Oryctocephalids (Corynexochida: Trilobita) of the Lower-Middle Cambrian boundary interval from California and Nevada

Abstract

Seven species of oryctocephalids occur in the Lower to Middle Cambrian boundary strata of the southern Great Basin. These include Oryctocephalites palmeri n. sp. and an Oryctocephalinae species from the uppermost Lower Cambrian (upper Olenellus Biozone); Oryctocephalus indicus (Reed, 1910), Microryctocara nevadensis n. gen. and n. sp., and Oryctocephalites rasettii n. sp. near the base of the Middle Cambrian (lower Plagiura Biozone); and Oryctocephalus primus Walcott, 1886, and Oryctocephalus nyensis Palmer, 1979, from slightly higher strata (upper Plagiura Biozone). Oryctocephalus and Oryctocephalites are emended based on a cladistic analysis of Oryctocephalinae Beecher, 1897.

The Henson Gletscher Formation, North Greenland, and its bearing on the global Cambrian Series 2–Series 3 boundary

“…It was identified only from the latest Dyeran Combined Metals Member with certainty, where it more or less co-occurs with Bathynotus (originally identified as B. holopygus (Hall, 1859) and revised to B. granulatus Lermontova, 1940 or regarded as undeterminable by Webster 2009), various species of olenellids, Crassifimbra walcotti (Resser, 1937), Crassifimbra? metalaspis (Sundberg & McCollum, 2000), and Oryctocephalites palmeri Sundberg & McCollum, 1997. In the Freuchen Land section Zacanthopsis blakeri sp.…”

“…Oryctocephalus indicus was introduced as Zacanthoides indicus from the Spiti region of the Tethyan Himalaya of northern India (Reed 1910) and is based on conspicuously distorted material (see Jell & Hughes 1997); in a strict sense the species cannot be identified from other areas without certain reservations despite the coincident "rediscovery" of the species by Jell & Hughes (1997), Sundberg & McCollum (1997) and Yuan et al (1997). Geyer (2006) emphasized that Reed (1910) in the same article in which he introduced Zacanthoides indicus described an "Oryctocephalus cf.…”

“…Together with comparable material recovered from the Emigrant Formation of the Split Mountain section and coeval strata of other sections in western Nevada (Sundberg & McCollum 1997, it has been used as the main key for (semi-)global correlation, although the assignment of the Laurentian material was temporarily challenged (e.g. Zhao et al 2004).…”

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

“…The Mule Spring Limestone is overlain by the siliciclastic and carbonate, partly highly condensed Emigrant Formation (uppermost Dyeran-Sunwaptan Stage) in western Nevada and by the Monola Formation in Death Valley National Park of eastern California (e.g., Palmer, 1971;Palmer and Halley, 1979;Sundberg, 2011;Sundberg et al, 2011). The Monola Formation is subdivided into a lower claystone portion with intercalated limestone and an upper limestone with minor siltstone intercalations (Sundberg and McCollum, 1997). Palmer and Halley, 1979;Sundberg andMcCollum, 2000, 2003b;Sundberg, 2011;Webster, 2011a).…”

“…These highly fossiliferous, mixed carbonate-siliciclastic successions have been extensively investigated for their trilobite and brachiopod faunas (e.g., Rowell 1966Rowell , 1977Rowell , 1980Rowell and Henderson, 1978;Palmer and Halley, 1979;Sundberg and McCollum, 1997, 2003aHollingsworth 2005Hollingsworth , 2011aStreng and Holmer, 2006;Sundberg, 2011;Webster, 2011a). However, other faunal elements, especially small shelly fossils (SSFs), are generally unconsidered.…”