:10.1038/ngeo2537

Cited by 121 publications

(152 citation statements)

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“…Focusing on shared conditions, the second explanation ascribes the decline in exceptional preservation in the upper Neoproterozoic-lower Paleozoic to secular changes in near-surface marine environments (Allison and Briggs, 1993), which broadly affected all taphonomic processes and lastingly restricted soft tissue conservation in marine settings. Overall, the trend broadly follows the prolonged oxygenation of the ocean-atmosphere system (Gill et al, 2011; and the protracted development of the sediment mixed layer (Tarhan et al, 2015), the zone of sediment homogenized and fluidized via bioturbation by burrowing animals, in the early Paleozoic. These changes in marine environments affected exceptional preservation by promoting scavenging of buried carcasses (Allison and Briggs, 1993); enhancing the seawater concentrations of O 2 and SO 4 2 − used in the main microbial metabolisms of decay (Canfield and Farquhar, 2009;Tarhan et al, 2015); deepening the sedimentary aerobic and sulfate reduction zones in which soft tissues are most aggressively degraded Schiffbauer et al, 2014b); and reducing the prevalence of microbial mats, which facilitate authigenic/diagenetic mineralization by sealing fossils off from oxic or suboxic bottom waters (Gehling, 1999;Laflamme et al, 2011) and preventing efflux of precipitating geochemical species (Callow and Brasier, 2009;.…”

Section: Exceptional Preservation Through Time In Marine Settingsmentioning

confidence: 99%

Exceptionally Preserved Fossil Assemblages Through Geologic Time and Space

Muscente¹,

Laflamme²,

Schiffbauer³

et al. 2016

Geological Society of America Abstracts With Programs

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Geologic deposits containing fossils with remains of non-biomineralized tissues (i.e. Konservat-Lagerstätten) provide key insights into ancient organisms and ecosystems. Such deposits are not evenly distributed through geologic time or space, suggesting that global phenomena play a key role in exceptional fossil preservation. Nonetheless, establishing the influence of global phenomena requires documenting temporal and spatial trends in occurrences of exceptionally preserved fossil assemblages. To this end, we compiled and analyzed a dataset of 694 globally distributed exceptional fossil assemblages spanning the history of complex eukaryotic life (~610 to 3 Ma). Our analyses demonstrate that assemblages with similar ages and depositional settings commonly occur in clusters, each signifying an ancient geographic region (up to hundreds of kilometers in scale), which repeatedly developed conditions conducive to soft tissue preservation. Using a novel hierarchical clustering approach, we show that these clusters decrease in number and shift from open marine to transitional and nonmarine settings across the Cambrian-Ordovician interval. Conditions conducive to exceptional preservation declined worldwide during the early Paleozoic in response to transformations of near-surface environments that promoted degradation of tissues and curbed authigenic mineralization potential. We propose a holistic explanation relating these environmental transitions to ocean oxygenation and bioturbation, which affected virtually all taphonomic pathways, in addition to changes in seawater chemistry that disproportionately affected processes of soft tissue conservation. After these transitions, exceptional preservation rarely occurred in open marine settings, excepting times of widespread oceanic anoxia, when low oxygen levels set the stage. With these patterns, nonmarine cluster count is correlated with non-marine rock quantity, and generally decreases with age. This result suggests that geologic processes, which progressively destroy terrestrial rocks over time, limit sampling of non-marine deposits on a global scale. Future efforts should aim to assess the impacts of such phenomena on evolutionary and ecological patterns in the fossil record.

