Marjum Formation

The Marjum Formation is a Cambrian geological formation that overlies the Wheeler Shale in the House Range, Utah.[1][3] It is named after its type locality, Marjum Pass, and was defined in 1908.[2] The formation is known for its occasional preservation of soft-bodied tissue, and is slightly younger than the Burgess Shale,[4] falling in the Ptychagnostus praecurrens trilobite zone.[5]

Marjum Formation
Stratigraphic range: Middle Cambrian
Notch Peak Sill intruding into the layers of white marble and grey argillite of the Marjum Formation
TypeGeological formation
OverliesWheeler Shale
ThicknessUp to 430 meters[1]
Lithology
Primarylimestone
Othershale, metasedimentary rocks
Location
Region Utah
Country USA
ExtentHouse Range
Type section
Named forMarjum Pass[2]
Named byCharles D. Walcott
Year defined1908[2]

Fossil content
Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Ambulacrarians
Ambulacrarians reported from the Marjum Formation
GenusSpeciesPresence MaterialNotesImages
Castericystis C. vali Numerous specimens.[6] A solutan.
Eldonia E. ludwigi Marjum Pass (Ptychagnostus punctuosus Zone).[7] SM X.50204.1 (part) & SM X.50204.2 (counterpart).[7] A cambroernid.
Marjumicystis M. mettae 7 specimens.[6] An eocrinoid.
Mastigograptus M. sp. A single specimen.[8] A mastigograptid graptolite.
Totiglobus T.? lloydi Locality 811.[9] 1 specimen (USNM 172047).[9] An edrioasteroid.

