A diverse Upper Darriwilian radiolarian assemblage from the Shundy Formation of Kazakhstan: insights into late Middle Ordovician radiolarian biodiversity

Lauren Pouille,Taniel Danelian,Leonid E. Popov

doi:10.1144/jmpaleo2014-008

Lauren Pouille, Taniel Danelian + Show 1 more

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https://doi.org/10.1144/jmpaleo2014-008

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Abstract

Abstract. A diverse and well-preserved radiolarian assemblage was extracted from a carbonate sample of latest Darriwilian age from the Shundy Formation of the Aksuran Mountain (North Balkhash Region, Kazakhstan). The fauna is represented by 32 species or morphotypes which belong to nine genera, four families and two orders (Spumellaria and Entactinaria), including four new species described herein (Syntagentactinia? angulata n. sp. Pouille &amp; Danelian, Polyentactinia spinulenta n. sp. Pouille &amp; Danelian, Haplotaeniatum circulus n. sp. Pouille &amp; Danelian and H.? giganteum n. sp. Pouille &amp; Danelian). Representatives of the family Inaniguttidae are particularly abundant, representing c. 70% of the studied assemblage, especially genera Triplococcus and Inanihella that dominate the assemblage. Although the studied fauna contains both of the characteristic species and most of the genera of the previously defined Haplentactinia juncta–Inanigutta unica assemblage, differences in the assemblage structure are striking. The studied fauna also establishes that the two characteristic species of the Inanihella bakanasensis–Triplococcus akzhala assemblage are not restricted to the early–mid-Darriwilian, but their age range also extends to the latest Darriwilian.

Highlights

In spite of the major progress achieved recently in understanding the ‘Great Ordovician Biodiversification Event’ (Webby et al, 2004; Servais et al, 2010), our knowledge of the biodiversity and diversification dynamics of some biotic groups is still very fragmentary
Middle Ordovician radiolarian faunas recovered from carbonate sequences in Kazakhstan are of major significance for advancing our understanding of Ordovician Radiolarian biodiversity
Middle Ordovician radiolarian assemblages are known from siliceous sequences of Lower Palaeozoic orogenic belts (i.e. Scotland: Danelian & Clarkson, 1998; Danelian & Floyd, 2001; Kyrgyzstan: Danelian et al, 2011; China: Buckman & Aitchison, 2001), but they are less well preserved, due to differences in taphonomic history and laboratory processing

Summary

Introduction

In spite of the major progress achieved recently in understanding the ‘Great Ordovician Biodiversification Event’ (Webby et al, 2004; Servais et al, 2010), our knowledge of the biodiversity and diversification dynamics of some biotic groups is still very fragmentary. This is true for polycystine Radiolaria, a major component of the oceanic heterotrophic plankton in Early Palaeozoic marine ecosystems, from which only a few radiolarian assemblages have so far been recognized (Noble & Danelian, 2004; Maletz, 2007; Noble & Webby, 2009; Danelian et al, 2013). This assemblage was initially considered as Floian in age, but later it was recovered from the lower Darriwilian of Argentina (Maletz et al, 2009) and was considered as covering the upper Dapingian–lower Darriwilian interval (Maletz 2007, 2011)

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