Late Cambrian (Furongian; Paibian, Steptoean) agnostoid arthropods from the Cow Head Group, western Newfoundland

Abstract

Nine agnostoid species from late Cambrian (Paibian: Steptoean) boulders from the Cow Head Group in western Newfoundland fall into three biostratigraphically distinct faunas. The Glyptagnostus reticulatus Fauna contains only the eponymous species and correlates with the lower part of the Paibian and the basal Steptoean of North America. The “Innitagnostus” inexpectans Fauna is more diverse and likely correlates into part of the lower Steptoean Aphelaspis Zone of western North America. The youngest fauna, the Acmarhachis kindlei n. sp. Fauna, also includes species of Homagnostus and Pseudagnostus, as well as a second new species of Acmarhachis, A. whittingtoni. It probably correlates with the Dunderbergia Zone (mid-Pabian and mid-Steptoean) of the western United States. The Laurentian species Acmarhachis typicalis Resser (1938) and A. acuta (Kobayashi, 1938) are evaluated from restudy of type material, and types of “Innitagnostus” inexpectans (Kobayashi, 1938) from British Columbia are also reillustrated.

The mid-Cambrian (Series 3, Guzhangian; Marjuman) trilobite Deiracephalus Resser, 1935, from western Newfoundland

“…Shelf-derived boulders accumulated as debris flows in a continental slope setting (James and Stevens 1986) to be later emplaced on the shelf during the orogeny (Lavoie et al 2003). This paper continues a long-term project to document the diverse trilobites and agnostoid arthropods of the Shallow Bay Formation (Ludvigsen et al 1989;Westrop et al 1996;Westrop and Ludvigsen 2000;Westrop et al 2008;Westrop and Eoff 2012;Westrop and Dengler 2014). Kindle (1982) assigned faunas that include Deiracephalus to his Zone 5, which likely correlates with the late Guzhangian (late Marjuman) Cedaria prolifica and C. brevifrons zones of the Mackenzie Mountains (Pratt 1992; note that this interval is entirely younger than the C. prolifica Zone as proposed by Babcock et al 2014), and the Crepicephalus Zone of the traditional North American zonation (Westrop et al 1996).…”

A Glyptagnostus reticulatus trilobite faunule from the Cambrian of the Northern Qilian Mountains, northwest China, and its paleogeographical implications

“…28, figs. 5, 7.2012 Glyptagnostus reticulatus ; Westrop and Eoff, p. 235, fig. 22.9–22.15.2012 Glyptagnostus reticulatus ; Ahlberg and Terfelt, fig.…”

“…This genus is controversial currently. Some workers regarded it as a junior synonym of Agnostus or Micragnostus (e.g., Robison, 1994; Peng and Robison, 2000; Høyberget and Bruton, 2008), whereas others treated it as a separate genus (e.g., Shergold and Laurie, 1997; Laurie in Paterson and Laurie, 2004; Westrop and Eoff, 2012). In Innitagnostus , the glabella has an angulate recess at the base to accommodate the basal lobes, and lateral portions of glabellar M2 are commonly separated from the midmost glabella by weak longitudinal (exsag.)…”

“…1–10.2012 Agnostus inexpectans ; Schwimmer and Montante, p. 34, fig. 2.1.2012“ Innitagnostus” inexpectans ; Westrop and Eoff, p. 231, figs. 21, 22.1–22.8.…”

“…Cephalon (Westrop and Eoff, 2012, fig. 22.1–22.3, GSC12006), locality P6/6, British Columbia, Furongian, “ Taenicephalus ”- (= Taenicephalites ) bearing black limestone.…”