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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.


Holotype GMC V 2416.1 GMC V 2416.2 IVPP V 25445.1
Maximum length of preserved head-shield 76.0 111.0 90.5 92.0
Maximum width of preserved head-shield 72.0 115.0 115.0 101.6
Length of short axis of orbital opening 7.0 6.4 7.2 6.0
Length of long axis of orbital opening 10.0 7.1 7.8 7.6
Distance between orbital openings 24.0 21.0 22.5
Length of short axis of median dorsal opening 11.0 11.0 10.6
Length of long axis of median dorsal opening 20.0 22.5 21.0
Length of short axis of pineal fossa 1.3
Length of long axis of pineal fossa 2.0
Table 1 Measurements of Xiyuaspis zhangi (mm)
Extracts from the Article
Measurements See Table 1.
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