670 J. Paleont., 79(4), 2005, pp. 670–686 Copyright  2005, The Paleontological Society 0022-3360/05/0079-670$03.00 NEW DATA ON THE FOLIOMENA FAUNA (BRACHIOPODA) FROM THE UPPER ORDOVICIAN OF SOUTH CHINA REN-BIN ZHAN AND JISUO JIN Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China, rbzhan@nigpas.ac.cn and Department of Earth Sciences, University of Western Ontario, London, Ontario N6A 5B7, Canada, jjin@uwo.ca ABSTRACT—A newly discovered Late Ordovician (early Ashgill) brachiopod assemblage from the Linhsiang Formation in the middle part of the Yangtze Platform, South China, bridges the paleobiogeographical gap between the early Ashgill Foliomena-bearing asso- ciations known previously from the upper and the lower parts of the Yangtze Platform. Characterized by minute shells in calcareous to siliciclastic mudstones, the fauna contains 13 brachiopod genera, of which two plectambonitoids are new: Hadroskolos and Jing- shanella. Cluster and principal component analyses, based on 29 global occurrences of the Foliomena fauna in Laurentia, Avalonia, Kazakhstan, Baltica, Sardinia, Bohemia, Sibumasu, North China, and South China, revealed broad trends of spatial and temporal faunal differentiation in terms of taxonomic compositions. The analyses demonstrate for the first time that early Foliomena-bearing associations of Caradoc age occupied primarily deepwater (distal shelf) environments with a siliciclastic or calcareous mud substrate. The fauna attained its widest paleogeographical distribution and paleoecological range (midshelf to shelf margin settings) during the early Ashgill. INTRODUCTION T HE FOLIOMENA fauna was widespread in lower Caradoc–middle Ashgill rocks of the South China paleoplate, ranging from relatively shallow-water (equivalent to midshelf) to deepwater (distal shelf) settings (Rong, 1984; Rong and Zhan, 1995, 1996), although, globally, most of the known occurrences were in the deepwater range (Sheehan, 1973; Rong et al., 1999). In this study, the term ‘Foliomena fauna’ refers to a wide range of brachiopod- dominated associations characterized by small- and thin-shelled brachiopods of moderate generic diversity, with such diagnostic taxa as Foliomena Havlı ´c ˇek, 1952, Dedzetina Havlı ´c ˇek, 1950, Christiania Hall and Clarke, 1892, and Cyclospira Hall and Clarke, 1893 (see Harper, 1979; Rong et al., 1999), whereas ‘Fo- liomena-bearing association’ is used for a specific occurrence of such fauna. Harper et al. (1999) provided a preliminary, quantitative anal- ysis of the relationships among different associations of the Fo- liomena fauna using four time slices. In the last few years, more associations have been studied systematically, such as the Zhil- gyzambonites–Foliomena association from the top part of the An- derken Formation (middle Caradoc) of Chu-Ili Range, Kazakhstan (Popov et al., 2002), and the Dedzetina–Leangella association from the Domusnovas Formation (middle Ashgill) of Sardinia, Italy (Villas et al., 2002), one of the youngest occurrences of the Foliomena fauna. In South China, new material of the typical Foliomena fauna has become available recently from two locali- ties, one in the Linhsiang Formation of Hubei Province and the other in the Huangnekang Formation of western Zhejiang Prov- ince, both of early Ashgill age. In their thorough review of the global distribution of Foliom- ena-bearing associations, Rong et al. (1999, p. 413, text-fig. 1; p. 418, text-fig. 6) implied the absence of the Foliomena fauna in lower Ashgill rocks in the Yichang area, central Yangtze Platform (the presence of the fauna in the Linhsiang Formation of Yichang, marked ‘‘F’’ in text-fig. 10, was a typographic error). The Fo- liomena-bearing association, discovered in the Linhsiang Forma- tion by the senior author during field work in 2003, contains all the four key taxa of the Foliomena fauna. Among the 107 spec- imens collected from the upper part of the Linhsiang Formation at Daozimiao of Jingshan, Hubei (Fig. 1), 73 are brachiopods and the rest, trilobites. The brachiopods are characteristically small (usually less than 2 mm in shell width) and diverse (13 genera). Previously reported occurrences of the early Ashgill Foliomena fauna in South China are from either the upper or the lower part of the Yangtze Platform (Rong et al., 1999). The new occurrence in the Linhsiang Formation, which forms the basis of this study, is located in the north-central part of the Yangtze Plat- form (Fig. 2), thus bridging the gap in the paleogeographical distribution of the fauna during the early Ashgill. The Foliomena fauna from the Huangnekang Formation, as initially noted by Cocks and Rong (1988), was known from only two brachiopod genera, Foliomena and Christiania. Dur- ing field work (2003), the present authors collected additional material from the Huangnekang Formation at Wujialong, Jiangshan, western Zhejiang Province; the fauna is more di- verse than was known previously and comprises Anisopleu- rella Cooper, 1956, Leangella O ¨ pik, 1933, and Orbiculoidea d’Orbigny, 1847, in addition to Foliomena and Christiania. In light of the new data available, the main objectives of this study are to 1) provide a systematic description of the Foliomena fauna from Hubei Province and 2) carry out mul- tivariate analyses of the global occurrences of the fauna to detect possible patterns of temporal and spatial differentiation in terms of its taxonomic composition. GEOLOGICAL SETTING In Hubei Province, the outcrop that yielded the early Ashgill Foliomena fauna is located 3 km south of the Jingshan county town (Fig. 1). Paleogeographically, the study area was in the north-central part of the Yangtze Platform during the Ordovician (Fig. 2), which received a continuous succession of sediments from the Tremadoc Nantsinkuan Formation to the Ashgill Wufeng Formation. The Ordovician succession is overlain conformably by the Lower Silurian (Rhuddanian) Lungmachi Formation. Early studies of this continuous section include Ma and Wang (1978) and Jin et al. (1990), although no particular attention was paid to the shelly fauna of the Linhsiang Formation. The Linhsiang Formation was first named by Mu and Sheng (in Yang and Mu, 1954), with the type section at Wulipai, Linx- iang (Linhsiang) County, northern Hunan Province. The forma- tion consists of a 19.3-m-thick sequence of grayish-green, nodular limestone. In subsequent studies, the Linhsiang Formation was divided into two parts (Nanjing Institute of Geology and Palaeon- tology, 1974). The lower part was named the Meijiang Formation, which contains a series of nodular limestones rich in nautiloids. The upper part was redefined as the Linhsiang Formation (sensu stricto), characterized by a 2–3-m-thick unit of argillaceous and nodular limestones, with the common trilobite Nankinolithus Lu, 1957 and the brachiopod Anoptambonites Williams, 1962 (see Rong, 1984).