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Section: Exceptional Preservation Through Time In Marine Settingsmentioning

confidence: 99%

Exceptionally Preserved Fossil Assemblages Through Geologic Time and Space

Muscente¹,

Laflamme²,

Schiffbauer³

et al. 2016

Geological Society of America Abstracts With Programs

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“…Extant meioendobenthic organisms are particularly important contributors to biogeochemical cycling, microbial ecology and ecosystem productivity, especially in muddy sediments 27,37 . Multiple studies discuss the trace fossil record of macrofaunal behaviour from the late Ediacaran onwards, its postulated impacts on sediment geochemistry and benthic ecology, and its role in ecosystem engineering and ecological escalation 1,2,8 . Constraining the deep time origins of a meiofaunal mode of life may be equally important for understanding the biological and chemical evolution of marine sedimentary environments.…”

Section: Nature Ecology and Evolutionmentioning

confidence: 99%

“…Our understanding of early animal evolution is complemented by ichnological investigations of latest Ediacaran to Ordovician strata 1,2,8 . Diverse ichnofossil assemblages in the earliest Cambrian place an important constraint on the tempo of bilaterian origins, as they indicate that some groups, including total group panarthropods and priapulid-like scalidophorans 2,9 , were globally distributed and abundant by this point.…”

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confidence: 99%

Ichnological evidence for meiofaunal bilaterians from the terminal Ediacaran and earliest Cambrian of Brazil

et al. 2017

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The evolutionary events during the Ediacaran-Cambrian transition (~541 Myr ago) are unparalleled in Earth history. The fossil record suggests that most extant animal phyla appeared in a geologically brief interval, with the oldest unequivocal bilaterian body fossils found in the Early Cambrian. Molecular clocks and biomarkers provide independent estimates for the timing of animal origins, and both suggest a cryptic Neoproterozoic history for Metazoa that extends considerably beyond the Cambrian fossil record. We report an assemblage of ichnofossils from Ediacaran-Cambrian siltstones in Brazil, alongside U-Pb radioisotopic dates that constrain the age of the oldest specimens to 555-542 Myr. X-ray microtomography reveals three-dimensionally preserved traces ranging from 50 to 600 μ m in diameter, indicative of small-bodied, meiofaunal tracemakers. Burrow morphologies suggest they were created by a nematoid-like organism that used undulating locomotion to move through the sediment. This assemblage demonstrates animal-sediment interactions in the latest Ediacaran period, and provides the oldest known fossil evidence for meiofaunal bilaterians. Our discovery highlights meiofaunal ichnofossils as a hitherto unexplored window for tracking animal evolution in deep time, and reveals that both meiofaunal and macrofaunal bilaterians began to explore infaunal niches during the late Ediacaran. NATuRE ECoLoGy & EvoLuTIoN Articles Nature ecology & evolutioNsupport for these suggestions is limited to purported body fossils of sponges 19 and demosponge biomarkers 20 . A considerable gap therefore remains between the fossil record of the late Ediacaran and molecular clock estimates for deep splits in the animal tree, for example the origin of Metazoa and Eumetazoa 3 . Assuming that contemporary molecular clock analyses yield accurate, if imprecise 18 , node ages for animal divergences, a small body size and concomitant limited fossilization potential 21 could reconcile these discordant records of animal evolution (but see ref. 22 ).The small body size of the ancestral bilaterian is supported by recent phylogenomic analyses of deep animal relationships, with acoel flatworms and xenoturbellids (Xenacoelomorpha) being a sister group to all remaining bilaterians (Nephrozoa) 23 , and smallbodied spiralian taxa (the 'Platyzoa') recognized as a paraphyletic grade with respect to macroscopic trochozoans 24 . This suggests that early bilaterians and spiralians were small bodied, possibly meiofaunal, and moved using ciliary gliding.Meiofauna comprises all organisms between 32 and 1,000 μ m in size that inhabit pore-water-rich sediments in freshwater to deepmarine environments 25 . Modern meiofaunal communities include animals, foraminifera and some ciliates, and contribute significantly to sediment bioturbation and bioirrigation 26,27 . The meiofauna can be divided into permanent members (that is, animals with organisms of a small size adapted and restricted to the meiofaunal, interstitial realm) and temporary meiofauna (for example, the ...

