Ordovician calcified cyanobacteria and associated microfossils from the Tarim Basin, Northwest China: systematics and significance

Liu, Lijing; Wu, Yasheng; Yang, Haijun; Riding, Robert

doi:10.1080/14772019.2015.1030128

Cited by 32 publications

(63 citation statements)

References 63 publications

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“…A cyanobacterial affinity was proposed for Rothpletzella by a few authors (Wood, 1948;Wray, 1977;Nose et al, 2006). Yet recently Rothpletzella is regarded as a microproblematicum, since no extant analogs are known (Riding, 1977b(Riding, , 1991Liu et al, 2016). The diameters of Rothpletzella tubes (25-40 µm) observed in this study fall into the diameter range described for filamentous cyanobacteria (e.g., Scytonema, Phormidium or Plectonema).…”

Section: Rothpletzellamentioning

confidence: 61%

“…The former possibility is in agreement with previous interpretations that Rothpletzella might be a colony-forming cyanobacterium. Its morphology and wall structure are similar to those of Plectonema, which in turn is considered as a probable extant analog of Girvanella (Riding, 1977a;Liu et al, 2016).…”

Section: Rothpletzellamentioning

confidence: 99%

“…As in the case with Allonema, the taxonomical classification of Rothpletzella is unclear. Although a cyanobacterial affinity is proposed by a few authors (Jarochowska and Munnecke, 2014), Rothpletzella is often regarded as incertae sedis (Riding, 1991;Liu et al, 2016).…”

Section: Rothpletzellamentioning

confidence: 99%

“…Branching dichotomously in one plane is very common (Flügel, 2004). Rothpletzella commonly cooccurs with Allonema (Liu et al, 2016;Zhang et al, 2017). Both are common in Palaeozoic back-reef, fore-reef, as well as openmarine and semi-restricted shelf limestones, where they play an important role in the formation of oncoids and mounds of microbial origin (e.g., Shen and Neuweiler, 2016).…”

Section: Rothpletzellamentioning

confidence: 99%

“…The phylogenetic position of Allonema is controversial and underwent many revisions since it was tentatively established by Ulrich and Bassler (1904), who classified it as a ctenostome bryozoan. Most recent publications regard Allonema as incertae sedis (Jarochowska and Munnecke, 2014;Wilson and Taylor, 2014;Liu et al, 2016).…”

Section: Calcareous Microproblematicamentioning

confidence: 99%

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Distinguishing Biologically Controlled Calcareous Biomineralization in Fossil Organisms Using Electron Backscatter Diffraction (EBSD)

et al. 2018

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Although carbonate-precipitating cyanobacteria are ubiquitous in aquatic ecosystems today, the criteria used to identify them in the geological record are subjective and rarely testable. Differences in the mode of biomineralization between cyanobacteria and eukaryotes, i.e., biologically induced calcification (BIM) vs. biologically controlled calcification (BCM), result in different crystallographic structures which might be used as a criterion to test cyanobacterial affinities. Cyanobacteria are often used as a "wastebasket taxon," to which various microfossils are assigned. The lack of a testable criterion for the identification of cyanobacteria may bias their fossil record severely. We employed electron backscatter diffraction (EBSD) to investigate the structure of calcareous skeletons in two microproblematica widespread in Palaeozoic marine ecosystems: Rothpletzella, hypothesized to be a cyanobacterium, and an incertae sedis microorganism Allonema. We used a calcareous trilobite shell as a BCM reference. The mineralized structure of Allonema has a simple single-layered structure of acicular crystals perpendicular to the surface of the organism. The c-axes of these crystals are parallel to the elongation and thereby normal to the surface of the organism. EBSD pole figures and misorientation axes distribution reveal a fiber texture around the c-axis with a small degree of variation (up to 30 • ), indicating a highly ordered structure. A comparable pattern was found in the trilobite shell. This structure allows excluding biologically induced mineralization as the mechanism of shell formation in Allonema. In Rothpletzella, the c-axes of the microcrystalline sheath show a broader clustering compared to Allonema, but still reveal crystals tending to be perpendicular to the surface of the organism. The misorientation axes of adjacent crystals show an approximately random distribution. Rothpletzella also shares morphological similarities with extant cyanobacteria. We propose that the occurrence of a strong misorientation relationship between adjacent crystals with misorientation axes clustering around the c-axis can be used as a proxy for the degree of control exerted by an organism on its mineralized structures. Therefore, precisely constrained distributions of misorientations (misorientation angle and misorientation axis) may be used to identify BCM in otherwise problematic fossils and can be used to ground-truth the cyanobacterial affinities commonly proposed for problematic extinct organisms.

