A new species ofSiyingia from the Lower Devonian Xishancun Formation of Qujing, Yunnan
SI Chu-Dong, GAI Zhi-Kun, ZHAO Wen-Jin
Abstract This paper describes a new species of the Polybranchiaspiformes (Agnatha: Galeaspida), Siyingia perlatuspinosa sp. nov., from the Early Devonian Xishancun Formation in Qujing, East Yunnan, southwestern China. The diagnosis of the genus Siyingia is emended based on data from the holotype of the new species. A phylogenetic analysis, using an expanded version of the data matrix of Zhu and Gai defined in 2006, suggests that Siyingia and Polybranchiaspis form the monophyletic sister group of a clade containing Laxaspis and Damaspis. This discovery increases the known Early Devonian diversity of polybranchiaspiforms, and helps to clarify the pattern of interrelationships within the Polybranchiaspiformes.
Key words Qujing, Yunnan, China; Early Devonian; Xishancun Formation; Polybranchiaspiformes, Siyingia