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“…A method that provides quantitative measures for bioturbation and sediment mixing during this critical interval could have important applications. Bioturbation intensity (BI) has generally two components (horizontal and vertical), which show different aspects of infaunal behavior; the vertical component is usually the one used to analyze advances or innovation in trace making (Droser et al, 2005bSeilacher, 2007;Tarhan et al, 2015). Here we propose an adjusted BI for 3D data, the Volumetric Bioturbation Intensity (VBI).…”

Section: Estimating Bioturbation Intensity: 3d Vs 2dmentioning

confidence: 99%

“…Animal trace fossils from the Ediacaran Period (635-541 Ma) are often particularly difficult to examine due to their small size, their simplicity, and their tendency to be preserved on a single plane of preservation (Droser et al, 2005a;Jensen et al, 2005;Sappenfield et al, 2011). Additionally, simple animal traces from the Ediacaran Period are sometimes similar to tubular body fossils and their preservation in microbial substrates renders it difficult to distinguish Ediacaran body and trace fossils based on bedding plane observation alone (Droser et al, 1999(Droser et al, , 2002Jensen et al, 2006;Sappenfield et al, 2011;Tarhan et al, 2015Tarhan et al, , 2013. Lamonte trevallis is a relatively large Ediacaran ichnospecies that is preserved differently than most trace fossils from the time period.…”

Section: Introductionmentioning

confidence: 99%

Beyond the stony veil: Reconstructing the Earth’s earliest large animal traces via computed tomography X-ray imaging

Meyer

Polys

Yaqoob

et al. 2017

Precambrian Research

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a b s t r a c tTrace fossils are superb lines of evidence for examining the ancient biologic world because they offer an opportunity to infer behavioral ecology of organisms. However, traces can be difficult to parse from their matrix, which leads to the loss of important morphological and behavioral data. This is especially true for the earliest marine animal traces from the Ediacaran Period (635-541 Ma), which are usually small (<5 mm in diameter) and simple (mostly small horizontal trails and burrows), and are sometimes difficult to be distinguished from co-existing tubular body fossils. There is also evidence that the prevalence of microbial substrates in Ediacaran oceans may have influenced emerging trace makers in nonactualistic ways from a late Phanerozoic perspective (e.g., microbial mats may have facilitated a strong geochemical gradient across the sediment-water interface). Therefore, the discovery of the relatively large traces of Lamonte trevallis from the Ediacaran Shibantan Member of the Denying Formation ($551-541 Ma) in the Yangtze Gorges area of South China provides a unique opportunity to study early bioturbators. These trace fossils are large enough and have sufficient compositional contrast (relative to the matrix) for in situ analysis via X-ray computed tomography (CT) and microcomputed tomography (microCT). Each analytical method has its own advantages and disadvantages. CT scans can image larger specimens, but cannot adequately resolve small features of interest. MicroCT scans can achieve higher resolution, but can only be used with small samples and may involve more post-processing than CT scans. As demonstrated in this study, X-ray CT and microCT in combination with other 3D imaging techniques and resources have the potential to resolve the 3D morphology of Ediacaran trace fossils. A new Volumetric Bioturbation Intensity (VBI) is also proposed, which quantifies whole rock bioturbation using 3D analysis of subsurface traces. Combined with the ability to examine trace fossils in situ, the VBI can enhance our view of ancient ecologies and life's enduring relationship with sediments.

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Protracted development of bioturbation through the early Palaeozoic Era

Cited by 121 publications

References 34 publications

Exceptionally Preserved Fossil Assemblages Through Geologic Time and Space

Exceptionally Preserved Fossil Assemblages Through Geologic Time and Space

Ichnological evidence for meiofaunal bilaterians from the terminal Ediacaran and earliest Cambrian of Brazil

Beyond the stony veil: Reconstructing the Earth’s earliest large animal traces via computed tomography X-ray imaging

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