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Journal Article

Cambrian trilobites from the Nounan Dolomite and lower St. Charles Formation (upper Marjuman to lower Sunwaptan; Miaolingian to Furongian Series), Smithfield Canyon, northern Utah Open Access

Frederick A. Sundberg, Hannah R. Cothren, Carol M. Dehler
Published: 01 July 2024
Journal of Paleontology (2024) 98 (4): 537–566.
DOI: https://doi.org/10.1017/jpa.2023.48
.... Trilobite materials collected for this study occur in the Nounan and St. Charles formations and range from the Cedaria to Ellipsocephaloides biozones. These biozones represent the upper Marjuman, Steptoean, and lower Sunwaptan stages of Laurentia and the international upper Guzhangian, Paibian...
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View PDF for article title, Cambrian trilobites from the Nounan Dolomite and lower St. Charles Formation (upper Marjuman to lower <span class="search-highlight">Sunwaptan</span>; Miaolingian to Furongian Series), Smithfield Canyon, northern Utah
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Journal Article

Faunal and paleoenvironmental changes at a Cambrian (Jiangshanian; Steptoean–Sunwaptan boundary interval) trilobite extinction event, in contrasting deep- and shallow-subtidal settings, Nevada and Oklahoma Open Access

Stephen R. Westrop, Katie F. Welch, Michael H. Engel, Jonathan M. Adrain
Published: 01 July 2024
Journal of Paleontology (2024) 98 (4): 584–611.
DOI: https://doi.org/10.1017/jpa.2023.75
...Stephen R. Westrop; Katie F. Welch; Michael H. Engel; Jonathan M. Adrain Abstract Successions in Oklahoma and Nevada record trilobite extinction and replacement near the Steptoean–Sunwaptan boundary in inner-shelf and outer-shelf settings, respectively. Prior to the extinctions, different trilobite...
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View PDF for article title, Faunal and paleoenvironmental changes at a Cambrian (Jiangshanian; Steptoean–<span class="search-highlight">Sunwaptan</span> boundary interval) trilobite extinction event, in contrasting deep- and shallow-subtidal settings, Nevada and Oklahoma
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Journal Article

A new Cambrian (Jiangshanian, Sunwaptan) trilobite fauna from Oklahoma and its biostratigraphic significance. Open Access

Sean R. Blackwell, Stephen R. Westrop
Published: 01 July 2023
Journal of Paleontology (2023) 97 (4): 865–890.
DOI: https://doi.org/10.1017/jpa.2023.40
...Sean R. Blackwell; Stephen R. Westrop Abstract The Cambrian (Jiangshanian, Sunwaptan) Honey Creek Formation in the Wichita Mountains region of Oklahoma yielded a new fauna dominated by Monocheilus Resser, 1937 (senior synonym of Stigmacephalus Resser, 1937 ) in association with Ptychaspis Hall...
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View PDF for article title, A new Cambrian (Jiangshanian, <span class="search-highlight">Sunwaptan</span>) trilobite fauna from Oklahoma and its biostratigraphic significance.
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Journal Article

Linguliform brachiopods across a Cambrian–Ordovician (Furongian, Early Ordovician) biomere boundary: the Sunwaptan–Skullrockian North American Stage boundary in the Wilberns and Tanyard formations of central Texas Available to Purchase

Rebecca L. Freeman, James F. Miller, Benjamin F. Dattilo
Published: 30 May 2018
Journal of Paleontology (2018) 92 (5): 751–767.
DOI: https://doi.org/10.1017/jpa.2018.8
... of trilobite ‘biomeres’ that correspond to North American stages, including those of the Sunwaptan and Skullrockian. Trilobites show a consistent pattern of recovery across these boundaries, and commonly each extinction and replacement of taxa is interpreted as a single event as changing environmental...
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View PDF for article title, Linguliform brachiopods across a Cambrian–Ordovician (Furongian, Early Ordovician) biomere boundary: the <span class="search-highlight">Sunwaptan</span>–Skullrockian North American Stage boundary in the Wilberns and Tanyard formations of central Texas
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Journal Article

Biogeographic Shifts in a Transgressive Succession: The Cambrian (Furongian, Jiangshanian; Latest Steptoean–Earliest Sunwaptan) Agnostoid Arthropods Kormagnostella Romanenko and Biciragnostus Ergaliev in North America Available to Purchase

