The Early Cambrian Balang Formation is comprised of mudrock and shale, which was deposited in a shelf environment in the eastern part of Guizhou, south China. The Balang Fauna, which consists of seven phyla, occurs in...The Early Cambrian Balang Formation is comprised of mudrock and shale, which was deposited in a shelf environment in the eastern part of Guizhou, south China. The Balang Fauna, which consists of seven phyla, occurs in the middle and upper parts of the Balang Formation. Arthropods are important constituents of the Balang Fauna and include a great number of trilobites, large bivalved arthropods, and newly-discovered well-preserved bradoriid fossils. The bradoriids present include three genera and four species : Comptaluta inflata (Cheng, 1974) emend Hou et al., 2002; Comptaluta kailiensis sp. nov., and Alutella elongeta sp. nov., Aluta sp. This faunal assemblage in the Balang Formation is distinguished from the Tsunyiella Chang, 1964, Songlinella Yin, 1978 and Kunmingella Hou, 1956 assemblage which occurs in the Niutitang and Mingxinsi formations of the Yangtze Platform in middle region of Guizhou and which is earlier than the Balang Formation in age. However, this assemblage resembles the Comptaluta pik, 1968 assemblage from the Early Cambrian Heilinpu Formation in Wuding County, Yuanan Province and from the Ordian Stage of the Cambrian of Australia. The great abundance of Comptaluta pik, 1968 and overall taxonomic diversity of the Comptaluta pik, 1968 assemblage set it distinctly apart from the Alutella Kobayashi et Kato, 1951 and Aluta Hou, 1956 assemblages of the Balang Formation. Alutella Kobayashi et Kato, 1951 and Aluta Hou, 1956 also occur in the Early Cambrian Niutitang Formation of the Yangtze Platform of Guizhou. Individual Bradoriids from the Balang Formation are characterized by large size (>3 mm). The discovery of new Bradoriid assemblages not only expands the group’s geographical range and assemblage affinities, but also indicates that Bradoriids migrated eastward from shallow-water to deeper-water environments during the Early Cambrian, indicating that they were capable of life in deeper-water, and adaptation to a new ecological setting.展开更多
Based on the well-preserved specimens from the Nanba section in Yiyang,Hunan Province,the definition of the graptolite genus Acrograptus is revised here.The revised Acrograptus is a dichograptid form with stipes subho...Based on the well-preserved specimens from the Nanba section in Yiyang,Hunan Province,the definition of the graptolite genus Acrograptus is revised here.The revised Acrograptus is a dichograptid form with stipes subhorizontal to deeply declined,sicula long and slender;th1 1 budding from the top of the metasicula,proximal development of isograptid type with th1 2 as the dicalycal theca;asymmetric proximal end resulting from the divergence of th1 1 and th1 2 from the sicula at different levels;slender crossing canals composed of extremely slender prothecae of th1 1 and th1 2.According to the revised definition,Acrograptus is assigned to the subfamily Sigmagraptinae of the family Dichograptidae,including six species,i.e.,A.affinis (Nicholson),A.filiformis (Tullberg),A.gracilis (Trnquist),A.nicholsoni (Lapworth),A.pusillus (Tullberg),and A.saukros (Ni).During the Early-Middle Ordovician,these six species were widely distributed in South China,especially in the Upper Yangtze Region as well as the central and eastern Jiangnan Region.This study further indicates that Acrograptus first appeared in a deep-water setting on the Jiangnan Slope in South China during early Floian (Tetragraptus approximatus Biozone),and subsequently expanded into the shallow-water region on the Yangtze Platform due to a remarkable dispersion event in middle Floian (Pendeograptus fruticosus Biozone).It is here indicated that the dispersal of Acrograptus may be directly controlled by the large-scale transgression event occurring in middle Floian.展开更多
