Chancelloriid sclerites from the lowermost Cambrian of North China and discussion of sclerite taxonomy

Yun, Hao; Zhang, Xingliang; Li, Luoyang; Pan, Bing; Li, Guoxiang; Brock, Glenn A.

doi:10.1016/j.geobios.2019.02.001

Cited by 11 publications

(16 citation statements)

References 26 publications

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“…2011; Yun et al . 2019b) documenting the presence of similar sclerites in scleritomes dominated by sclerites with central rays. While sclerites from the genus Allonnia can be superficially similar to these, their rays are generally set at a much higher angle relative to the basal plane (see Moore et al .…”

Section: Resultsmentioning

confidence: 99%

“…4 is considered 4 + 0 rather than 3 + 1) ; but note the different convention of Yun et al . (2019b).…”

Section: Methodsmentioning

confidence: 99%

“…2002; Bengtson & Collins 2015) and seemingly monospecific assemblages of isolated sclerites (Sdzuy 1969; Yun et al . 2019b) suggests that distributions of the number of rays within a sclerite from a single scleritome are generally continuous and unimodal. More qualitatively (as discussed further below under Systematic Palaeontology) sclerites from a single species are generally relatively similar to one another (in the curvature and taper of their rays, in the symmetry of the sclerite, in the orientation of marginal rays relative to the basal plane, in their ornamentation, etc.…”

Section: Methodsmentioning

confidence: 99%

“…1990) and an assemblage from the Xinji Formation of North China attributed to C. eros by Yun et al . (2019b). Obliquely (rather than vertically) oriented articulatory facets surrounding the central ray are elsewhere documented from C. ‘ hispanica ’ (Sdzuy, 1969, non Richter & Richter, 1940) and C. lilioides (see below).…”

Section: Systematic Palaeontologymentioning

confidence: 99%

“…2019; Yun et al . 2019b). It seems reasonable to think, therefore, that even if single isolated sclerites may not always be identifiable, biologically meaningful species can be determined from studies of large assemblages of isolated sclerites.…”

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confidence: 99%

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Chancelloriid sclerites from the Dyeran–Delamaran (‘Lower–Middle’ Cambrian) boundary interval of the Pioche–Caliente region, Nevada,USA

Moore

Porter

Webster

et al. 2019

Papers in Palaeontology

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Chancelloriids are a poorly understood group of phylogenetically problematic Cambrian metazoans; complete specimens show they were sessile, radially symmetrical, club‐shaped organisms covered with sclerites in the form of rosettes of spines. While isolated sclerites are common components of Cambrian shelly assemblages, they have been relatively little studied. We describe chancelloriid sclerites from a series of nine sections spanning the upper Dyeran to lower Delamaran stages (latest Stage 4 to perhaps basal Wuliuan) from the Pioche–Caliente region of east‐central Nevada, USA. Acid maceration of samples from the Combined Metals, Comet Shale and Susan Duster Limestone members of the Pioche Formation yielded more than 2000 sclerites. Based on careful examination of these sclerites and statistical analyses of co‐occurring sclerite types, we distinguish six species, each with a restricted stratigraphic range. Chancelloria impar Moore sp. nov. is the dominant species in most upper Dyeran samples. Archiasterella cometensis Moore sp. nov. and A. auriculata Moore sp. nov. are rare in the upper Dyeran but abundant in the lowest Delamaran; A. uncinata Moore sp. nov. and C. lilioides Moore sp. nov. replace these in younger samples. A. auriculata is noteworthy for sharing features with species of both Archiasterella and Chancelloria. These results provide further support for the taxonomic tractability and biostratigraphical utility of chancelloriid sclerites; large collections from single horizons allow intraspecific variability to be assessed and species to be distinguished. Our results document a taxonomic turnover in chancelloriids at the Dyeran–Delamaran boundary, showing that not only trilobites were affected at this time.

