A new Cathaysiorthis (Brachiopoda) fauna from the lower Llandovery of eastern Qinling, China

Abstract

Following the end Ordovician mass extinction, brachiopod faunas were commonly of low diversity, generally rare in abundance, and restricted to shallow‐water environments in many places. The Cathaysiorthis fauna, first described from South East China, is the most diverse brachiopod fauna in the world succeeding the Hirnantia fauna, and has modified our previous views on the recovery of shelly benthos after the extinctions. Here, we report a newly‐discovered fauna with abundant Cathaysiorthis from the lower Zhangwan Formation (lower–middle Rhuddanian, lower Llandovery) in Qinling, Xichuan County, Henan Province, China. This fauna is slightly younger than that previously documented from South East China, and the evolution of Cathaysiorthis fauna, in terms of its composition, is discussed. The Qinling Cathaysiorthis fauna has a narrower bathymetric range (Benthic Assemblage Zone 3) than that of the fauna from South East China (BA 2–5) and occurred on the Qinling–Dabie Microplate located on the northwest margin of the South China Plate. The migration of the Cathaysiorthis fauna from the South China plate to Qinling–Dabie was achieved by larvae that used ambient ocean currents and possibly drifted from the Jiangnan Region of South East China to Qinling. The Qinling Cathaysiorthis fauna includes 13 species belonging to 12 genera. Two new species, Cathaysiorthis xichuanensis sp. nov. and Aegiria apta sp. nov. are established and described herein, and ten other species are discussed.

The latest Ordovician Hirnantian brachiopod faunas: New global insights

“…23). For the great majority, the Fauna ranges from late Hirnantian to Rhuddanian (Huang et al, 2019), in good agreement with the substantial rise in temperature and sea-level. Our analysis suggests that the post-glaciation faunas may have also occurred in deeper water regimes (BA 4−5, even BA 6) (Rong et al, 2008a;Baarli, 2019;Botting et al, 2019) in the late Hirnantian, when global anoxic conditions (black graptolitic shale) spread out across many places in the world, and shelly benthic faunas are extremely rare.…”

The smooth, spire-bearing brachiopods after the terminal Ordovician extinction through lower Llandovery in the central Oslo region, Norway

“…Moreover, the prevalence of atrypides in the lowest Solvik Formation of the central Oslo region points to early rapid evolution of atrypides there. In contrast, the Rhuddanian Cathaysiorthis fauna from Qinling in southeast China occurs in a range of depth gradients similar to those in the central Oslo area, but harbors only two atrypides, Protatrypa and Lissatrypa , which make up just 3.5% in the fauna (Huang et al, 2019). This might indicate that the Oslo region and nearby terranes in the Iapetus Ocean were a refuge, and later a nexus for the evolution of atrypides at the end of Hirnantian into Rhuddanian times.…”

“…L . hunanensis (Rong et al, 1974), from lower Aeronian in China, which was moved from Thulatrypa to Lissatrypa (Huang et al, 2019), but shares characteristics with both genera.…”