Stephen R. Westrop, Jonathan M. Adrain
Published: 01 September 2013
Journal of Paleontology (2013) 87 (5): 804–817.
DOI: https://doi.org/10.1666/12-111
... interval in the Steptoean–Sunwaptan boundary interval (Furongian, Jiangshanian) of Nevada and Utah. In Nevada, both genera occur in a condensed bioclastic lag below a major flooding surface, and Kormagnostella also appears in a transgressive interval in Utah. Immigration of these genera is associated...
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View PDF for article title, Biogeographic Shifts in a Transgressive Succession: The Cambrian (Furongian, Jiangshanian; Latest Steptoean–Earliest <span class="search-highlight">Sunwaptan</span>) Agnostoid Arthropods Kormagnostella Romanenko and Biciragnostus Ergaliev in North America
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Add to Citation Manager for Biogeographic Shifts in a Transgressive Succession: The Cambrian (Furongian, Jiangshanian; Latest Steptoean–Earliest <span class="search-highlight">Sunwaptan</span>) Agnostoid Arthropods Kormagnostella Romanenko and Biciragnostus Ergaliev in North America
Journal Article

Bartonaspis new genus, a trilobite species complex from the base of the Upper Cambrian Sunwaptan Stage in North America Available to Purchase

Stephen R. Westrop, Jonathan M. Adrain
Published: 30 August 2007
Canadian Journal of Earth Sciences (2007) 44 (7): 987–1003.
DOI: https://doi.org/10.1139/e07-009
...Stephen R. Westrop; Jonathan M. Adrain Abstract Despite being reported widely from basal Sunwaptan strata, Dellea? punctata Palmer, 1965 , is known from only four figured cranidia. New material from Nevada, Utah and Oklahoma, including librigenae and pygidia, indicate that specimens assigned...
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View PDF for article title, Bartonaspis new genus, a trilobite species complex from the base of the Upper Cambrian <span class="search-highlight">Sunwaptan</span> Stage in North America
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Journal Article

NOTCHPEAKIA , A NEW GENUS OF UPPER CAMBRIAN (SUNWAPTAN) “ENTOMASPIDID” TRILOBITES Available to Purchase

JONATHAN M. ADRAIN, STEPHEN R. WESTROP
Published: 01 November 2006
Journal of Paleontology (2006) 80 (6): 1152–1171.
DOI: https://doi.org/10.1666/0022-3360(2006)80[1152:NANGOU]2.0.CO;2
...JONATHAN M. ADRAIN; STEPHEN R. WESTROP Abstract Trilobites previously assigned to the Entomaspididae Ulrich in Bridge, 1931 are common in Laurentian strata assigned to the upper Sunwaptan Stage of the Upper Cambrian. Most species are poorly known, and typically only sparse cranidial data...
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View PDF for article title, NOTCHPEAKIA , A NEW GENUS OF UPPER CAMBRIAN (<span class="search-highlight">SUNWAPTAN</span>) “ENTOMASPIDID” TRILOBITES
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Journal Article

A NEW SUNWAPTAN (LATE CAMBRIAN) TRILOBITE FAUNA FROM THE UPPER MISSISSIPPI VALLEY Available to Purchase

STEPHEN R. WESTROP, ALLISON R. PALMER, ANTHONY RUNKEL
Published: 01 January 2005
Journal of Paleontology (2005) 79 (1): 72–88.
DOI: https://doi.org/10.1666/0022-3360(2005)079<0072:ANSLCT>2.0.CO;2
...STEPHEN R. WESTROP; ALLISON R. PALMER; ANTHONY RUNKEL Abstract A single bed at the base of the Jordan Sandstone in a road cut at Arcadia, Wisconsin, yielded an undescribed Late Sunwaptan ( Saukia Zone) trilobite fauna that includes at least four species from the families Dikelocephalidae Miller...
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View PDF for article title, A NEW <span class="search-highlight">SUNWAPTAN</span> (LATE CAMBRIAN) TRILOBITE FAUNA FROM THE UPPER MISSISSIPPI VALLEY
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Figure 7. Stage-level pattern of evenness and biodiversity in the Cambrian and Ordovician. Lines connecting the Steptoean and Sunwaptan and the Sunwaptan and Arenigian stages are dashed to indicate the unconstrained nature of the Sunwaptan data. Gray points are individual samples; mean sample value ± one standard error of the mean shown for each stage. Essmin, evenness measure (Appendix); J, Pielou's evenness measure; PIE, Hurlburt's probability of interspecific encounter; H Shannon-Wiener diversity index. Timescale abbreviations: De, Delamaran; Mj, Marjuman; St, Steptoean; Su, Sunwaptan; Are, Arenigian; Car, Caradocian; Ash, Ashgillian

