Animal origins: The record from organic microfossils

Slater, Ben J.; Bohlin, Madeleine S.

doi:10.1016/j.earscirev.2022.104107

Cited by 17 publications

(11 citation statements)

References 204 publications

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“…In contrast, research on the biological affinity of acritarchs has rarely been a primary objective, and taxa that were not directly useful for biostratigraphy were often not studied in detail. Consequently, 'problematic' forms that are now receiving attention as SCFs have tended to be overlooked where they occur in standard palynological preparations (see also Slater and Bohlin 2022), with Goniomorpha being one of the few exceptions. With increasing interest in acritarchs and other organic-walled microfossils as repositories of palaeobiological information, in particular for understanding ancient biotas and the development of early ecosystems, acritarch research has now two additional tasks.…”

Section: Discussionmentioning

confidence: 99%

“…SCFs can be derived from a wide range of organisms, but many in the Cambrian assemblages represent sclerites and cuticular fragments of animals. There will inevitably be some overlap between SCFs and the smaller, more robust microfossils that dominate palynological preparations (discussed in Slater and Bohlin 2022). For example, certain spiny, conical microfossils observed in palynological preparations from the middle to upper Cambrian of Tennessee have been identified as the teeth of crustacean mandibles, via comparison with more extensive, articulated specimens recovered as SCFs from coeval rocks in western Canada (Harvey and Pedder 2013).…”

Section: Introductionmentioning

confidence: 99%

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Palynological recovery of small carbonaceous fossils (SCFs) indicates that the late Cambrian acritarch Goniomorpha Yin 1986 represents the teeth of a priapulid worm

et al. 2023

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New palynological studies from the Xiaoyangqiao section (Jilin Province, north-east China), which has been selected as an Auxiliary Boundary Stratigraphic Section and Point (ASSP) for the base of the Ordovician, confirms the presence of Goniomorpha Yin 1986 in intervals ranging from the late Cambrian (Furongian) to the Early Ordovician (Tremadocian), and allow us to clarify its morphology and affinities. Despite being compared originally to vesicular microfossils with processes arising from one pole, Goniomorpha lacks an enclosed cavity, so it cannot be classified as an acritarch in the strict sense. Instead, we find that the specimens originally described as Goniomorpha are actually part of a wider spectrum of morphologies that are identifiable as the pharyngeal teeth of priapulid worms. The best-preserved specimens resolve the 'processes' as denticles arising from an arch on the margins of a cuticular pad, sometimes with an extending spur and polygonal microstructure. Closely equivalent forms have been reported from Cambrian assemblages of small carbonaceous fossils (SCFs) and in situ on Burgess Shale specimens of the priapulid Ottoia. The findings from the Xiaoyangqiao section extend the taphonomic range of Cambrian-type SCFs into the Ordovician, and provide the first evidence for priapulids from the Ordovician of northern China. More generally, our results demonstrate the reciprocal insights from palynological and SCF-type processing for identifying problematic microfossils.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Palynological recovery of small carbonaceous fossils (SCFs) indicates that the late Cambrian acritarch Goniomorpha Yin 1986 represents the teeth of a priapulid worm

et al. 2023

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“…Butterfield et al 1994;Sergeev et al 2011;Tang et al 2017) and SCFs in the Cambrian (e.g. Harvey et al 2011;Butterfield and Harvey 2012;Slater et al 2017;Slater and Bohlin 2022). Many acritarchs are too small to be handpicked using a stereomicroscope, and a larger mesh size is used to sieve preparations for hand picking.…”

Section: Methodsmentioning

confidence: 99%

Organic-walled microfossils from the lower Cambrian of North Greenland: a reappraisal of diversity

