The oldest evidence of bioturbation on Earth: COMMENT

Brasier, Martin D.; McIlroy, Duncan; Liu, Alexander; Antcliffe, Jonathan B.; Menon, Latha R.

doi:10.1130/g33606c.1

Cited by 28 publications

(16 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Mángano & Buatois, ). The only well‐documented possible example of extensive latest Ediacaran sediment mixing has been reported from the Khatyspyt Formation of Siberia (Rogov et al , ), but remains under discussion as an alternative interpretation of body fossils must be considered (Brasier et al , ; Gámez Vintaned & Zhuravlev, ; Rogov et al , 2013 a , b ). Overall we think it is important to repeat our conviction (Budd & Jensen, , ) that the radical difference between typical Ediacaran and Cambrian trace fossils, both in size and complexity (see Fig.…”

Section: The Fate Of the Ediacarans And The Rise Of The Bilateriansmentioning

confidence: 99%

The origin of the animals and a ‘Savannah’ hypothesis for early bilaterian evolution

2015

View full text Add to dashboard Cite

The earliest evolution of the animals remains a taxing biological problem, as all extant clades are highly derived and the fossil record is not usually considered to be helpful. The rise of the bilaterian animals recorded in the fossil record, commonly known as the 'Cambrian explosion', is one of the most significant moments in evolutionary history, and was an event that transformed first marine and then terrestrial environments. We review the phylogeny of early animals and other opisthokonts, and the affinities of the earliest large complex fossils, the so-called 'Ediacaran' taxa. We conclude, based on a variety of lines of evidence, that their affinities most likely lie in various stem groups to large metazoan groupings; a new grouping, the Apoikozoa, is erected to encompass Metazoa and Choanoflagellata. The earliest reasonable fossil evidence for total-group bilaterians comes from undisputed complex trace fossils that are younger than about 560 Ma, and these diversify greatly as the Ediacaran-Cambrian boundary is crossed a few million years later. It is generally considered that as the bilaterians diversified after this time, their burrowing behaviour destroyed the cyanobacterial mat-dominated substrates that the enigmatic Ediacaran taxa were associated with, the so-called 'Cambrian substrate revolution', leading to the loss of almost all Ediacara-aspect diversity in the Cambrian. Why, though, did the energetically expensive and functionally complex burrowing mode of life so typical of later bilaterians arise? Here we propose a much more positive relationship between late-Ediacaran ecologies and the rise of the bilaterians, with the largely static Ediacaran taxa acting as points of concentration of organic matter both above and below the sediment surface. The breaking of the uniformity of organic carbon availability would have signalled a decisive shift away from the essentially static and monotonous earlier Ediacaran world into the dynamic and burrowing world of the Cambrian. The Ediacaran biota thus played an enabling role in bilaterian evolution similar to that proposed for the Savannah environment for human evolution and bipedality. Rather than being obliterated by the rise of the bilaterians, the subtle remnants of Ediacara-style taxa within the Cambrian suggest that they remained significant components of Phanerozoic communities, even though at some point their enabling role for bilaterian evolution was presumably taken over by bilaterians or other metazoans. Bilaterian evolution was thus an essentially benthic event that only later impacted the planktonic environment and the style of organic export to the sea floor.

show abstract

Section: The Fate Of the Ediacarans And The Rise Of The Bilateriansmentioning

confidence: 99%

The origin of the animals and a ‘Savannah’ hypothesis for early bilaterian evolution

2015

View full text Add to dashboard Cite

show abstract

“…As early as 565 Ma, apparent burrow‐like structures associated with a “meniscate” lining have been proposed as the first evidence for bioturbation (Rogov et al., ). The biogenic nature of these specimens has been questioned (Brasier, McIlroy, Liu, Antcliffe, & Menon, ), but alternative trace fossils are indicative of some form of movement through sediment during roughly the same time period (Liu, McIlroy, & Brasier, ). There is evidence for shallow burrows from about 560 Ma (Menon, McIlroy, & Brasier, ), followed by an observable increase in burrow size, and their appearance in more shoreward environments from about 540 Ma (Droser & Bottjer, ; McIlroy & Logan, ).…”

Section: Introductionmentioning

confidence: 99%

Bioturbation and directionality in Earth's carbon isotope record across the Neoproterozoic–Cambrian transition

et al. 2018

View full text Add to dashboard Cite

Mixing of sediments by moving animals becomes apparent in the trace fossil record from about 550 million years ago (Ma), loosely overlapping with the tail end of the extreme carbonate carbon isotope δ C fluctuations that qualitatively distinguish the Proterozoic geochemical record from that of the Phanerozoic. These Precambrian-scale fluctuations in δ C (PSF-δ C ) remain enigmatic, due to their high amplitude and inclusion of global-scale negative δ C values, below anything attributable to mantle input. Here, we note that different biogeochemical-model scenarios plausibly explaining globally synchronous PSF-δ C converge: via mechanistic requirements for extensive anoxia in marine sediments to support sedimentary build-up of C-depleted carbon. We hypothesize that bioturbation qualitatively reduced marine sediment anoxia by exposing sediments to oxygenated overlying waters, which ultimately contributed to decreasing the carbon cycle's subsequent susceptibility to PSF- δ C . Bioturbation may also have reduced the quantity of (isotopically light) organic-derived carbon available to contribute to PSF- δ C via ocean crust carbonatization at depth. We conduct a comparative modelling exercise in which we introduce bioturbation to existing model scenarios for PSF- δ C : expressing both the anoxic proportion of marine sediments, and the global organic carbon burial efficiency, as a decreasing function of bioturbation. We find that bioturbation's oxygenating impact on sediments has the capacity to prevent PSF- δ C caused by authigenic carbonate precipitation or methanogenesis. Bioturbation's impact on the f-ratio via remineralization is partially offset by liberation of organic phosphate, some of which feeds back into new production. We emphasize that this study is semiquantitative, exploratory and intended merely to provide a qualitative theoretical framework within which bioturbation's impact on long-term, first-order δ C can be assessed (and it is hoped quantified in more detail by future work). With this proviso, we conclude that it is entirely plausible that bioturbation made a decisive contribution to the enigmatic directionality in the δ C record, from the Neoproterozoic-Cambrian boundary onwards.

show abstract

“…In contrast to fossil lagerstätten, the trace-fossil record is continuous through the critical Ediacaran -Cambrian interval. Higher BIs have been indicated recently for the Ediacaran [23], but the illustrated structures consist of serially repeated elements, identical to those in problematic body fossils such as Helanoichnus, Palaeopascichnus and Shaanxilithes [24], arguing against a trace-fossil origin [25]. Trace fossils documented in the Avalon assemblage (565 Ma) [21] have not been attributed to bilaterians and therefore they have not included in the diagram.…”

Section: (C) Cambrian Stagementioning

confidence: 99%

Decoupling of body-plan diversification and ecological structuring during the Ediacaran–Cambrian transition: evolutionary and geobiological feedbacks

2014

View full text Add to dashboard Cite

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.

show abstract

The oldest evidence of bioturbation on Earth: COMMENT

Cited by 28 publications

References 9 publications

The origin of the animals and a ‘Savannah’ hypothesis for early bilaterian evolution

The origin of the animals and a ‘Savannah’ hypothesis for early bilaterian evolution

Bioturbation and directionality in Earth's carbon isotope record across the Neoproterozoic–Cambrian transition

Decoupling of body-plan diversification and ecological structuring during the Ediacaran–Cambrian transition: evolutionary and geobiological feedbacks

Contact Info

Product

Resources

About