Figure 7. Stage-level pattern of evenness and biodiversity in the Cambrian... Available to Purchase

Published: 01 January 2004
Figure 7. Stage-level pattern of evenness and biodiversity in the Cambrian and Ordovician. Lines connecting the Steptoean and Sunwaptan and the Sunwaptan and Arenigian stages are dashed to indicate the unconstrained nature of the Sunwaptan data. Gray points are individual samples; mean sample
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Figure 8. Evenness pattern in whole assemblages including non-benthic taxa (top) and for samples pooled on the basis of stratigraphic formation (bottom). Gray points are individual samples; mean sample value ± one standard error of the mean is shown for each stage. Lines connecting the Steptoean and Sunwaptan and the Sunwaptan and Arenigian stages are dashed to indicate the unconstrained nature of the Sunwaptan data (see text). Timescale abbreviations as in Figure 7

Figure 8. Evenness pattern in whole assemblages including non-benthic taxa... Available to Purchase

Published: 01 January 2004
and Sunwaptan and the Sunwaptan and Arenigian stages are dashed to indicate the unconstrained nature of the Sunwaptan data (see text). Timescale abbreviations as in Figure 7
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Distribution of trilobite genera, trilobite shell beds and orthid brachiopod shell beds in extinction intervals at the bases of the Sunwaptan and Skullrockian stages at Wilcox Peak, Alberta (data from Westrop, 1984). (1) Lower Sunwaptan strata of the Bison Creek Formation. (2) Lower Skullrockian strata of the basal silty member, Survey Peak Formation.

Distribution of trilobite genera, trilobite shell beds and orthid brachiopo... Open Access

Published: 01 July 2024
Figure 15. Distribution of trilobite genera, trilobite shell beds and orthid brachiopod shell beds in extinction intervals at the bases of the Sunwaptan and Skullrockian stages at Wilcox Peak, Alberta (data from Westrop, 1984 ). ( 1 ) Lower Sunwaptan strata of the Bison Creek Formation. ( 2
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Pseudagnostus josepha (Hall, 1863) from the Sunwaptan Stage, St. Charles Formation, Smithfield Canyon, Utah. All specimens are from USNM loc. 44304. (1–3) Exfoliated cephalon USNM 775702: (1) dorsal view; (2) lateral view; (3) anterior view. (4) Partially testate cephalon USNM 775706. (5) Mostly testate cephalon USNM 775705. (6–8) Mostly testate pygidium USNM 775700: (6) dorsal view; (7) lateral view; (8) anterior view. (9) Exfoliated cephalon USNM 775703. (10) Testate pygidium USNM775704. (11) Mostly testate pygidium USNM 775707. (12) Mostly exfoliated pygidium USNM 775699. (13) Exfoliated pygidium USNM 775701.

Pseudagnostus josepha (Hall, 1863 ) from the Sunwaptan Stage, St. Charles... Open Access

Published: 01 July 2024
Figure 5. Pseudagnostus josepha (Hall, 1863 ) from the Sunwaptan Stage, St. Charles Formation, Smithfield Canyon, Utah. All specimens are from USNM loc. 44304. ( 1–3 ) Exfoliated cephalon USNM 775702: ( 1 ) dorsal view; ( 2 ) lateral view; ( 3 ) anterior view. ( 4 ) Partially testate cephalon
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Trilobites from the Sunwaptan Stage, St. Charles Formation, Smithfield Canyon, Utah. All specimens are from USNM loc. 44304, exfoliated or mostly exfoliated. (1–10) Saratogia (Idahoia) aff. S. (I.) fria Lochman and Hu, 1959: (1) small partial cranidium USNM 781838; (2) cranidium USNM 781837; (3) exfoliated cranidium USNM 781826; (4) cranidia USNM 781824 and 781825 (upper right); (5) partial cranidium USNM 781836; (6) silicified librigena USNM 781827; (7) cranidium USNM 781835; (8) cranidium USNM 781833; (9) exfoliated partial cranidium USNM 781839; (10) silicified librigena USNM 781828. (11–16) Wilbernia cf. W. explanata (Whitfield, 1880): (11) partial cranidium USNM 781832; (12, 13) cranidium USNM 781829: (12) dorsal view; (13) anterior view; (14) mostly exfoliated librigena USNM 781834; (15) testate pygidium USNM 781831; (16) partial pygidium USNM 781830. (1) White scale bar = 2 mm; (2–16) specimens use the 4 mm scale bar.