Arthropods
Arthropods reported from the Marjum Formation
GenusSpeciesPresence MaterialNotesImages
Anomalocaris A. nathorsti Sponge Gully.[10] Partial body (USNM 374593).[10] Species moved to the genus Peytoia.
Asaphiscus A. wheeleri Bathyuriscus fimbriatus Subzone.[11] A ptychopariid trilobite.
Baltagnostus B. eurypyx All subzones of the Bolaspidella Zone.[11] Multiple specimens.[11] A diplagnostid trilobite.
Bathyuriscidella B. aff. B. amplicauda Bolaspidella contracta Subzone.[11] 3 pygidia.[11] A dolichometopid trilobite.
Bathyuriscus B. elegans Bolaspidella contracta Subzone.[11] Numerous specimens.[11] A dolichometopid trilobite.
B. fimbriatus Bathyuriscus fimbriatus & lower Bolaspidella contracta Subzone.[11] Numerous specimens.[11] A dolichometopid trilobite.
Bolaspidella B. contracta Bolaspidella contracta & lower Lepojyge calva Subzones.[11] A menomoniid trilobite.
B. housensis Bathyuriscus fimbriatus Subzone.[11] A menomoniid trilobite.
B. jarrardi Localities 347, 391, and 716 (mid-Bolaspidella Zone).[12] Multiple specimens.[12] A menomoniid trilobite.
Branchiocaris B. pretiosa Sponge Gully.[10][13] 3 specimens.[10] A hymenocarine.
Buccaspinea B. cooperi Kells Knolls locality.[14] An almost complete specimen (BPM 1108).[14] A hurdiid, originally reported as Hurdia sp.
Burlingia B. halgedahlae Localities 347 and 716 (mid-Bolaspidella Zone).[12] Multiple specimens.[12] A burlingiid trilobite.
Caryosyntrips C. camurus 'Red Wash' locality.[14] 2 isolated frontal appendages.[14] A radiodont of uncertain classification.
Cotalagnostus C. laevus Bolaspidella contracta Subzone.[11] Over 50 specimens.[11] A diplagnostid trilobite.
C. sp. Bolaspidella contracta Subzone.[11] A pygidium. A diplagnostid trilobite.
Dicranocaris D. guntherorum Red Wash, Modocia Flats & Sponge Gully.[13] 4 specimens.[13] An arthropod of uncertain classification.
Dytikosicula D. desmatae West of Delta, House Range.[7] 1 specimen (SM X.50203).[7] A putative megacheiran.
Elrathia E. alapyge Bolaspidella contracta & Lejopyge calva Subzones.[11] Numerous specimens.[11] A ptychopariid trilobite.
E. marjumi Bathyuriscus fimbriatus & Bolaspidella contracta Subzones.[11] Numerous specimens.[11] A ptychopariid trilobite.
Emeraldella E.? sp. Red Wash.[10] Part & counterpart (KUMIP 204791).[10] An artiopod.
Hemirhodon H. amplipyge Bolaspidella contracta Subzone.[11] 14 incomplete specimens.[11] A dolichometopid trilobite.
Holteria H. problematica Marjum Pass (Lejopyge calva Subzone).[11] A pygidium.[11] A corynexochid trilobite.
Homagnostus H. incertus Bolaspidella contracta Subzone.[11] Multiple specimens.[11] An agnostid trilobite.
Hypagnostus H. parvifrons All subzones of the Bolaspidella Assemblage Zone.[11] Numerous specimens.[11] A diplagnostid trilobite.
Itagnostus I. interstrictus House Range.[15] A peronopsid trilobite originally reported as Peronopsis interstricta.
Leanchoilia L.? cf. protogonia Sponge Gully.[13] Part & counterpart of a complete specimen (UU 06011.01).[13] A megacheiran.
Lejopyge L. calva Marjum Pass (Lejopyge calva Subzone).[11] Numerous specimens.[11] A ptychagnostid trilobite.
Linguagnostus L. perplexus Bolaspidella contracta Subzone.[11] Over 20 specimens.[11] A diplagnostid trilobite.
Marjumia M. callas Bolaspidella contracta Subzone.[11] A marjumiid trilobite.
M. typa Bolaspidella contracta Subzone.[11] A marjumiid trilobite.
Modocia M. laevinucha Bathyuriscus fimbriatus & Bolaspidella contracta Subzones.[11] Many specimens.[11] A marjumiid trilobite.
M. nuchaspina Bolaspidella contracta Subzone.[11] A marjumiid trilobite.
M. typicalis 50 or more specimens.[11] A marjumiid trilobite.
Naraoia N. compacta Sponge Gully.[16] 4 specimens.[16] A naraoiid.
Neolenus N. inflatus East of Antelope Springs.[17] Multiple specimens & fragments.[17] A trilobite.
N. intermedius East of Antelope Springs.[17] A trilobite.
N. intermedius pugio East of Antelope Springs.[17] 4 specimens of a pygidium.[17] A trilobite.
N. superbus East of Antelope Springs.[17] Multiple specimens & fragments.[17] A trilobite.
Nettapezoura N. basilika Sponge Gully.[13] An arachnomorph.
Olenoides O. decorus Bolaspidella contracta Subzone.[11] 7 specimens.[11] A dorypygid trilobite.
O. inflatus Bolaspidella contracta Subzone.[11] A dorypygid trilobite.
O. marjumensis Bolaspidella contracta Subzone.[11] A dorypygid trilobite.
O. pugio Bolaspidella contracta Subzone.[11] Numerous specimens.[11] A dorypygid trilobite.
O. superbus Bolaspidella contracta Subzone.[11] 7 specimens.[11] A dorypygid trilobite.
Pahvantia P. hastata Precise localities unknown.[14] 3 specimens.[14] A hurdiid.
Peronopsis P. interstricta House Range.[15] Numerous specimens.[11] Reassigned to the genus Itagnostus.
P. segmenta House Range.[15] Multiple specimens.[11] A peronopsid trilobite.
Perspicaris P.? ellipsopelta Ptychagnostus punctuosus Zone.[18] Valves & carapaces.[18] A bivalved arthropod.
Peytoia P. nathorsti Sponge Gully.[10] Partial body (USNM 374593) & partial mouthpart (KUMIP 314095).[19] A hurdiid, formerly named Anomalocaris nathorsti.
Ptychagnostus P. akanthodes Bolaspidella contracta Subzone.[11] Numerous specimens.[11] A ptychagnostid trilobite.
P. atavus House Range.[15] A ptychagnostid trilobite.
P. hybridus Bolaspidella contracta Subzone.[11] About 10 specimens.[11] A ptychagnostid trilobite.
P. richmondensis Bathyuriscus fimbriatus Subzone.[11] Numerous specimens.[11] A ptychagnostid trilobite.
P. sp. Bolaspidella contracta Subzone.[11] At least 5 pygidia. A ptychagnostid trilobite.
Trymataspis T. depressa Bolaspidella contracta Subzone.[11] Over 30 specimens.[11] A lonchocephalid trilobite.
T. lomaleie Bolaspidella contracta Subzone.[11] 10 cranidia.[11] A lonchocephalid trilobite.
T. pristina Bolaspidella contracta Subzone.[11] Over 20 cranidia.[11] A lonchocephalid trilobite.
Tuzoia T. guntheri Ptychagnostus punctuosus Zone.[18] Multiple valves & carapaces.[18][20] A hymenocarine.
Utagnostus U. trispinulus Bolaspidella contracta & Lejopyge calva Subzones.[11] Multiple specimens.[11] An agnostid trilobite.
Utaspis U. marjumensis House Range & Wheeler Amphitheater.[11] A ptychopariid trilobite.
Zacanthoides Z. sp. Wheeler Amphitheater (Bolaspidella contracta Subzone).[11] A cranidium.[11] A zacanthoidid trilobite.

