Lower Cambrian helcionelloid molluscs from Estonia

Isakar, Mare; Peel, John S.

doi:10.1080/11035890701293255

Cited by 9 publications

(7 citation statements)

References 20 publications

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“…This pattern is considered to reflect the torsion of the animal, and thus Pelagiella is generally regarded as a primitive, torted (at least partly) gastropod. The radial ridges or channels along the circumbilical shoulder of the moulds in Pelagiella (Isakar & Peel 2007), Xinjispira and Protowenella (herein) are interpreted to be formed during ontogeny by spirally migrating muscle scars. These muscle scars are more or less comparable to the columellar muscles of modern gastropods (Price 2003).…”

Section: Discussionmentioning

confidence: 95%

Revisiting the molluscan fauna from the Cambrian (Series 2, stages 3–4) Xinji Formation of North China

Zhang

Skovsted

et al. 2019

Papers in Palaeontology

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A diverse group of molluscs from the Cambrian Series 2, Stages 3–4 Xinji Formation of the North China Block (NCB) is described, based on more than 4500 specimens from three well‐studied sections in Shaanxi and Henan provinces, along the southern and southwestern margin of the NCB. Twenty molluscan species are identified, including one bivalve, three stem group gastropods, and 16 additional helcionelloids. Among these, six helcionelloid species are reported from the NCB for the first time, and one new species, Parailsanella luonanensis sp. nov. is proposed. This diverse molluscan fauna shares a large number of species with contemporaneous faunas of South Australia (15), Antarctica (7), Laurentia (6), Siberia (3) and South China (1). Faunal similarities are even greater on a generic level. The striking similarities of the molluscan faunas of North China, South Australia and Antarctica strongly support the hypothesis that the NCB was situated close to Eastern Gondwana, most likely close to South Australia in the Cambrian Epoch 2. In addition, well‐preserved shell attachment muscle scars were observed in the helcionelloid Figurina figurina, with two pairs of symmetrical, continuous, band‐like muscle scars, which are obviously different from the musculature of both gastropods and monoplacophorans. Because of this unique musculature, these characteristic Cambrian cap‐like molluscs are assigned to the Helcionelloida rather than to the Gastropoda or Monoplacophora.

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Section: Discussionmentioning

confidence: 95%

Revisiting the molluscan fauna from the Cambrian (Series 2, stages 3–4) Xinji Formation of North China

Zhang

Skovsted

et al. 2019

Papers in Palaeontology

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“…This better resolved placement in the mollusks is unlikely to resolve its taxonomic position. The genus has, for example, been considered a member of the helcionellaceans, within the monoplacophora (Runnegar and Jell, 1976) and as a helcionelloid (Peel, 1991a; see Isakar and Peel, 2007, p. 255–256 for a review of the taxonomic history of Scenella as a mollusk). Due to the low number of specimens described here and the uncertainty surrounding the taxonomy of Scenella , an attempt to rectify its higher taxonomic relationships shall not be made.…”

Section: Systematic Paleontologymentioning

confidence: 99%

Mollusks from the upper Shackleton Limestone (Cambrian Series 2), Central Transantarctic Mountains, East Antarctica

et al. 2019

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An assemblage of Cambrian Series 2, Stages 3–4, conchiferan mollusks from the Shackleton Limestone, Transantarctic Mountains, East Antarctica, is formally described and illustrated. The fauna includes one bivalve, one macromollusk, and 10 micromollusks, including the first description of the speciesXinjispira simplexZhou and Xiao, 1984 outside North China. The new fauna shows some similarity to previously described micromollusks from lower Cambrian glacial erratics from the Antarctic Peninsula. The fauna, mainly composed of steinkerns, is relatively low diversity, but the presence of diagnostic taxa, including helcionelloidDavidonia rostrata(Zhou and Xiao, 1984), bivalvePojetaia runnegariJell, 1980, cambroclavidCambroclavus absonusConway Morris in Bengtson et al., 1990, and bradoriidSpinospitella coronataSkovsted et al., 2006, as well as the botsfordiid brachiopodSchizopholis yorkensis(Ushatinskaya and Holmer in Gravestock et al., 2001), in the overlying Holyoake Formation correlates the succession to theDailyatia odysseiZone (Cambrian Stages 3–4) in South Australia.

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“…The Sämi Member is overlain by the green‐grey to red‐brown silt‐rich claystones of the Mahu Member. The succeeding Kestla Member is predominantly claystone, but has numerous thin fine sand and silt beds, and hosts a low‐diversity SSF assemblage including the helcionelloid molluscs Aldanella kunda and Anabarella plana (Isakar & Peel ). The uppermost Tammaneeme Member is restricted to the western region of the Estonian Lontova Formation, and consists of coarser dark grey siltstones (Mens & Pirrus ; Kirsimäe et al .…”

Section: Geological Settingmentioning

confidence: 99%

“…Sediments of the Lontova and Voosi formations lack trilobites, so biostratigraphical schemes have relied on SSFs, acritarchs and trace fossils. The SSF Aldanella kunda occurs in the uppermost parts of the Lontova Formation in Estonia and is widely considered to be a junior synonym of A. attleborensis (Landing ; Isakar & Peel ; Parkhaev & Karlova ). A. attleborensis has previously been suggested as a potential Stage 2 index fossil (e.g.…”

Section: Geological Settingmentioning

confidence: 99%

Small carbonaceous fossils (SCFs) from the Terreneuvian (lower Cambrian) of Baltica

2018

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We describe a new assemblage of small carbonaceous fossils (SCFs) from diagenetically minimally altered clays and siltstones of Terreneuvian age from the Lontova and Voosi formations of Estonia, Lithuania and Russia. This is the first detailed account of an SCF assemblage from the Terreneuvian and includes a number of previously undocumented Cambrian organisms. Recognizably bilaterian-derived SCFs include abundant protoconodonts (total-group Chaetognatha), and distinctive cuticular spines of scalidophoran worms. Alongside these metazoan remains are a range of protistan-grade fossils, including Retiranus balticus gen. et sp. nov., a distinctive funnel-shaped or sheet-like problematicum characterized by terminal or marginal vesicles, and Lontohystrichosphaera grandis gen. et sp. nov., a large (100-550 lm) ornamented vesicular microfossil.Together these data offer a fundamentally enriched view of Terreneuvian life in the epicratonic seas of Baltica, from an episode where records of non-biomineralized life are currently sparse. Even so, the recovered assemblages contain a lower diversity of metazoans than SCF biotas from younger (Stage 4) Baltic successions that represent broadly equivalent environments, echoing the diversification signal recorded in the coeval shelly and trace-fossil records. Close comparison to the biostratigraphical signal from Fortunian small shelly fossils supports a late Fortunian age for most of the Lontova/Voosi succession, rather than a younger (wholly Stage 2) range.

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Lower Cambrian helcionelloid molluscs from Estonia

Cited by 9 publications

References 20 publications

Revisiting the molluscan fauna from the Cambrian (Series 2, stages 3–4) Xinji Formation of North China

Revisiting the molluscan fauna from the Cambrian (Series 2, stages 3–4) Xinji Formation of North China

Mollusks from the upper Shackleton Limestone (Cambrian Series 2), Central Transantarctic Mountains, East Antarctica

Small carbonaceous fossils (SCFs) from the Terreneuvian (lower Cambrian) of Baltica

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