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Section: Rothpletzellamentioning

confidence: 61%

Section: Rothpletzellamentioning

confidence: 99%

Section: Rothpletzellamentioning

confidence: 99%

Section: Rothpletzellamentioning

confidence: 99%

Section: Calcareous Microproblematicamentioning

confidence: 99%

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Distinguishing Biologically Controlled Calcareous Biomineralization in Fossil Organisms Using Electron Backscatter Diffraction (EBSD)

et al. 2018

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Xianella: a new mat‐forming calcified cyanobacterium from the Middle–Late Ordovician of North China

Lee

Riding

2016

Papers in Palaeontology

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Xianella hongii gen. et sp. nov. is described from the Middle–Late Ordovician of Shaanxi, China and interpreted as a calcified cyanobacterial sheath. Xianella filaments formed cable‐like strands that constructed thick fenestral layers. The specimens occur in metre‐sized limestone blocks, possibly derived from local collapse of a reefal platform margin. In combination with micrite, some of which is intraclastic and peloidal, Xianella created thick and extensive stacks of layered calcified fenestral fabric that appear to be synsedimentarily calcified open‐frame mat deposits. The fenestrae range from small, laminose and very irregular, to large equidimensional areas ~2 cm across. Fenestrae with rounded outlines resemble primary gas bubbles observed in present‐day microbial mats. These delicate fabrics are comparable in structure and quality of preservation with those of some Proterozoic silicified stromatolitic mats.

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Calcilobes wangshenghaii n. gen., n. sp., microbial constructor of Permian–Triassic boundary microbialites of South China, and its place in microbialite classification

Kershaw

Zhang

2021

Facies

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Permian–Triassic boundary microbialites (PTBMs) that formed directly after the end-Permian extinction in the South China Block are dominated by one structure, a lobate-form calcium carbonate construction that created extensive very thin (ca. 2–20 m thick) framework biostromes in shallow marine environments, effectively occupying the ecological position of the prior pre-extinction Permian reefs and/or associated carbonates. In the field, vertical sections show the microbialite is dendrolite (branched) and thrombolite (clotted), but because thrombolite may include branched portions, its structure is overall best classed as thrombolite. In the field and in polished blocks, the microbial material appears as dark carbonate embedded in lighter-coloured micritic sediment, where details cannot be seen at that scale. In thin section, in contrast to the largely unaltered micritic matrix, the microbial constructor is preferentially partly to completely recrystallised, but commonly passes gradationally over distances of a few mm to better-preserved areas comprising 0.1–0.2 mm diameter uneven blobs of fine-grained calcium carbonate (micrite to microsparite). The lobate architecture comprises branches, layers and clusters of blobs ca. 1–20 mm in size, and includes constructed cavities with geopetal sediments, cements and some deposited small shelly fossils. Individual blobs in the matrix may be fortuitous tangential cross sections through margins of accumulated masses, but if separate, may represent building blocks of the masses. The lobate structure is recognised here as a unique microbial taxon and named Calcilobes wangshenghaii n. gen., n. sp. Calcilobes reflects its calcium carbonate composition and lobate form, wangshenghaii for the Chinese geologist (Shenghai Wang) who first detailed this facies in 1994. The structure is interpreted as organically built, and may have begun as separate blobs on the sea floor sediment (that was also composed of micrite but is interpreted as mostly inorganic), by microbial agglutination of micrite. Because of its interpreted original micritic–microsparitic nature, classification as either a calcimicrobe (calcified microbial fossil) or a sedimentary microbial structure is problematic, so C. wangshenghaii has uncertain affinity and nature. Calcilobes superficially resembles Renalcis and Tarthinia, which both form small clusters in shallow marine limestones and have similar problems of classification. Nevertheless, Calcilobes framework architecture contrasts both the open branched geometry of Renalcis, and the small tighter masses of Tarthinia, yet it is more similar to Tarthinia than to Renalcis, and may be a modification of Tarthinia, noting that Tarthinia is known from only the Cambrian. Calcilobes thus joins Renalcis, Tarthinia and also Epiphyton (dendritic form) and others, as problematic microbial structures. Calcilobes has not been recognised elsewhere in the geological record and may be unique to the post-end-Permian extinction facies. C. wangshenghaii occurs almost exclusively in the South China Block, which lay on the eastern margin of Tethys Ocean during Permian–Triassic boundary times; reasons for its absence in western Tethys, except for comparable fabrics in one site in Iran and another in Turkey, are unknown.

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Ordovician calcified cyanobacteria and associated microfossils from the Tarim Basin, Northwest China: systematics and significance

Cited by 32 publications

References 63 publications

Distinguishing Biologically Controlled Calcareous Biomineralization in Fossil Organisms Using Electron Backscatter Diffraction (EBSD)

Distinguishing Biologically Controlled Calcareous Biomineralization in Fossil Organisms Using Electron Backscatter Diffraction (EBSD)

Xianella: a new mat‐forming calcified cyanobacterium from the Middle–Late Ordovician of North China

Calcilobes wangshenghaii n. gen., n. sp., microbial constructor of Permian–Triassic boundary microbialites of South China, and its place in microbialite classification

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