Trilobites from the Sunwaptan Stage, St. Charles Formation, Smithfield Cany... Open Access

Published: 01 July 2024
Figure 19. Trilobites from the Sunwaptan Stage, St. Charles Formation, Smithfield Canyon, Utah. All specimens are from USNM loc. 44304, exfoliated or mostly exfoliated. ( 1–10 ) Saratogia ( Idahoia ) aff. S. ( I. ) fria Lochman and Hu, 1959 : ( 1 ) small partial cranidium USNM 781838; ( 2
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Wilbernia species from the Sunwaptan Stage, St. Charles Formation, Smithfield Canyon, Utah. All specimens are from USNM loc. 44303. (1–3) Wilbernia aff. W. pero (Whitfield, 1880), partial, exfoliated cranidium USNM 781843: (1) dorsal view; (2) lateral view; (3) anterior view. (4–11) Wilbernia aff. W. expansa Frederickson, 1949: (4–6) mostly testate cranidium USNM 781841: (4) dorsal view; (5) anterior view; (6) lateral view; (7) exfoliated librigena USNM 781840; (8–11) mostly testate pygidium USNM 781842: (8) inverted counterpart dorsal showing ornamentation; (9) dorsal view; (10) lateral view; (11) posterior view.

Wilbernia species from the Sunwaptan Stage, St. Charles Formation, Smithfi... Open Access

Published: 01 July 2024
Figure 20. Wilbernia species from the Sunwaptan Stage, St. Charles Formation, Smithfield Canyon, Utah. All specimens are from USNM loc. 44303. ( 1–3 ) Wilbernia aff. W. pero (Whitfield, 1880 ), partial, exfoliated cranidium USNM 781843: ( 1 ) dorsal view; ( 2 ) lateral view; ( 3 ) anterior
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Noelaspis? sp. from the Sunwaptan Stage, St. Charles Formation, Smithfield Canyon, Utah. All specimens are from USNM loc. 44302. (1) Exfoliated cranidium USNM 775709. (2–4) Exfoliated cranidium USNM 775708: (2) dorsal view; (3) anterior view; (4) oblique view. (5) Exfoliated partial pygidium USNM 775712. (6) Exfoliated hypostome USNM 775710. (7) Inverted photograph of partial pygidium USNM 775711. (1–4, 6) Specimens use the 4 mm scale bar; (5, 7) specimens use the 2 mm scale bar.

Noelaspis ? sp. from the Sunwaptan Stage, St. Charles Formation, Smithfield... Open Access

Published: 01 July 2024
Figure 22. Noelaspis ? sp. from the Sunwaptan Stage, St. Charles Formation, Smithfield Canyon, Utah. All specimens are from USNM loc. 44302. ( 1 ) Exfoliated cranidium USNM 775709. ( 2–4 ) Exfoliated cranidium USNM 775708: ( 2 ) dorsal view; ( 3 ) anterior view; ( 4 ) oblique view. ( 5
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Trilobites from the Taenicephalus Biozone, Sunwaptan Stage, St. Charles Formation, Smithfield Canyon, Utah. All specimens are from USNM loc. 44302, in dorsal view. (1–10, 12–14) Taenicephalus westropi Chatterton and Gibb, 2016: (1) mostly exfoliated cranidium USNM 781844; (2, 3) part, counterpart of exfoliated cranidium USNM 781848, inverted photograph of internal mold; (4) exfoliated cranidium USNM 781847; (5) exfoliated cranidium USNM 781845; (6, 7) part, counterpart of exfoliated cranidium USNM 781852; (8) testate librigena USNM 781850; (9) exfoliated librigena USNM 781849; (10) mostly exfoliated cranidium USNM 781846; (12) exfoliated pygidium USNM 781854; (13) exfoliated pygidium USNM 781853; (14) exfoliated pygidium USNM 781855. (11) Kendallina sp. indet. exfoliated cranidium USNM 781851. (1–10) Specimens use the 2 mm scale bar; (11–14) specimens use the 1 mm scale bar.

