Abstract: A new eubrachythoracid arthrodire, Phymosteus liui gen. et sp. nov., is described from the Upper Devonian (Early Famennian) Xiejingshi Formation of Shimen County, Hunan, central China. The specimen under study, a nearly complete nuchal plate, was collected from the upper part of the formation in association with plant fossils , such as Leptophloeum guanzhuangense and Cyclostigma hunanense, by Dr. Gen Baoyin of Institute of Botany, Chinese Academy of Sciences in 1990s. The new form is at the pachyosteomorph level of organization having a large nuchal gap and possibly referred to the Selenosteidae of aspinothoracid arthrodires. It is the first record of the aspinothroacid arthrodires from China , but whether it widens the distribution of the Selenosteidae from Europe and North America to Asia needs further fossil materials.