Journal of Paleontology, 91(5), 2017, p. 883–901 Copyright © 2017, The Paleontological Society 0022-3360/17/0088-0906 doi: 10.1017/jpa.2017.8


Small shelly fossils from the Montezuman–Delamaran of the Great Basin in Nevada and California


Thomas Wotte1 and Frederick A. Sundberg2


1Institut für Geologie und Mineralogie, Universität zu Köln, Zülpicher Str. 49a, D-50674 Köln, Germany ⟨thomas.wotte@uni-koeln.de⟩ 2821 E. Pine Ln., Show Low, AZ 85901, USA ⟨freddeb85@cableone.net⟩


Abstract.—The mixed carbonate-siliciclastic successions of the Cambrian Series 2–Cambrian Series 3 interval of the Great Basin are well investigated in respect to their trilobite and brachiopod fauna. In contrast, the small shelly fossils have been mostly unreported. Nine sections in eastern California and southern Nevada have produced a small shelly assemblage of low diversity, which likely reflects non-phosphatization and loss of originally calcareous remains. From the Montezuman–Delamaran stages we report Anabarella chelata Skovsted, 2006a, Costipelagiella nevadense Skovsted, 2006a, Pelagiella aff. P. subangulata (Tate, 1892), Microcornus sp., Parkula sp., Hyolithellus? sp., Allonia sp., Chancelloria sp., Archiasterella cf. A. hirundo Bengtson in Bengtson et al., 1990, Archaeooides cf. A. granulatus Qian, 1977, and undefined echinoderms and helcionelloid molluscs. The lower part of the Montezuman Stage deliv- ered a number of lobopodian sclerites as Microdictyon rhomboidale Bengtson, Matthews, and Missarzhevsky, 1986, Microdictyon montezumaensis n. sp., and Microdictyon cuneum n. sp. The occurrence of P. aff. P. subangulata and species of Microdictyon in the lower Montezuman Stage offers a fundamental potential for correlation with the base of Cambrian Series 2/Stage 3 of South China, Siberia, and Avalonia.


Introduction


The Great Basin of western United States contains the most complete and well-exposed sections covering the Cambrian Series 2–Series 3 interval (Montezuman–Marjuman stages of the Laurentian nomenclature; Palmer, 1998). These highly fossiliferous, mixed carbonate-siliciclastic successions have been extensively investigated for their trilobite and brachiopod faunas (e.g., Rowell 1966, 1977, 1980; Rowell and Henderson, 1978; Palmer and Halley, 1979; Sundberg and McCollum, 1997, 2000, 2003a, b; Hollingsworth 2005, 2011a, b; Streng and Holmer, 2006; Sundberg, 2011; Webster, 2011a). However, other faunal elements, especially small shelly fossils (SSFs), are generally unconsidered. These SSFs provide important infor- mation for biostratigraphic, depositional environment, and paleoecologic reconstructions (e.g., Geyer, 1986; Elicki, 1994, 2005, 2006; Geyer and Shergold, 2000; Gubanov, 2002; Steiner et al., 2007). Few, non-brachiopod, SSFs have been reported in detail


Furthermore, the helcionelloid molluscs Anabarella chelata Skovsted, 2006a and Costipelagiella nevadense Skovsted, 2006a, the hyolith Parkula esmeraldina Skovsted, 2006a, and remains of echinoderms, chancelloriids, and sponges occur in the uppermost Dyeran Stage from the basal Emigrant Formation of Split Mountain (Fig. 1; Skovsted, 2006a). The lower Cambrian hyolith fauna originally described by Walcott (1886) and Resser (1938) from Nevada were reinvestigated by Malinky (1988).


Most recent report of SSFs from the Great Basin only


from the Great Basin. Tubes of uncertain affinity and the hyolith Salanytheca sp. occur in the pre-trilobitic Cambrian Deep Spring Formation of western Nevada and eastern California (Signor et al., 1987). The agglutinated protist Platysolenites antiquissimus Eichwald, 1860, chancelloriid sclerites, helico- placoid ossicles, and hyoliths occur in the Montezuman Stage of Indian Springs Canyon (Fig. 1; Streng et al., 2005; English and Babcock, 2010). Hyolithellus insolitus Grigorieva in Voronin et al., 1982, Sphenotallus sp., echinoderm ossicles, and sponge spicules were described from the lower Dyeran Harkless Formation of Gold Point (Fig. 1; Skovsted and Holmer, 2006).


mentioned their presence without any illustration, systematic documentation, and/or detailed stratigraphic distribution. Hollingsworth (2011b) and Hollingsworth and Babcock (2011) reported the hyolith “Ladatheca” cylindrica Grabau, 1900, orthothecid hyoliths, and the bradoriid Dielymella? Ulrich and Bassler, 1931 from the Montezuman Stage and the lower unnamed stage of the Indian Springs Canyon and Montezuma Range sections (Fig. 1). Webster (2011c) mentioned pelagiellids, hyoliths, and chancelloriids from the upper Dyeran from a variety of sections in Nevada. Sundberg and McCollum (1997, 2003a) and McCollum et al. (2011) mentioned Stenothecoides elongata Walcott (1886) and Latouchella arguta Resser (1939) and hyoliths, echinoderms, and chancel- loriids from the lower Delamaran Stage of Nevada. The purpose of this report is to document a new small


shelly assemblage from a variety of Montezuman–Delamaran mixed carbonate-siliciclastic successions of eastern California and southern Nevada in order to increase the knowledge of the paleogeographic and biostratigraphic potential of these faunal elements.


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