基金supported in part by grants from the National Natural Sciences Foundation of China (40762001, 40762018)in part by the Mobile project of Science and Technology of Guizhou Province (Grant No. Gui Ji. 2007-4004)+3 种基金the Governor of Guizhou Province(Gui E. 2006-7)the Key Project of International Cooperation of Guizhou Science and Technology Department (Gui. Co. No. 2008-700110)the State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, CAS), (No. 083107)Paleontological Museum of Shenzhen Xianhu Botanical Garden, and the Major Basic Research Projects of MST of China (2006CB806401)
文摘The Early Cambrian Balang Formation is comprised of mudrock and shale, which was deposited in a shelf environment in the eastern part of Guizhou, south China. The Balang Fauna, which consists of seven phyla, occurs in the middle and upper parts of the Balang Formation. Arthropods are important constituents of the Balang Fauna and include a great number of trilobites, large bivalved arthropods, and newly-discovered well-preserved bradoriid fossils. The bradoriids present include three genera and four species : Comptaluta inflata (Cheng, 1974) emend Hou et al., 2002; Comptaluta kailiensis sp. nov., and Alutella elongeta sp. nov., Aluta sp. This faunal assemblage in the Balang Formation is distinguished from the Tsunyiella Chang, 1964, Songlinella Yin, 1978 and Kunmingella Hou, 1956 assemblage which occurs in the Niutitang and Mingxinsi formations of the Yangtze Platform in middle region of Guizhou and which is earlier than the Balang Formation in age. However, this assemblage resembles the Comptaluta pik, 1968 assemblage from the Early Cambrian Heilinpu Formation in Wuding County, Yuanan Province and from the Ordian Stage of the Cambrian of Australia. The great abundance of Comptaluta pik, 1968 and overall taxonomic diversity of the Comptaluta pik, 1968 assemblage set it distinctly apart from the Alutella Kobayashi et Kato, 1951 and Aluta Hou, 1956 assemblages of the Balang Formation. Alutella Kobayashi et Kato, 1951 and Aluta Hou, 1956 also occur in the Early Cambrian Niutitang Formation of the Yangtze Platform of Guizhou. Individual Bradoriids from the Balang Formation are characterized by large size (>3 mm). The discovery of new Bradoriid assemblages not only expands the group’s geographical range and assemblage affinities, but also indicates that Bradoriids migrated eastward from shallow-water to deeper-water environments during the Early Cambrian, indicating that they were capable of life in deeper-water, and adaptation to a new ecological setting.
基金supported by National Natural ScienceFoundation of China (Grant No. 40972009)
文摘Based on the well-preserved specimens from the Nanba section in Yiyang,Hunan Province,the definition of the graptolite genus Acrograptus is revised here.The revised Acrograptus is a dichograptid form with stipes subhorizontal to deeply declined,sicula long and slender;th1 1 budding from the top of the metasicula,proximal development of isograptid type with th1 2 as the dicalycal theca;asymmetric proximal end resulting from the divergence of th1 1 and th1 2 from the sicula at different levels;slender crossing canals composed of extremely slender prothecae of th1 1 and th1 2.According to the revised definition,Acrograptus is assigned to the subfamily Sigmagraptinae of the family Dichograptidae,including six species,i.e.,A.affinis (Nicholson),A.filiformis (Tullberg),A.gracilis (Trnquist),A.nicholsoni (Lapworth),A.pusillus (Tullberg),and A.saukros (Ni).During the Early-Middle Ordovician,these six species were widely distributed in South China,especially in the Upper Yangtze Region as well as the central and eastern Jiangnan Region.This study further indicates that Acrograptus first appeared in a deep-water setting on the Jiangnan Slope in South China during early Floian (Tetragraptus approximatus Biozone),and subsequently expanded into the shallow-water region on the Yangtze Platform due to a remarkable dispersion event in middle Floian (Pendeograptus fruticosus Biozone).It is here indicated that the dispersal of Acrograptus may be directly controlled by the large-scale transgression event occurring in middle Floian.
