Diversification patterns of Early and Mid Ordovician graptolites in South China

Abstract

During the Early and Mid Ordovician, graptoloids underwent a dramatic diversification. Many clades (e.g. anisograptids, dichograptids and biserials) originated and subsequently diversified during this interval, playing the most important roles in the evolution history of graptolites. In this study we conduct an analysis of the generic and species diversity history of Early to Mid Ordovician graptolites from the Yangtze Region (platform) and Jiangnan Region (slope) of South China, and provide evidence that the regionally distinct biodiversification patterns are related to the different representative environments of each region.Graptolite diversity measured across graptolite zones displays a remarkable increase in both regions during the Early to Mid Ordovician, but with distinct scales and patterns in each region. In the Upper Yangtze Region, the diversification is less rapid and can be divided into four phases. The second major diversification phase (early Arenig) is characterized by the rapid expansion of dichograptids, and the fourth diversification phase (mid‐late Darriwilian), which is preceded by a decline (third phase), is typified by the flourishing of biserial graptolites. The diversification of graptolites in the Jiangnan Region is more dramatic and shows a distinct pattern of rapid, progressive and sustained diversity rise from the early Arenig to the early Darriwilian. This rapid diversification is initially driven by the expansion of dichograptids and subsequently enhanced by the significant addition of glossograptids and diplograptids.A comparison of diversity patterns between the Upper Yangtze Region, the Jiangnan Region, Australasia, Baltoscandia and Avalonia indicates: (1) the global Arenig expansion of dichograptids is also recorded in South China, (2) the diversity pattern of the Upper Yangtze Region is largely comparable to that of Baltoscandia and Avalonia, but is considerably different from that of Australasia, and (3) the sustained rapid increase of graptolite diversity in the Jiangnan Region is not shared by any of the other regions. Copyright © 2007 John Wiley & Sons, Ltd.

Reconstruction of the Yangtze Ramp during Floian to Darriwilian (Ordovician) in South China: Its Morphology, Controlling Factors and Significances

“…This is shown in microfossil assemblages from this region, such as chitinozoans (Liang and Tang, 2016), acritarchs (Yan et al, 2011), conodonts (Wu et al, 2012). Interestingly, the diversity of graptolites was high but more diversified in the Jiangnan region (Zhang et al, 2007). During late Fl1 to early Fl2, sea-level rose and the rimmed shelf changed to mixed sedimentation ramp along with sufficient supply of terrigenous materials (Luan et al, 2017).…”

“…Spatiotemporally diachronous radiations in clades and data biases characterize the GOBE and continuously hinder our understandings (Servais and Harper, 2018;Harper et al, 2021;Servais et al, 2021Servais et al, , 2023. As a potential cradle for radiation (Harper et al, 2013;Stigall et al, 2019), the GOBE in South China was well-developed during the Early-Middle Ordovician (Zhan et al, 2010;Deng et al, 2021), as shown by the early biodiversification of several clades during this interval (Zhan et al, 2005;Zhang et al, 2007;Liang et al, 2018).…”

Chitinozoan biostratigraphy of the regional Arenig Series in Wales and correlation with the global Lower–Middle Ordovician series and stages

“…The species’ highest occurrence there is in the Acrograptus filiformis graptolite Biozone of the Yangtze Platform (Liang et al . 2018), which correlates with a level in the middle Floian, either in the upper part of Stage Slice Fl1 (Zhang et al 2007, 2010; Wang et al . 2013) or in Fl2 (Zhang et al .…”

“…Dapingian) and lower Darriwilian Stage, and as ranging from the Azygograptus suecicus graptolite Biozone to the Undulograptus austrodentatus graptolite Biozone. As the suecicus Biozone spans the Floian-Dapingian boundary in South China (Zhang et al 2007(Zhang et al , 2010, it follows that the lowest occurrence of Bursachitina laminaris there is likely to be close to the base of the Dapingian Stage (Fig. 7).…”

New insights into the paleobiogeography of the Early Ordovician graptolite fauna of northwestern Argentina

“…In addition, all confirmed Early Floian graptolite records previously mentioned from the Northwest of Argentina (Toro and Brussa, 2003;Albanesi et al, 2008;Brussa et al, 2008) have been incorporated (presence-absence matrix available upon request to the authors). A comparison was made with those faunal associations recently reviewed from equivalent stratigraphic levels of Baltoscandia (Egenhoff and Maletz, 2007), Great Britain (Zalasiewicz et al, 2009), North America (Jackson and Lenz, 2006;Williams and Stevens, 1988) and Southwest China (Zhang et al, 2007).…”