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A reappraisal of the Silurian galeaspids (stem-Gnathostomata) from Tarim Basin, Xinjiang
LIU Yu-Hai, ZHU Min, LIN Xiang-Hong, LU Li-Wu, GAI Zhi-Kun
Vertebrata Palasiatica    2019, 57 (4): 253-273.   DOI: 10.19615/j.cnki.1000-3118.190524
Abstract   (134 HTML6 PDF(pc) (4934KB)(148)  

Some new galeaspid specimens have been recently found from the Silurian of Tarim Basin, Xinjiang. The description of these specimens and the new examination of the galeaspid collections render us the following understanding on the morphology and taxonomy of the Silurian galeaspids from Xinjiang. 1) Nanjiangaspis zhangi is removed from the Hanyangaspidae, and referred to a new genus of the Xiushuiaspidae, Xiyuaspis gen. nov.; 2) Platycaraspis tianshanensis is the junior synonym of Microphymaspis pani. According to the principle of priority, Microphymaspis pani is retained, but it is removed from the Xiushuiaspidae, and referred to the Dayongaspidae; 3) the specimen that was referred to the Arthrodira indet. from the Kezirtag Formation of Kalpin, is identified as a new genus and species of galeaspids, Jiaoyu imperfectus gen. et sp. nov.; 4) the fragments and the anterior ventral plate with snowflake-like ornaments previously referred to Hanyangaspis from the Tataertag and Yimugantawu formations probably belong to Nanjiangaspis; 5) the age of the upper member of the Kezirtag Formation is probably Early Devonian as indicated by Jiaoyu imperfectus and the invertebrate fossils from the lower member.

Fig. 1 Photographs of Xiyuaspis zhangi IVPP V 25445.1-3 and their interpretative drawingA. an incomplete head-shield (V 25445.1): A1, A2. internal mould and its interpretative drawing
(V 25445.1a), A 3. close-up of granulous ornamental tubercles (box region of A 1), A 4, A 5. external mould and its interpretative drawing (V 25445.1b); B. a nearly complete ventral rim (V 25445.2);C. a nearly complete corner (C 1) and its interpretative drawing (C 2) (V 25445.3)
Abbreviations: c. corner 角;ltc a-c. the first to third lateral transverse canals issuing from the infraorbital canal 从眶下管发出的第一至三对侧横管;ltc 1-3. the first to third lateral transverse canals issuing from the lateral dorsal canal 从侧背管发出的第一至三对侧横管;md.o. median dorsal opening 中背孔;orb. orbital opening 眶孔;vr. ventral rim 腹环
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( Figs. 1-3A)
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