Burgess Shale–type fossil Lagerstätten provide the best evidence for deciphering the biotic patterns and magnitude of the Cambrian explosion. Here, we report a Lagerstätte from South China, the Qingjiang biota (~518 million years old), which is dominated by soft-bodied taxa from a distal shelf setting. The Qingjiang biota is distinguished by pristine carbonaceous preservation of labile organic features, a very high proportion of new taxa (~53%), and preliminary taxonomic diversity that suggests it could rival the Chengjiang and Burgess Shale biotas. Defining aspects of the Qingjiang biota include a high abundance of cnidarians, including both medusoid and polypoid forms; new taxa resembling extant kinorhynchs; and abundant larval or juvenile forms. This distinctive composition holds promise for providing insights into the evolution of Cambrian ecosystems across environmental gradients.

No abstract

A detailed exploration of growth and trunk segmentation of the oryctocephalid trilobite, Duyunaspis duyunensis Chang & Chien in Zhou et al. 1977, from the lower Cambrian (Stage 4, Series 2) Balang Formation in western Hunan Province, South China, is presented. Because of the excellent preservation, the complete post‐protaspid ontogenetic series from merapsid degree 0 to the holaspid phase is described. The ontogenetic series reveals new information on morphological changes such as the migration of the posterior branch of the facial sutures (from proparian to opisthoparian) and contraction of the posteromedial notch in the pygidium. The abundance of articulated specimens available from a narrow stratigraphical interval makes this material singularly useful for studying the morphogenesis and post‐embryonic growth of D. duyunensis in comparison with other oryctocephalids. Strong evidence that multiple numbers of pygidial segment are recognized in each meraspid degree as well as in the holaspid period showed unusual intraspecific variability in the rate of trunk segmentation, providing insights into how Cambrian subisopygous trilobites controlled their body patterning, including size, shape and trunk segment number in both thorax and caudal plate during growth.

A detailed investigation of the morphology and ontogeny of the redlichioid trilobite Eoredlichia intermediata (Bulletin of the Geological Society of China, 3–4, 1940, 333) from the lower Cambrian Yu'anshan Member of the Heilinpu Formation, in Kunming, Yunnan Province, southwest China, is presented. The new material comprises a relatively complete ontogenetic series ranging from the early meraspid to the holaspid period, which reveals more details on morphological variation such as the appearance of bacculae in some holaspid specimens, contraction and disappearance of fixigenal spines, and macropleural spines of the first and second thoracic segments, which are all documented for the first time and can also be used as developmental markers defining ontogenetic phases. Two distinct morphotypes, possibly an expression of intraspecific variation or sexual dimorphism, are distinguished by the morphology of pleural spines of the second thoracic segment in meraspid degree 14 and holaspides. The trunk segmentation schedule of E. intermediata is also discussed and conforms to the protarthrous developmental mode. The distinction of the thoracic region into two portions can be observed during late meraspid and early holaspid periods, which might be considered as a reference for a better understanding on the relationship of tagmosis and growth segmentation among the Cambrian redlichiid trilobites.

The morphology and ontogeny of the eodiscid trilobite Tsunyidiscus acutus Sun is described on the basis of numerous calcified specimens collected from the Lower Cambrian Shuijingtuo Formation in Yichang and Changyang, Hubei Province, South China. An ontogenetic series is established based on the articulated material including the previously unknown protaspides and meraspides (degrees 0 and 1). The material, revealing some prominent morphological changes such as the number of pygidial axial rings, genal spines retained throughout ontogeny and pygidial pleurae from furrowed to unfurrowed, enables a discussion on the trunk segmentation schedule, indicating that somitogenesis and tagmosis occurred independently during the ontogenetic development of T. acutus. Among these taxa, morphological changes from meraspis to holaspis were described (Cederström et al. 2009; Hu 1971; Jell 1970 Jell , 1975 Shergold 1991; Zhang et al. 1980; Zhang 1989; Zhang and Clarkson 1993), and protaspides were found in the following species: P. ocellata, P. resseri, N. chinlinica, T. longquanensis, C. lobatus and B. spinosus.The discovery of new material provides an opportunity to describe ontogenetic sequence of the eodiscoid trilobite T. acutus from the lower Cambrian of South China. Compared with the ontogeny of T. longquanensis (Zhang and Clarkson 1993), the segmentation schedule of T. acutus is investigated, ascribing its developmental mode of trunk segmentation to the protarthrous development (Hughes et al. 2006). MATERIAL, OCCURRENCE AND TERMINOLOGYEntirely preserved specimens comprising 102 protaspides, two meraspides and 15 holaspides have been collected in black shales from two localities in the lower part of the Shuijingtuo Formation in Yichang and Changyang in the Hubei Province, South China: Wangjiaping, 19 km northwest of Yichang, and Dingjiaping, 5.5 km north-west of Changyang (Text- fig. 1). Additionally, several thousand disarticulated exuviae comprising cranidia ⁄ cephala and pygidia of T. acutus, preserved as external and internal moulds, were obtained. Owing to the secondary diagenetic alteration of many specimens, only unfragmented, well-preserved specimens were investigated, including 76 [Palaeontology, Vol. 54, Part 6, 2011, pp. 1279-1288 ª The Palaeontological Association doi: 10.1111/j.1475-4983.2011.01102.x 1279 disarticulated cranidia ⁄ cephala and 199 pygidia. The specimens described and figured are housed in the collection