Chancelloriids
Chancelloriids reported from the Marjum Formation
GenusSpeciesPresence MaterialNotesImages
Chancelloria C. sp. Bathyuriscus fimbriatus & Bolaspidella contracta Subzones.[11] About 20 spicules.[11] A chancelloriid.

Chordates
Chordates reported from the Marjum Formation
GenusSpeciesPresence MaterialNotesImages
Megasiphon M. thylakos House Range.[21] One specimen (UMNH.IP.6079).[21] A tunicate.

Cnidarians

Moon, Caron & Moysiuk (2023) considered these fossils would be ctenophores instead.[22]

Cnidarians reported from the Marjum Formation
GenusSpeciesPresence MaterialNotesImages
Coronatae? Indeterminate Sponge Gully.[23] 1 specimen (UU07021.05).[23] A scyphozoan jellyfish, may be referrable to the crown jellyfish family.
Cubozoa? Indeterminate Sponge Gully.[23] 2 specimens (UU07021.01 & UU07021.02).[23] Specimens possibly referrable to box jellyfish.
Narcomedusae? Indeterminate Sponge Gully.[23] 5 specimens (UU07021.03, UU07021.04, UU07021.06, UU07021.07 & UU07021.08).[23] A hydrozoan tentatively assigned to this family.
Semaeostomeae? Indeterminate Sponge Gully.[23] 2 specimens (UU07021.09 & UU07021.10).[23] A scyphozoan jellyfish tentatively assigned to this family.

Ctenophores
Ctenophores reported from the Marjum Formation
GenusSpeciesPresence MaterialNotesImages
Ctenorhabdotus C. campanelliformis House Range (likely from the lower Ptychagnostus punctuosus Zone).[24] 1 specimen (UMNH.IP.6125).[24] A ctenophore.
Thalassostaphylos T. elegans House Range (lower Ptychagnostus punctuosus Zone).[24] 1 specimen (UMNH.IP.6086).[24] A ctenophore.

Lophotrochozoans
Lophotrochozoans reported from the Marjum Formation
GenusSpeciesPresence MaterialNotesImages
Acrothele A. subsidua Bathyuriscus-Elrathina & Bolaspidella Zones.[11] A brachiopod.
Helcionella "H." arguta Bathyuriscus fimbriatus & Bolaspidella contracta Subzones.[11] More than 100 specimens.[11] A helcionellid.
Hyolithes H. sp. All subzones of the Bolaspidella Zone.[11] More than 100 specimens.[11] A hyolith.
Lingulella L. sp. Bathyuriscus fimbriatus & Bolaspidella contracta Subzones.[11] An obolid brachiopod.
Micromitra M. modesta Multiple specimens.[11] A paterinide brachiopod.
Nisusia N. sulcata 18 specimens.[25] A kutorginate brachiopod.
Pegmatreta P. bellatula Bathyuriscus fimbriatus & Bolaspidella contracta Subzones.[11] Numerous specimens.[11] A brachiopod.
P. ophirensis All subzones of the Bolaspidella Zone.[11] A brachiopod.
Pelagiella P. sp. Bolaspidella contracta Subzone.[11] More than 50 internal molds.[11] A pelagiellid.
Prototreta P. attenuata Bathyuriscus-Elrathina Zone & Bolaspidella Zone.[11] A brachiopod.
P. mimica Bolaspidella contracta Subzone.[11] A brachiopod.
Stenothecoides S. elongata Bathyuriscus fimbriatus Subzone.[11] Over 30 valves.[11] A stenothecoid.

