Earliest Arenig radiolarians from the Cow Head Group, Western Newfoundland

A groundbreaking discovery of earliest Arenig radiolarians from the Cow Head Group in Gros Morne National Park, Newfoundland, reveals significant evolutionary shifts in radiolarian faunas. This study identifies two new assemblages comprising eight families, 13 genera, and 25 species, including 11 newly described species. Contrary to previous assumptions, the difference between pre-Arenigian and Arenigian radiolarian faunas is attributed to phylogenetic evolution rather than mass extinction. Key features distinguishing earliest Arenig assemblages include the development of a 'bandage' structure and multiple concentric shells with a proloculus or microsphere. The precise biostratigraphic age of one assemblage was confirmed using the index conodont Prioniodus adami from the Tetragraptus approximatus Graptolite Zone, marking the base of the Arenigian period.

Won, M.-Z., & Iams, W. J. (2011). Earliest Arenig radiolarians from the Cow Head Group, Western Newfoundland. Journal of Paleontology, 85(1), 156–177. https://doi.org/10.1666/10-102.1