Corynexochine trilobites of the Harkless Formation and Mule Spring Limestone (Cambrian Series 2, Stage 4), Clayton Ridge, Nevada

Abstract

Most Cambrian Series 2 faunas of Laurentia are dominated by olenelline trilobites; however, non-olenelline trilobites occur with the olenellines and sometimes dominate the assemblages. Reported here are such non-olenelline trilobites from the Harkless Formation and Mule Spring Limestone at Clayton Ridge, Nevada. At the bottom of the Saline Valley Tongue, Harkless Formation, are two assemblages that are characterized by corynexochines and/or ptychoparioids, with olenellines occurring as only rare components. The corynexochines present in these assemblages include Bonnia cf. B. brennus (Walcott, 1916), Ovatoryctocara cf. O. yaxiensis Yuan et al., 2009, Protoryctocephalus? aff. P.? arcticus Geyer and Peel, 2011, Ogygopsis sp. indet., and Oryctocephalops frischenfeldi Lermontova, 1940. These assemblages are from the mid-Dyeran Stage, below the lowermost zone in the upper Dyeran (Arcuolenellus arcuatus Biozone), and can be correlated to Series 2 Stage 4 (Cambrian) assemblages in Greenland, Siberia, and South China based on the corynexochines. Also in the Saline Valley Tongue and the overlying Mule Spring Limestone and lowermost Emigrant Formation are olenelloid-dominated assemblages that contain the corynexochines Bonnia columbensis Resser, 1936, Zacanthopsis aff. Z. levis (Walcott, 1886), and Z. sp. indet.

Trilobites of the Cranbrook Lagerstätte (Eager Formation, Cambrian Stage 4), British Columbia

“…Best's (1952a, b) previous identification of Bonnia columbensis from Cranbrook would imply a species-level correlation to (middle? to) upper Dyeran strata in the Canadian Rockies of British Columbia (Walcott, 1917;Rasetti, 1951), the Wernecke Mountains of Yukon Territory (Fritz, 1991), the Sekwi Formation of Yukon Territory (Fritz, 1972), and Clayton Ridge in Nevada (Sundberg and Webster, 2021). However, none of those previous identifications is supported herein, and the correlations that they implied must therefore be reconsidered.…”

“Ptychoparioid” trilobites of the Harkless Formation and Mule Spring Limestone (Cambrian Series 2, Stage 4), Clayton Ridge, Nevada

“…1,2). This paper is complimentary to a report on the corynexochines and biostratigraphy of the same interval (Sundberg and Webster, 2021). Some of the new collections contain abundant specimens, including articulated exoskeletons and/or associated sclerites.…”

“…Material.-The trilobites from the lowest limestones of the Saline Valley Tongue of the Harkless Formation reported here are preserved as finely silicified specimens in laminated clayey micrites. The methods used to prepare these silicified specimens are presented in Sundberg and Webster (2021). Other nonsilicified specimens from the Harkless Formation, Mule Spring Limestone, and Emigrant Formation were mechanically prepared.…”

“…This paper focuses on “ptychoparioids” from the mid to upper Dyeran succession, comprising the uppermost Harkless Formation, Mule Spring Limestone, and lowermost Emigrant Formation in the Split Mountain area. Much of the geologic background presented here is more fully documented in Sundberg and Webster (2021).…”

“…Information for some taxa from the Mule Spring Limestone and the lowermost Emigrant Formation is derived from Sundberg and McCollum (2003b) and Webster (2011b, c). Olenelloid and corynexochine trilobite stratigraphic ranges are from Sundberg and Webster (2021). Blue line represents the base of the global Miaolingian Series; red line represents the base of the Laurentian Lincolnian Series.…”