Trilobites from the Taenicephalus Biozone, Sunwaptan Stage, St. Charles F... Open Access

Published: 01 July 2024
Figure 23. Trilobites from the Taenicephalus Biozone, Sunwaptan Stage, St. Charles Formation, Smithfield Canyon, Utah. All specimens are from USNM loc. 44302, in dorsal view. ( 1–10, 12–14 ) Taenicephalus westropi Chatterton and Gibb, 2016 : ( 1 ) mostly exfoliated cranidium USNM 781844; ( 2
Journal Article

Left behind – delayed extinction and a relict trilobite fauna in the Cambrian–Ordovician boundary succession (east Laurentian platform, New York) Available to Purchase

ED LANDING, STEPHEN R. WESTROP, BJÖRN KRÖGER, ADAM M. ENGLISH
Published: 19 November 2010
Geological Magazine (2011) 148 (4): 529–557.
DOI: https://doi.org/10.1017/S0016756810000919
...ED LANDING; STEPHEN R. WESTROP; BJÖRN KRÖGER; ADAM M. ENGLISH Abstract Two completely dissimilar faunal changes occur between the Sunwaptan and Skullrockian Stages (Ptychaspid and Symphysurid ‘Biomeres’) in the uppermost Cambrian on the east Laurentian craton. An undolomitized section in the Little...
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Locality map and stratigraphic columns for the interval of the upper Downes Point Member that yielded Steptoean boulders (modified from Westrop and Eoff 2023). Ages of boulders from agnostid and trilobite faunas are indicated by the abbreviations, St (Steptoean) and Sw (Sunwaptan; age data from Ludvigsen et al. (1989), fig. 10). Boulders that are among those analyzed in this paper are indicated by bold font. Note that boulders from the entire Steptoean (CH 48–66) are mixed together in the amalgamated debris flow conglomerates at the top of bed 5 of the Downes Point Member at Cow Head (lower part of the Cow Head North–Point of Head section of James and Stevens (1986), pp. 103–109). At Hickey Cove (lower part of the Broom Point North section of James and Stevens (1986), pp. 123–126), conglomerates with Steptoean boulders alternate with conglomerates that yield Sunwaptan boulders; Steptoean and Sunwaptan boulders may be mixed together in some conglomerates (e.g., boulders HC 117 and HC 119).

Locality map and stratigraphic columns for the interval of the upper Downes... Available to Purchase

Published: 22 September 2023
Fig. 2. Locality map and stratigraphic columns for the interval of the upper Downes Point Member that yielded Steptoean boulders (modified from Westrop and Eoff 2023 ). Ages of boulders from agnostid and trilobite faunas are indicated by the abbreviations, St (Steptoean) and Sw (Sunwaptan; age
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Correlation of zonations for the Steptoean–Sunwaptan boundary interval in Laurentia (Nevada and Utah; Westrop and Adrain, 2007) and the Sackian of the Karatau-Naryn Terrane (Kazakhastan; Ergaliev and Ergaliev, 2008; Ergaliev et al., 2009), showing relative stratigraphic ranges of the agnostoid arthropods Biciragnostus and Kormagnostella, and the trilobite Irvingella. The zonations are aligned using the first and last appearances of Irvingella. Note that Biciragnostus and Kormagnostella appear later in Laurentia, at a level that may correlate closely with the base of the Sunwaptan regional stage. Using the highest occurrence of Irvingella as a guide, Biciragnostus may disappear at a horizon that correlates near the top of the Irvingella major Zone of Laurentia, and the last occurrence of Kormagnostella may correlate near the base of this zone. In Laurentia, the lower and upper boundaries of the I. major Zone record pulses of trilobite extinction at a “biomere” event (Westrop and Cuggy, 1999).

Correlation of zonations for the Steptoean–Sunwaptan boundary interval in L... Available to Purchase

Published: 01 September 2013
Figure 2 Correlation of zonations for the Steptoean–Sunwaptan boundary interval in Laurentia (Nevada and Utah; Westrop and Adrain, 2007 ) and the Sackian of the Karatau-Naryn Terrane (Kazakhastan; Ergaliev and Ergaliev, 2008 ; Ergaliev et al., 2009 ), showing relative stratigraphic ranges
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Measured section from highest Sunwaptan and basal Skullrockian part of the Conococheague Formation. Peritidal cycles are shown with arrows; the rest of the section is possibly noncyclic. Cv  =  cover, Ss  =  Sandstone; Lm  =  planar microbial laminites; Rc  =  ribbon carbonate; Gr  =  grainstone, Fp  =  flat-pebble conglomerate, Th  =  thrombolite.

Measured section from highest Sunwaptan and basal Skullrockian part of the ... Available to Purchase

Published: 01 April 2012
F ig 8— Measured section from highest Sunwaptan and basal Skullrockian part of the Conococheague Formation. Peritidal cycles are shown with arrows; the rest of the section is possibly noncyclic. Cv  =  cover, Ss  =  Sandstone; Lm  =  planar microbial laminites; Rc  =  ribbon carbonate; Gr