Diverse biomineralizing animals in the terminal Ediacaran Period herald the Cambrian explosion

Cai, Yao; Xiao, Shuhai; Li, Guoxiang; Hong, Hui

doi:10.1130/g45949.1

Cited by 81 publications

(44 citation statements)

References 38 publications

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“…These fossils ultimately suggest the divergence of at least the basal-most annelid branches (the palaeoannelids and chaetopterids) within the Cambrian Period 60 . We thus advocate an expanded investigation of the diversity of unresolved but comparable tubiform fossils across the Ediacaran-Cambrian transition 13 in an effort to help potentially connect these records.…”

Section: Resultsmentioning

confidence: 99%

“…Nonetheless, the most crucial task that remains is to untangle the potential relationships between the organisms of the Ediacaran Period and those well-defined as metazoans in the Cambrian Period. The cloudinomorphs are one of the few groups known to span the Ediacaran-Cambrian boundary 13 , and thus understanding their phylogenetic position is key to unraveling the evolutionary and ecological relationships between the seemingly disparate biomes of the Ediacaran and Cambrian Periods.…”

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confidence: 99%

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Discovery of bilaterian-type through-guts in cloudinomorphs from the terminal Ediacaran Period

et al. 2020

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The fossil record of the terminal Ediacaran Period is typified by the iconic index fossil Cloudina and its relatives. These tube-dwellers are presumed to be primitive metazoans, but resolving their phylogenetic identity has remained a point of contention. The root of the problem is a lack of diagnostic features; that is, phylogenetic interpretations have largely centered on the only available source of information-their external tubes. Here, using tomographic analyses of fossils from the Wood Canyon Formation (Nevada, USA), we report evidence of recognizable soft tissues within their external tubes. Although alternative interpretations are plausible, these internal cylindrical structures may be most appropriately interpreted as digestive tracts, which would be, to date, the earliest-known occurrence of such features in the fossil record. If this interpretation is correct, their nature as one-way through-guts not only provides evidence for establishing these fossils as definitive bilaterians but also has implications for the long-debated phylogenetic position of the broader cloudinomorphs.

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Section: Resultsmentioning

confidence: 99%

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Discovery of bilaterian-type through-guts in cloudinomorphs from the terminal Ediacaran Period

et al. 2020

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“…Anabaritids have their origin in the terminal Ediacaran (Cai et al, 2019), and are one of the most abundant components of the earliest small shelly faunas. These triradially symmetrical tubes made up of growth lamellae consisting of bundles of fibres ( Fig.…”

Section: The Evidence For the Early Evolution Of Animal Skeletonsmentioning

confidence: 99%

The ‘biomineralization toolkit’ and the origin of animal skeletons

Murdock

2020

Biological Reviews

112

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Biomineralized skeletons are widespread in animals, and their origins can be traced to the latest Ediacaran or early Cambrian fossil record, in virtually all animal groups. The origin of animal skeletons is inextricably linked with the diversification of animal body plans and the dramatic changes in ecology and geosphere–biosphere interactions across the Ediacaran–Cambrian transition. This apparent independent acquisition of skeletons across diverse animal clades has been proposed to have been driven by co‐option of a conserved ancestral genetic toolkit in different lineages at the same time. This ‘biomineralization toolkit’ hypothesis makes predictions of the early evolution of the skeleton, predictions tested herein through a critical review of the evidence from both the fossil record and development of skeletons in extant organisms. Furthermore, the distribution of skeletons is here plotted against a time‐calibrated animal phylogeny, and the nature of the deep ancestors of biomineralizing animals interpolated using ancestral state reconstruction. All these lines of evidence point towards multiple instances of the evolution of biomineralization through the co‐option of an inherited organic skeleton and genetic toolkit followed by the stepwise acquisition of more complex skeletal tissues under tighter biological control. This not only supports the ‘biomineralization toolkit’ hypothesis but also provides a model for describing the evolution of complex biological systems across the Ediacaran–Cambrian transition.

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“…In this regard, the terminal Ediacaran Dengying Formation at the Gaojiashan section (referred to as the DYF@GJS hereafter) can offer key insights (see details in Section 2). Although the bio-and chemostratigraphy of the DYF@GJS has been previously studied (Meyer et al 2012;Cai et al 2014Cai et al , 2019Cui et al 2016b), no complete and integrated chemostratigraphic profiles have ever been published for the entire DYF@GJS.…”

Section: Introductionmentioning

confidence: 99%

Sedimentology and chemostratigraphy of the terminal Ediacaran Dengying Formation at the Gaojiashan section, South China

et al. 2019

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The terminal Ediacaran Dengying Formation (c. 551.1–538.8 Ma) in South China is one of two successions where Ediacara-type macrofossils are preserved in carbonate facies along with skeletal fossils and bilaterian animal traces. Given the remarkable thickness of carbonate-bearing strata deposited in less than 12.3 million years, the Dengying Formation holds the potential for construction of a relatively continuous chemostratigraphic profile for the terminal Ediacaran Period. In this study, a detailed sedimentological and chemostratigraphic (δ13Ccarb, δ18Ocarb, δ13Corg, δ34Spyrite, and 87Sr/86Sr) investigation was conducted on the Dengying Formation at the Gaojiashan section, Ningqiang County of southern Shaanxi Province, South China. Sedimentological results reveal an overall shallow-marine depositional environment. Carbonate breccia, void-filling botryoidal precipitates and aragonite crystal fans are common in the Algal Dolomite Member of the Dengying Formation, suggesting that peritidal facies were repeatedly karstified. The timing of karstification was likely early, probably soon after the deposition of the dolomite sediments. The presence of authigenic aragonite cements suggests high alkalinity in the terminal Ediacaran ocean. Geochemical analysis of micro-drilled samples shows that distinct compositions are registered in different carbonate phases, which should be considered when constructing chemostratigraphic profiles representative of true temporal variations in seawater chemistry. Integrated chemostratigraphic data suggest enhanced burial of organic carbon and pyrite, and the occurrence of extensive marine anoxia (at least in the Gaojiashan Member). Rapid basinal subsidence and carbonate accumulation during a time of elevated seawater alkalinity and increased rates of pyrite burial may have facilitated the evolutionary innovation of early biomineralizing metazoans.

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Diverse biomineralizing animals in the terminal Ediacaran Period herald the Cambrian explosion

Cited by 81 publications

References 38 publications

Discovery of bilaterian-type through-guts in cloudinomorphs from the terminal Ediacaran Period

Discovery of bilaterian-type through-guts in cloudinomorphs from the terminal Ediacaran Period

The ‘biomineralization toolkit’ and the origin of animal skeletons

Sedimentology and chemostratigraphy of the terminal Ediacaran Dengying Formation at the Gaojiashan section, South China

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