Wallet,

Slater,

Willman

2023

Palynology

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The early Cambrian Buen Formation (North Greenland) hosts an exceptionally rich fossil biota that has contributed significantly to our knowledge of early metazoans, yet the fossil remains of primary producers from this deposit have received less attention. Here we examine the palynological component of the Buen Formation, with a focus on acritarchs and filamentous microfossils. Our analysis revealed the presence of 49 form taxa, 15 of which are described for the first time in the Buen Formation. These include large elements of presumably benthic origin, together with cyst-like acritarchs. Comasphaeridium longispinosum Vidal 1993 is renamed Comasphaeridium? brillesensis nom. nov., and Comasphaeridium densispinosum Vidal 1993 is reassigned to a new genus, Pearisphaeridium, becoming Pearisphaeridium densispinosum comb. nov. The diagnoses of Pearisphaeridium densispinosum (Vidal 1993) comb. nov. and Skiagia pura Moczydłowska 1988 are emended. Further, careful analysis of disparity in the recovered assemblage has revealed the presence of numerous transitional morphologies among the recorded acritarch form taxa. Though some of these transitional forms likely represent biologically meaningful entities (e.g. life cycle stages, ecophenotypes), others appear to have been artificially generated by taphonomic processes. Accounting for taphonomic factors and other sources of morphological variation has curtailed diversity down to 30 acritarch morphotypes, ten of which represent distinct abundance peaks broadly corresponding to acritarch genera. This analysis illustrates how population-based studies of early Cambrian acritarchs can help to discern the different factors that impinge on acritarch morphology, detect instances of taxonomic inflation, and refine our measures of diversity at the base of early Palaeozoic food webs.

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“…Despite their microscopic size and fragmentary nature, SCFs can preserve delicate non-biomineralized animal structures outside rare Lagerstätten sites [27][28][29][30][31]. Such SCFs offer a relatively under-exploited source of fossil mouthparts from early in animal evolution.…”

Section: Introductionmentioning

confidence: 99%

“…Such SCFs offer a relatively under-exploited source of fossil mouthparts from early in animal evolution. The emerging Cambrian SCF record has already yielded novel data on mouthparts and feeding apparatus that are otherwise invisible to the conventional fossil record [31]. For instance, exquisitely preserved mandibles captured among Cambrian SCF assemblages have extended the fossil record of particle-feeding crustaceans by approximately 100 Myr [30,[32][33][34][35].…”

Section: Introductionmentioning

confidence: 99%

Cambrian ‘sap-sucking’ molluscan radulae among small carbonaceous fossils (SCFs)

Slater

2023

Proc. R. Soc. B.

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Molluscs have produced an extensive fossil record, owing to the prevalence of robust biomineralized shells among this clade. By contrast, most other components of molluscan anatomy are seldom preserved. Importantly, little is known of the evolutionary history of the unique molluscan feeding apparatus—the radula. A scarcity of fossil radulae has hampered our understanding of the ancestral condition, and of the dietary ecology of early molluscs. The handful of known fossil radulae all point to early molluscs as simple deposit feeders that obtained food via rasping or scraping. This study reports microscopic radulae preserved as ‘small carbonaceous fossils' (SCFs) from Cambrian (Stage 4–Wuliuan, approximately 514–504.5 Ma) strata of Sweden. These rare fossil radulae offer novel insights into the feeding anatomy and ecology of early molluscs. Each radula comprises a uniseriate arc of (≤10) blade-shaped teeth, fringed by a slicing keel. This distinctive morphology is strikingly convergent with the radulae of extant sacoglossan heterobranch gastropods—such radulae are specially adapted for piercing the cell walls of green algal tissues to enable suctorial feeding on the cytoplasm contents. Discovery of analogous Cambrian radulae demonstrates this specialized form of herbivory had already evolved among molluscs more than half a billion years ago.

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Animal origins: The record from organic microfossils

Cited by 17 publications

References 204 publications

Palynological recovery of small carbonaceous fossils (SCFs) indicates that the late Cambrian acritarch Goniomorpha Yin 1986 represents the teeth of a priapulid worm

Palynological recovery of small carbonaceous fossils (SCFs) indicates that the late Cambrian acritarch Goniomorpha Yin 1986 represents the teeth of a priapulid worm

Organic-walled microfossils from the lower Cambrian of North Greenland: a reappraisal of diversity

Cambrian ‘sap-sucking’ molluscan radulae among small carbonaceous fossils (SCFs)

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