Replacements of Major Cephalopod Faunas in Late Cambrian and Ordovician in South China

Evolution of Ordovician cephalopod diversity in the Middle Yangtze region of South China and its controlling factors

“…Regional evolutionary processes were different from those at the global scale: the cephalopods of Laurentia began to radiate steadily during the Darriwilian and reached their peak diversity in the Middle Katian (Kröger 2013); the cephalopods of Baltica had a low diversity in the Early Ordovician and two diversification events occurred in the Dapingian to the Middle Darriwilian and the Middle Katian (Kröger 2013). The diversification of cephalopods in South China began in the Floian with a peak in the Late Floian (Fang et al 2019b). The main contributors to the peak were the orders Ellesmeroceratida, Endoceratida, and Orthoceratida.…”

“…The Sandbian diversity decrease observed for these three orders interrupted the continued high diversity of Middle Ordovician cephalopods in South China, while the composition of the cephalopod fauna changed. With the gradual diversification of Tarphyceratida and Oncoceratida and the recovery of Orthoceratida, a small-scale radiation event occurred in the Early Katian (Fang et al 2019b).…”

“…The stratigraphically earliest records of fossil cephalopods represented by Plectronoceras cambria and a few other species are from the Uppermost Cambrian of North China (Walcott 1905;Kröger and Zhang 2009;Kröger 2013;Fang et al 2019a). After near-extinction at the end of the Cambrian, cephalopods underwent significant diversification and palaeogeographical differentiation during the Ordovician and experienced another extinction period at the end of the Ordovician (Frey et al 2004;Kröger and Zhang 2009;Kröger 2013;Fang et al 2019b). Because almost all cephalopods are passive or active swimmers (Westermann 1998), they were able to extend to almost all marine environments, occupied the top of the Ordovician marine trophic chain and played a central role in the aquatic ecosystem (Kröger and Zhang 2009).…”

“…Therefore, studying cephalopod diversification and its controlling factors is very important for understanding the GOBE and the LOME. However, the evolution of Ordovician cephalopod diversity was less consistent with global-scale extrinsic forces (Kröger and Zhang 2009;Fang et al 2019b). For this reason, it is very important to study the factors controlling cephalopod diversity in specific regions such as the Middle Yangtze region.…”

“…Crick 1993;Frey et al 2004;Kröger and Zhang 2009). Fang et al (2019b) described the evolution of Late Cambrian to Ordovician cephalopods in the South China Plate based on relatively comprehensive outcrop data but did not discuss the controlling factors. In the present study, three stratigraphically complete, fossil-rich sections with supposedly similar palaeoenvironments in the Middle Yangtze region were selected as research objects.…”