Scalidophorans
Scalidophorans reported from the Marjum Formation
GenusSpeciesPresence MaterialNotesImages
Arrakiscolex A. aasei Grey Marjum locality (Ptychagnostus punctuosus Zone).[26] Cuticle fragments.[26] A palaeoscolecid also known from the Upper Weeks Formation.
Ottoia O. prolifica Sponge Gully.[5] A complete individual (KUMIP 204770).[5] Referral of the specimen to this species is insecure, better classified as O.? sp.[26][27]
O.? sp. Sponge Gully.[26] A complete individual (KUMIP 204770).[26] A stem-priapulid, specimen formerly referred to Ottoia prolifica or Scathascolex minor.[26]
Scathascolex S. minor Sponge Gully.[5] A complete individual (KUMIP 204770).[5][28] Specimen reassigned to Ottoia? sp.[26]
Selkirkia S. willoughbyi Sponge Gully.[5] Tube with associated soft parts (KUMIP 204788).[5] A stem-priapulid.

Sponges
Sponges reported from the Marjum Formation
GenusSpeciesPresence MaterialNotesImages
Choia C. carteri Sponge Gulch.[29] A demosponge.
C. hindei Red Cliffs Wash.[29] 2 specimens & 3 other fragments.[29] A demosponge.
C. utahensis Sponge Gulch.[29] Several specimens.[29] A demosponge.
Diagoniella D. cyathiformis Red Cliffs Wash & Kells Knolls Gulch.[29] Numerous specimens.[29] A reticulosan.
D. hindei Sponge Gulch.[29] Approximately 40 specimens.[29] A reticulosan.
D. magna Kells Knolls Gulch (Bathyuriscus fimbriatus zone).[30] A fragment (USNM 535922).[30] A reticulosan.
D. sp. Sponge Gulch.[29] 2 large fragments.[29] A reticulosan.
Hamptonia H. bowerbanki Red Cliffs Wash & Sponge Gulch.[29] Multiple specimens.[29] A demosponge.
Hazelia H. palmata Near Marjum Pass.[31] One specimen.[31] A demosponge.
Hintzespongia H. bilamina Kells Knolls Gulch (Bathyuriscus fimbriatus zone).[29][30] Multiple specimens.[29][30] A reticulosan.
Hexactinellida Indeterminate Miscellaneous spicules.[11] Indeterminate glass sponges, originally reported as Hyalospongiae (now a junior synonym).
Kiwetinokia Drum Mountains.[29] 4 large slabs.[29] A reticulosan.
Leptomitus L. metta Red Cliffs Wash locality.[29] 22 specimens.[29] A demosponge.
Protospongia P.? elongata Sponge Gulch.[29] 1 specimen.[29] A reticulosan.
Testiispongia T. venula Sponge Gulch.[29] Several specimens.[29] A glass sponge.
Valospongia V. gigantis Sponge Gulch.[29] A reticulosan.
V.? gigantus Kells Knolls Gulch (Bathyuriscus fimbriatus zone).[30] A fragment (USNM 535917).[30] A reticulosan.

Vetulicolians
Vetulicolians reported from the Marjum Formation
GenusSpeciesPresence MaterialNotesImages
Skeemella S. clavula North of Red Wash (Ptychagnostus punctuosus Biozone).[32] 2 specimens (KUMIP 314102 & KUMIP 314103).[32] A banffid.

