Micro-CT study of Middle Ordovician Spumellaria (radiolarians) from western Newfoundland, Canada

Abstract

A new, previously undescribed Middle Ordovician (middle Darriwilian: Dw2) radiolarian assemblage has been recovered from the Table Cove Formation at Piccadilly Quarry, western Newfoundland. Constituents of the fauna described herein are both distinctive and exceptionally well preserved. Three-dimensional X-ray micro-computed tomography (μ-CT) is used to make a detailed examination of four key spumellarian specimens. This technology enables visualization of hitherto ambiguous details of the internal morphologies of key lower Paleozoic taxonomic groups, among which a lack of knowledge has impeded resolution of higher taxonomic rankings.

Middle Ordovician (Darriwilian) radiolarians from the Crawford Group, Scotland

“…One specimen with an uncertain taxonomic affiliation, here described as Haplotaeniatum albaensis, was examined using the Zeiss Xradia Versa XRM-500 high-resolution scanner at the Julius Kruttschnitt Mineral Research Centre, The University of Queensland, following the method developed by Kachovich et al (2019). Prior to scanning, machine parameters and configuration requirements were set according to the standard set-up developed by Kinney & Nichols (1992).…”

“…Multiple studies have questioned the validity of the number of spheres and spines as a diagnostic feature, and some researchers claim that the presence or absence of these features relate to ontogeny (Noble & Aitchison, 1995;Danelian & Popov, 2003;Suzuki, 2006;Maletz, 2011; S Kachovich, unpub. PhD thesis, The University of Queensland, 2018; Kachovich & Aitchison, 2020). This is evident from the variations in the shell dimensions and numbers of spines reported in many of the studies that have reported inaniguttids (Nazarov & Popov, 1980;Nazarov & Ormiston, 1984, 1993Nazarov, 1988;Wang, 1993;Li, 1995; Danelian & Clarkson, 1998;Danelian, 1999;Danelian & Floyd, 2001;Noble & Webby, 2009;Pouille et al 2013).…”

Middle Ordovician (middle Darriwilian) Archaeospicularia and Entactinaria (radiolarians) from the Table Cove Formation, Piccadilly Quarry, Newfoundland, Canada

“…Co-occurring conodonts allow correlation to the late Dw2 Histiodella kristinae subzone (Stouge, 1984).

Figure 1.Locality map showing position of study area (after Cooper et al, 2001; Kachovich and Aitchison, 2020). Inset map shows Port au Port Peninsula's location in relation to the rest of Newfoundland.

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“…In order to fully document a well-preserved radiolarian fauna from the middle Darriwilian Table Cove Formation in Newfoundland, this paper is intended to complement earlier work of Kachovich and Aitchison (2020) that described spumellarian radiolarians from the same location. Archaeospicularid and entactiniid radiolarians, together with forms that remain in open nomenclature, are described herein.…”

“…Radiolarian faunas have been reported from Ordovician strata globally from North and South America, Spitsbergen, Scotland, Russia, China, and Australia (see Danelian et al, 2017 and references therein). Documentation of Middle Ordovician (Darriwilian) radiolarians has been presented from Newfoundland (Kachovich and Aitchison, 2020), Argentina (Maletz et al, 2009), Kazakhstan (Nazarov, 1975; Nazarov et al, 1977; Nazarov and Ormiston, 1993; Pouille et al, 2013, 2014b), Scotland (Danelian and Clarkson, 1998; Danelian, 1999; Danelian and Floyd, 2001; Danelian et al, 2013; Perera et al, 2020), and China (Li, 1995; Buckman and Aitchison, 2001; Yi et al 2018).…”