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Section: Resultsmentioning

confidence: 99%

“…4 is considered 4 + 0 rather than 3 + 1) ; but note the different convention of Yun et al . (2019b).…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Systematic Palaeontologymentioning

confidence: 99%

mentioning

confidence: 99%

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Chancelloriid sclerites from the Dyeran–Delamaran (‘Lower–Middle’ Cambrian) boundary interval of the Pioche–Caliente region, Nevada,USA

Moore

Porter

Webster

et al. 2019

Papers in Palaeontology

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Small shelly fossils and carbon isotopes from the early Cambrian (Stages 3–4) Mural Formation of western Laurentia

Skovsted

Balthasar

Vinther

et al. 2020

Papers in Palaeontology

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The extraordinary window of phosphatized and phosphatic small shelly fossils (SSF) during the early and middle Cambrian is an important testament to the radiation of biomineralizing metazoans. While SSF are well known from most Cambrian palaeocontinents during this time interval, western Laurentia has relatively few SSF faunas.Here we describe a diverse SSF fauna from the early Cambrian (Stages 3-4) Mural Formation at three localities in Alberta and British Columbia, Canada, complemented by carbon isotope measurements to aid in a potential future bio-chemostratigraphic framework. The fauna expands the recorded SSF assemblage diversity in western Laurentia and includes several brachiopods, four bradoriids, three chancelloriids, two hyoliths, a tommotiid and a helcionellid mollusc as well as echinoderm ossicles and specimens of Microdictyon, Volborthella and Hyolithellus. New taxa include the tommotiid genus Canadiella gen. nov., the new bradoriid species Hipponicharion perforata sp. nov. and Pseudobeyrichona taurata sp. nov. Compared with contemporaneous faunas from western Laurentia, the fauna is relatively diverse, particularly in taxa with originally phosphatic shells, which appear to be associated with archaeocyathid build-ups. This suggests that the generally low faunal diversity in western Laurentia may be at least partly a consequence of poor sampling of suitable archaeocyathan reef environments. In addition, the tommotiid Canadiella filigrana appears to be of biostratigraphical significance in Cambrian Stage 3 strata of western Laurentia, and the unexpected high diversity of bradoriid arthropods in the fauna also suggests that this group may prove useful for biostratigraphical resolution in the region.

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Body reconstruction, taxonomy, and biostratigraphy of a ‘problematic’ chancelloriid

Yun¹,

Reitner²,

Zhang³

2023

PalZ

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Chancelloriids are a group of ‘problematic’ fossils characterized by bag-shaped body equipped with mineralized sclerites on the external surface. Among the chancelloriid taxa, the genus Dimidia was known only by isolated sclerites from small shelly faunas and once regarded as a junior synonym of Allonnia. The complete body of Dimidia simplex Jiang is described herein for the first time, based on well-preserved specimens from the Chengjiang biota (Cambrian Stage 3) of South China. The name Dimidia is resurrected since the characteristic sclerites in the scleritome are distinctive within all known chancelloriid genera with complete bodies. The sclerites of Dimidia are densely arranged, each composed of two symmetrical, acute rays that pointed out with their long axes nearly vertical to the body surface, structurally representing an intermediate type between the single-rayed and the common rosette-like composite sclerites of chancelloriids. The remains of Dimidia were previously found across South China, Gondwana, and Laurentia, and stratigraphically ranging from the upper Stage 2 to Wuliuan Stage of the Cambrian. The discovery of complete bodies of Dimidia contributes to revealing the diversity and clarifying the ‘problematic’ taxonomy of chancelloriids, and emphasizes the necessity to scrutinize more scleritome fossils to interpret the taxonomy and phylogenetic affinity of other small shelly fossils.

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Chancelloriid sclerites from the lowermost Cambrian of North China and discussion of sclerite taxonomy

Cited by 11 publications

References 26 publications

Chancelloriid sclerites from the Dyeran–Delamaran (‘Lower–Middle’ Cambrian) boundary interval of the Pioche–Caliente region, Nevada,USA

Chancelloriid sclerites from the Dyeran–Delamaran (‘Lower–Middle’ Cambrian) boundary interval of the Pioche–Caliente region, Nevada,USA

Small shelly fossils and carbon isotopes from the early Cambrian (Stages 3–4) Mural Formation of western Laurentia

Body reconstruction, taxonomy, and biostratigraphy of a ‘problematic’ chancelloriid

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