Panxia Wang et Berry 2006 is an endemic fossil-genus from the Middle Devonian of Southwest China. It exhibits the diagnostic features (dissected primary xylem and plectostele) of the Class Cladoxylopsida, but cannot be attributed to the currently existing orders Pseudosporochnales and Iridopteridales within the class. Therefore, Panxia is critical to understand the evolution and diversification of Cladoxylopsida. In this study, we document new materials of Panxia from the Middle Devonian Haikou Formation of Qujing City, Yunnan Province, Southwest China, and assigned them to a new fossil-species, Panxia spinosa sp. nov. This species is characterized by helically arranged lateral branches, spines on both main axes and branches, and recurved ultimate tips that show a hook-like morphology. Anatomically, the main axis possesses a highly dissected primary xylem, and each xylem segment shows a protoxylem strand near its tip. Protoxylem tracheids bear helical thickenings and metaxylem tracheids bear bordered pits. The spines and hook-like tips on branches of Panxia spinosa are interpreted as adaptations for mechanical interlocking between branches, facilitating the formation of dense thickets or clusters. Such morphological innovations likely contributed to the development of complex vegetation structures in the Middle Devonian plant communities. Our study provides better understanding of the cladoxylopsids.