Intraspecific variation and taphonomic alteration in the Cambrian (Furongian) agnostoid Lotagnostus americanus: new information from China

Peng, Shanchi; Babcock, Loren E.; Zhu, Xuwei; Ahlberg, Per; Terfelt, Fredrik; Dai, Tao

doi:10.3140/bull.geosci.1500

Cited by 19 publications

(83 citation statements)

References 11 publications

(68 reference statements)

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“…Thus, this volcanic ash lies well above the base of Stage 10 with a base defined at the lowest occurrence of agnostoids termed Lotagnostus americanus in east Asia or Baltica (Peng et al, 2013(Peng et al, , 2015. Alternatively, this ash would lie just below a Stage 10 with its base defined at the lowest occurrence of Eoconodontus notchpeakensis (e.g., , see correlations in Westrop et al, 2011) (Fig.…”

Section: Figure 1 Terminal Cambrian and Earliest Ordovician Geochronomentioning

confidence: 96%

“…Subsequently, L. trisectus (Salter) was synonymized with L. americanus (Billings) by Peng and Babcock (2005). Thus, the lowest occurrence of a seemingly morphologically plastic agnostoid arthropod termed Lotagnostus americanus by some workers has been proposed for the base of Stage 10 (e.g., Peng and Babcock, 2005;Peng et al, 2013Peng et al, , 2015; compare…”

Section: Late Late Cambrian Datementioning

confidence: 99%

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Improved Geochronologic Accuracy and Precision for the ICS Chronostratigraphic Charts: Examples from the late Cambrian–Early Ordovician

et al. 2015

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The utility of ICS International Chronostratigraphic Charts (ICS Charts) relies on the accuracy and precision of reported geochronologic dates and their relationship to the bases of global chronostratigraphic units. However, an examination of some early Paleozoic dates (i.e., Cambrian-Ordovician boundary and lowest Ordovician) on the ICS Charts shows that they differ from originally reported and late recalculated dates. Thus, they record a numerical precision that differs from these revised dates. The dates assigned to the bases of formal early Paleozoic chronostratigraphic units may be interpreted by the lay reader as precise determinations, although they are almost all estimates based on dated horizons that stratigraphically bracket a chronostratigraphic unit's base. The bases of informal Cambrian chronostratigraphic units (e.g., Stage 10, ~489.5 Ma) are also assigned relatively precise ages although consensus does not exist on the horizon that should define an informal unit's base, and several alternative GSSP horizons with differing ages may exist. The uncertainties of the ICS Chart's dates on stage bases within the traditional Upper Cambrian are so great that the tilde (e.g., "~500.5") indicating "about" might be replaced by question marks or an abbreviation for "estimated." A preferred alternative is to replace the age estimates on the bases of informal and almost all formal chronostratigraphic divisions in the Phanerozoic with precise dates that bracket the bases of the divisions. The ICS Chart should include (perhaps on-line) brief discussions on and references to the history and procedures of age determination, accuracy, and precision for each dated horizon. An even more accurate, precise, and informative ICS Chart would result from review by a new ICS subcommission on geochronology. The subcommission could evaluate proposed dates for the ICS Chart for accuracy, precision, and suitability for determining/bracketing the ages of chronostratigraphic unit bases and provide updated reviews of the procedures used to determine all ICS Chart dates.

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Section: Figure 1 Terminal Cambrian and Earliest Ordovician Geochronomentioning

confidence: 96%

Section: Late Late Cambrian Datementioning

confidence: 99%

Improved Geochronologic Accuracy and Precision for the ICS Chronostratigraphic Charts: Examples from the late Cambrian–Early Ordovician

et al. 2015

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“…; Babcock & Peng ; Ergaliev & Ergaliev ; Dubinina ; Robison & Babcock ; Ahlberg & Terfelt ; Peng et al . ). Agnostoids are especially useful for correlation in open‐shelf and slope lithofacies, and for correlating intercontinentally, as they have been shown to have intercontinental to cosmopolitan distributions (e.g.…”

Section: Cambrian Biostratigraphymentioning

confidence: 97%

“…, ; Ergaliev & Ergaliev ; Ahlberg & Terfelt ; Peng et al . ; but see Westrop et al . for a contrasting view).…”

Section: Cambrian Biostratigraphymentioning

confidence: 99%

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Cambrian trilobite biostratigraphy and its role in developing an integrated history of the Earth system

Babcock

Shanchi

Ahlberg

2017

LET

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One of the principal biostratigraphical tools used in the lower Palaeozoic, and especially the Cambrian System, is trilobites. Historically, both polymerids and agnostoids have commonly been included as ‘trilobite’ groups, although currently the question of whether they comprise a monophyletic group or are polyphyletic is unsettled. Beginning in the late 1800s, the base of the Cambrian System was marked by the lowest occurrence of olenelline trilobites. Discovery of a rich pre‐trilobite metazoan record in the mid‐1900s led to significant modification of that concept, but polymerids and especially agnostoids still rank among the leading biostratigraphical and chronostratigraphical guides through much of the Cambrian. Chronostratigraphical sub‐division of the trilobite‐bearing part of the Cambrian System derives largely from biostratigraphical, ecological and evolutionary concepts about agnostoids and polymerids introduced in the 1940s to 1970s by A.H. Westergård, A.R. Palmer and R.A. Robison. Westergård introduced a zonation for Scandinavia that was largely based on agnostoids. Palmer explained the distribution of Cambrian trilobite faunas in terms of restricted and unrestricted access to open oceans. Together, these ideas coalesced in Robison's recognition of separate zonation schemes for restricted‐shelf polymerids, open‐shelf polymerids and open‐shelf (cosmopolitan) agnostoids. Palmer also introduced the concept of biomeres, which placed sharp limits on biostratigraphical intervals recognizable from trilobites. Global correlation in the upper half of the Cambrian today depends to a large extent on the ranges of agnostoids and some polymerids characteristic of open‐shelf to slope areas, ones that facilitate identification of precise intercontinental tie points. Agnostoid and polymerid biostratigraphy is now being integrated with information about coastal onlap and eustatic sea‐level history, geochemical cycling and other data to provide a more complete understanding of the early Palaeozoic biosphere and its complex physico‐chemical context.

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Cambrian integrative stratigraphy and timescale of China

Zhu

Yang

Jingliang

et al. 2018

Sci. China Earth Sci.

166

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Intraspecific variation and taphonomic alteration in the Cambrian (Furongian) agnostoid Lotagnostus americanus: new information from China

Cited by 19 publications

References 11 publications

Improved Geochronologic Accuracy and Precision for the ICS Chronostratigraphic Charts: Examples from the late Cambrian–Early Ordovician

Improved Geochronologic Accuracy and Precision for the ICS Chronostratigraphic Charts: Examples from the late Cambrian–Early Ordovician

Cambrian trilobite biostratigraphy and its role in developing an integrated history of the Earth system

Cambrian integrative stratigraphy and timescale of China

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