Abstract
AbstractA diverse assemblage of moderately well-preserved radiolarians occurs in the Ordovician cherts of the Crawford Group in the Southern Uplands terrane of the Scottish borders. A total of 8 genera and 11 species are described. Taxa present correlate to the Middle Ordovician Pygodus anserinus biozone. Key species identified include: Proventocitum procerulum, Inanigutta gansuensis, Inanigutta sp. cf. I. complanata, Inanibigutta sp. cf. I. verrucula, Inanibigutta sp. cf. I. pinglianensis, ?Inanibigutta inconstans, ?Inanihella penrosei, Haplentactinia armillata, ?Oriundogutta ramificans and Syntagentactinia sp. A new species Haplotaeniatum albaensis is introduced here and described on the basis of details of skeletal architecture observed using microcomputed tomography, demonstrating the potential of this technique as a tool for improving the understanding of radiolarian taxonomy.
Highlights
Hinde (1890) first described radiolarians from the Southern Uplands of Scotland where they occur in a zone of red and green ribbon-bedded and massive grey cherts, mudstones and shales tectonically intercalated between Llandeilian and Caradocian graptolitic shale beds
More than 100 years later, Aitchison (1998) examined radiolarians extracted from red cherts of the nearby Ballantrae Complex using scanning electron microscopy (SEM)
We examined samples collected from outcrops of the Crawford Group in both the Hawkwood Burn and the Leadhills
Summary
Hinde (1890) first described radiolarians from the Southern Uplands of Scotland where they occur in a zone of red and green ribbon-bedded and massive grey cherts, mudstones and shales tectonically intercalated between Llandeilian and Caradocian graptolitic shale beds He reported and illustrated various forms, providing the first contribution to studies of lower Palaeozoic radiolarians. The faunas present were tentatively assigned to the upper Llanvirn – Caradoc Haplentactinia juncta – Inanigutta unica assemblage according to Nazarov’s (1988) biozonation They were considered to show affinity with a lower Caradocian radiolarian assemblage reported by Wang (1993) from the Pingliang Formation in Gansu Province, China. We discuss revised systematics for the taxa we recovered, introduce a new species with the aid of microcomputed tomography (micro-CT) and recognize six additional forms that have not previously been described from the Southern Uplands, but are known from Middle and Upper Ordovician localities elsewhere
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