A New Family of Galeaspids (Jawless Stem-Gnathostomata) from the Early Silurian of Chongqing, Southwestern China

• 作者: CHEN Yang GAI Zhikun LI Qiang WANG Jianhua PENG Lijian WEI Guangbiao ZHU Min
• 来源期刊: 地质学报（英文版）
• 年，卷（期）: 2022,（2）
• 所属期刊栏目: ORIGINAL ARTICLES
• 页码范围: 430-439
• 页数: 10页
• 语种: 英文

摘要

A new genus and species of agnathan Eugaleaspidiformes (Galeaspida), Yongdongaspis littoralis gen. et sp. nov., is described from the Llandovery (lower Silurian) Huixingshao Formation at Yongdong Town, Xiushan County, Chongqing, southwestern China. This new Telychian taxon morphologically exhibits some transitional states between Sinogaleaspidae and a cluster of higher eugaleaspidiforms containing Tridensaspidae, Eugaleaspidae, Yunnanogaleaspis, and Nochelaspis, which we term here as the ‘eugaleaspid cluster’. Phylogenetic analysis of an extended character matrix of Galeaspida reveals Yongdongaspis, on which Yongdongaspidae fam. nov. is erected, as the sister taxon of this ‘eugaleaspid cluster’, supported by two synapomorphies, the presence of one median transverse canal, and two lateral transverse canals leaving from the infraorbital canal. As the first fish described from the Llandovery Huixingshao Formation in Chongqing, Yongdongaspis provides new fossil evidence for the subdivision and correlation of the Upper Red Beds in South China.