| 论文摘要 |
Two new species of Huananaspidae(Huananaspidiformes,Galeaspida), Huananaspis cupido sp. nov. and Asiaspis liangi sp. nov.,are described from the lower part of the Nagaoling Formation(Pragian,Early Devonian)in Nanning,Guangxi,China. H. cupido sp. nov. differs from H. wudingensis in smaller headshield,lacking median dorsal spine,and cornual processes extending beyond the posterior margin of the headshield. A. liangi sp. nov. differs from A. expansa in headshield length greater than width,cornual processes extending posterolaterally,serrated posterior margin of cornual processes,and longitudinal oval median dorsal opening. The Nagaoling Formation yields reliable index fossils indicating a Pragian age,thus the Xujiachong vertebrate assemblage yielded from this formation can provide a palaeoichthyological standard for stratigraphic correlations of Early Devonian in South China. New findings of Huananaspis and Asiaspis from the Nagaoling Formation enriches the biodiversity of huananaspids,adds new members to the the Xujiachong vertebrate assemblage,and provides direct fossil evidence for the correlation between the Posongchong Formation in Wuding of Yunnan and the Nagaoling Formation in Nanning of Guangxi. The Xujiachong vertebrate assemblage is the most diversified in the transitional beds between the Lianhuashan and Nagaoling formations,almost containing all genera in adjacent regions,indicating that Naning of Guangxi is one of the centers for galeaspids radiating and dispersing. Fish assemblage displays a similar high level of endemism to that of the vascular plants and brachiopod fauna during the Pragian of Early Devonian,which probably caused by the South China sea,a large semi-closed epicontinental gulf. Because of the effect of a closed sea,fishes show exceptional taxonomic diversity and high levels of endemism,forming an independent biogeographic region known as‘galeaspid-yunnanolepid province’ in South China. |