See also

References
  1. Foster, John; Gaines, Robert (October 2016). "Taphonomy and paleoecology of the "middle" Cambrian (Series 3) formations in Utah's West Desert: Recent finds and new data". Utah Geological Association Publication. 45: 291–336.
  2. Walcott, Charles D. (1910). "Nomenclature of some cambrian cordilleran formations". Smithsonian Miscellaneous Collections. 53 (1): 1–12.
  3. "Trilobites of The Marjum Formation".
  4. Robison, R. A. (1964). "Upper Middle Cambrian Stratigraphy of Western Utah". Geological Society of America Bulletin. 75 (10): 995–1010. Bibcode:1964GSAB...75..995R. doi:10.1130/0016-7606(1964)75[995:UMCSOW]2.0.CO;2. ISSN 0016-7606.
  5. Conway Morris, S.; Robison, R. A. (1986). "Middle Cambrian priapulids and other soft-bodied fossils from Utah and Spain". University of Kansas Paleontological Contributions. 117: 1–22. hdl:1808/3696.
  6. Ubaghs, G.; Robison, Richard A. (September 1985). "A homoiostelean and a new eocrinoid from the Middle Cambrian of Utah". University of Kansas Paleontological Contributions (115): 1–24.
  7. Conway Morris, Simon; Selden, Paul A.; Gunther, Glade; Jamison, Paul G.; Robison, Richard A. (May 2015). "New records of Burgess Shale-type taxa from the middle Cambrian of Utah". Journal of Paleontology. 89 (3): 411–423. doi:10.1017/jpa.2015.26. ISSN 0022-3360.
  8. LoDuca, Steven T.; Kramer, Anthony (March 2014). "Graptolites from the Wheeler and Marjum Formations (Cambrian, Series 3) of Utah". Journal of Paleontology. 88 (2): 403–410. doi:10.1666/12-096. ISSN 0022-3360.
  9. Sprinkle, James (January 1985). "New edrioasteroid from the Middle Cambrian of western Utah". University of Kansas Paleontological Contributions. 116: 1–4.
  10. Briggs, D. E. G.; Robison, Richard A. (January 1984). "Exceptionally preserved nontrilobite arthropods and Anomalocaris from the Middle Cambrian of Utah". University of Kansas Paleontological Contributions. 111: 1–23.
  11. Robison, Richard A. (1964). "Late Middle Cambrian Faunas from Western Utah". Journal of Paleontology. 38 (3): 510–566. ISSN 0022-3360.
  12. Robison, Richard A.; Babcock, Loren E. (2011-11-30). "Systematics, paleobiology, and taphonomy of some exceptionally preserved trilobites from Cambrian Lagerstätten of Utah". Paleontological Contributions (5): 1–47. doi:10.17161/PC.1808.8543. ISSN 1946-0279.
  13. Briggs, Derek E. G.; Lieberman, Bruce S.; Hendricks, Jonathan R.; Halgedahl, Susan L.; Jarrard, Richard D. (2008). "Middle Cambrian arthropods from Utah". Journal of Paleontology. 82 (2): 238. ISSN 0022-3360.
  14. Pates, Stephen; Lerosey-Aubril, Rudy; Daley, Allison C.; Kier, Carlo; Bonino, Enrico; Ortega-Hernández, Javier (2021-01-19). "The diverse radiodont fauna from the Marjum Formation of Utah, USA (Cambrian: Drumian)". PeerJ. 9: e10509. doi:10.7717/peerj.10509. ISSN 2167-8359. PMC 7821760. PMID 33552709.
  15. Robison, R. A. (1982). "Some Middle Cambrian Agnostoid Trilobites from Western North America". Journal of Paleontology. 56 (1): 132–160. ISSN 0022-3360.
  16. Robison, Richard A. (1984-07-24). "New Occurrences of the Unusual Trilobite Naraoia From the Cambrian of Idaho and Utah". University of Kansas Paleontological Contributions. 112: 1–8.
  17. Walcott, Charles D. (1908-04-25). "Cambrian Trilobites". Smithsonian Miscellaneous Collections. 53 (2): 14–52.
  18. Robison, Richard A.; Richards, B. C. (1981-12-16). "Large bivalve arthropods from the Middle Cambrian of Utah". University of Kansas Paleontological Contributions. 106: 1–19.
  19. Pates, Stephen; Daley, Allison C.; Lieberman, Bruce S. (January 2018). "Hurdiid radiodontans from the middle Cambrian (Series 3) of Utah". Journal of Paleontology. 92 (1): 99–113. doi:10.1017/jpa.2017.11. ISSN 0022-3360.
