An indicator of the onset of the end Ordovician mass extinction in South China the Manosia brachiopod assemblage and its diachronous distribution.
The end Ordovician mass extinctions have been closely related to the formation and melting of Gondwanan ice masses. It is also suggested that the beginning of the extinctions may have been marked by the appearance of the cool-water-adapted Hirnantia brachiopod fauna; but investigation of new brachio...
| Main Authors: | , |
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| Format: | Report |
| Language: | English |
| Published: |
2019
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| Subjects: | |
| Online Access: | http://ir.nigpas.ac.cn/handle/332004/29089 http://ir.nigpas.ac.cn/handle/332004/29090 |
| Summary: | The end Ordovician mass extinctions have been closely related to the formation and melting of Gondwanan ice masses. It is also suggested that the beginning of the extinctions may have been marked by the appearance of the cool-water-adapted Hirnantia brachiopod fauna; but investigation of new brachiopod material from the uppermost Katian and lower Hirnantian strata in the Yangtze Region, South China may modify the latter point of view. In the Yangtze Sea, a microcosm of the global perturbations in the Late Ordovician, there occur mixed-facies strata between the Wufeng Formation (black shale with graptolitic facies) and the Kuanyinchiao Beds (shelly facies with the Hirnantia-Mucronaspis Fauna) in the Upper Yangtze Region and within the Xinkailing Beds in the Lower Yangtze Region. These strata may represent a transitional stage of major changes in depositional environments and provide crucial evidence of the initial impact of the formation of the Gondwanan continental ice sheet on the South China Palaeoplate. However, they have been often neglected due to a thin development of sediments and inadequate research on their faunas. Based on collections accumulated during the last half a century, the present authors describe and revise systematically the genus Manosia Zeng, 1983, an overwhelmingly dominant, opportunistic taxon, associated rarely with the rhynchonellide brachiopods (Thebesia) and the trilobites (Triarthrus) in the mixed-facies strata. Its type species is assessed, concluding that the type species, Manosia yichangensis Zeng, 1983 is synonomised with Oxoplecia? inconstanta Xu et al., 1974 since both are conspecific. In the light of rare, well-preserved specimens with spiralia directed centro-dorsally, it is confirmed that Manosia belongs to the atrypides, and is provisionally assigned to the Family Atrypidae. The basic features of the Manosia Assemblage and its spatial and temporal distributions are discussed. Manosia failed to migrate out from the South China Palaeoplate, which palaeogeographically, may ... |
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