Late Sandbian (Sa2) radiolarians of the Pingliang Formation from the Guanzhuang section, Gansu Province, China

Siyumini Perera,Jonathan C Aitchison

doi:10.1017/jpa.2021.86

Abstract

AbstractA diverse, well-preserved radiolarian assemblage is reported from the Sandbian age Climacograptus bicornis Graptolite Biozone. This new assemblage, recovered from the Pingliang Formation in the Guanzhuang section, China, includes six new species along with 13 other previously described taxa. Geminusphaera new genus incorporates G. grandis n. sp. and G. kongtongensis n. sp. and is proposed for inaniguttids constructed from two distinct porous spheres bearing seven or more primary spines. Protopylentonema new genus is introduced to incorporate pylomate entactinarians with five-rayed initial spicules. It includes P. ordosensis n. sp. as well as P. aperta, P. rimata, and P. insueta that were formerly assigned to Kalimnasphaera. Micro-computed tomography investigation of skeletal microstructure supports establishment of the new genera together with other new spumellarian species: Haplotaeniatum implexa n. sp., Inanigutta quadrispinosa n. sp., and Kalimnasphaera pingliangensis n. sp. It also indicates that family-level reassignment of Etymalbaillella from the Proventocitidae to the Ceratoikiscidae is appropriate.Global distribution of Late Ordovician radiolarian occurrences highlights a strong preference for areas with equatorial to tropical sea surface temperatures. This must have led to ecological stress among radiolarian communities in adapting to global cooling in the Hirnantian.UUID: http://zoobank.org/3d3f55b8-0e70-4f9f-9738-265750d8ec3a.

Highlights

Taxonomic research on early Paleozoic radiolarians from isolated occurrences is progressing rapidly compared to that for biostratigraphic correlation and paleoecological investigations, resulting in an improved understanding of systematics over the past two decades
Radiolarians are the only siliceous biomineralizing zooplankton known to have participated in the GOBE
The gradual or sudden increment of the taxonomic richness experienced by marine organisms, including radiolarians, during Early to Middle Ordovician is recognizable in many diversity studies conducted regardless of the region (Stigall et al, 2019; Danelian and Monnet, 2021)

Summary

Introduction

Taxonomic research on early Paleozoic radiolarians from isolated occurrences is progressing rapidly compared to that for biostratigraphic correlation and paleoecological investigations, resulting in an improved understanding of systematics over the past two decades. Western Newfoundland, where more than a dozen radiolarian studies have been conducted during the last three decades, is one of the most intensively studied areas with numerous Lower and Middle Ordovician localities (Aitchison et al, 1998; Won and Iams, 2002, 2011, 2013, 2015a, b; Won et al, 2005, 2007; Maletz, 2007; Pouille et al, 2014; Kachovich and Aitchison, 2020, 2021). The Guanzhuang section, Pingliang, China, is the most well-known locality for Upper Ordovician (Sandbian) radiolarians. It is stratigraphically well calibrated using abundant graptolites and conodonts in shale and limestone beds and was once a candidate for the Global Boundary Stratotype Section (GSSP) of the base of Upper Ordovician (Sun, 1933; Chen et al, 1984; Finney et al, 1999; Wang et al, 2013).

Methods

Results

Conclusion