  20. Vannier, Jean; Caron, Jean-Bernard; Yuan, Jin-Liang; Briggs, Derek E. G.; Collins, Desmond; Zhao, Yuan-Long; Zhu, Mao-Yan (May 2007). "Tuzoia: Morphology and Lifestyle of a Large Bivaled Arthropod of the Cambrian Seas". Journal of Paleontology. 81 (3): 445–471. doi:10.1666/pleo05070.1. ISSN 0022-3360.
  21. Nanglu, Karma; Lerosey-Aubril, Rudy; Weaver, James C.; Ortega-Hernández, Javier (2023-07-06). "A mid-Cambrian tunicate and the deep origin of the ascidiacean body plan". Nature Communications. 14 (1): 3832. doi:10.1038/s41467-023-39012-4. ISSN 2041-1723. PMC 10325964.
  22. Moon, Justin; Caron, Jean-Bernard; Moysiuk, Joseph (2023-08-09). "A macroscopic free-swimming medusa from the middle Cambrian Burgess Shale". Proceedings of the Royal Society B: Biological Sciences. 290 (2004). doi:10.1098/rspb.2022.2490. ISSN 0962-8452. PMC 10394413. PMID 37528711.
  23. Cartwright, Paulyn; Halgedahl, Susan L.; Hendricks, Jonathan R.; Jarrard, Richard D.; Marques, Antonio C.; Collins, Allen G.; Lieberman, Bruce S. (2007-10-31). Humphries, Stuart (ed.). "Exceptionally Preserved Jellyfishes from the Middle Cambrian". PLoS ONE. 2 (10): e1121. doi:10.1371/journal.pone.0001121. ISSN 1932-6203. PMC 2040521. PMID 17971881.
  24. Parry, Luke A.; Lerosey-Aubril, Rudy; Weaver, James C.; Ortega-Hernández, Javier (2021-09-24). "Cambrian comb jellies from Utah illuminate the early evolution of nervous and sensory systems in ctenophores". iScience. 24 (9): 102943. doi:10.1016/j.isci.2021.102943. ISSN 2589-0042. PMC 8426560. PMID 34522849.
  25. Holmer, Lars E.; Popov, Leonid E.; Ghobadi Pour, Mansoureh; Claybourn, Tom; Zhang, Zhiliang; Brock, Glenn A.; Zhang, Zhifei (2018-01-09). "Evolutionary significance of a middle Cambrian (Series 3) in situ occurrence of the pedunculate rhynchonelliform brachiopod Nisusia sulcata". Lethaia. 51 (3): 424–432. doi:10.1111/let.12254. ISSN 0024-1164.
  26. Leibach, Wade; Lerosey-Aubril, Rudy; Whitaker, Anna; Schiffbauer, James; Kimmig, Julien (September 2021). "First palaeoscolecid from the Cambrian (Miaolingian, Drumian) Marjum Formation of western Utah". Acta Palaeontologica Polonica. 66. doi:10.4202/app.00875.2021.
  27. Smith, Martin R.; Harvey, Thomas H. P.; Butterfield, Nicholas J. (May 2015). Kouchinsky, Artem (ed.). "The macro‐ and microfossil record of the Cambrian priapulid Ottoia". Palaeontology. 58 (4): 705–721. doi:10.1111/pala.12168. ISSN 0031-0239.
  28. Smith, Martin R. (2015-10-15). Sigwart, Julia (ed.). "A palaeoscolecid worm from the Burgess Shale". Palaeontology. 58 (6): 973–979. doi:10.1111/pala.12210.
  29. Rigby, J. Keith (1983). "Sponges of the Middle Cambrian Marjum Limestone from the House Range and Drum Mountains of Western Millard County, Utah". Journal of Paleontology. 57 (2): 240–270. ISSN 0022-3360.
  30. Rigby, J. Keith; Church, Stephen B.; Anderson, Nicolle K. (2010). "Middle Cambrian Sponges from the Drum Mountains and House Range in Western Utah". Journal of Paleontology. 84 (1): 66–78. ISSN 0022-3360.
  31. Rigby, J. Keith; Gunther, Lloyd F.; Gunther, Freida (November 1997). "The first occurrence of the Burgess Shale demosponge Hazelia palmata Walcott, 1920, in the Cambrian of Utah". Journal of Paleontology. 71 (6): 994–997. doi:10.1017/S0022336000035976. ISSN 0022-3360.
  32. Kimmig, Julien; Leibach, Wade W.; Lieberman, Bruce S. (2020-05-30). "First occurrence of the problematic vetulicolian Skeemella clavula in the Cambrian Marjum Formation of Utah, USA". Carnets de géologie (Notebooks on geology). 20 (10): 215–221. doi:10.4267/2042/70836. hdl:1808/33460.
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