Abstract: The Ionoscopiformes are a fossil lineage of halecomorphs known only from the Mesozoic marine deposits. Because of their close relationships with the Amiiformes, the Ionoscopiformes are phylogenetically important in investigating the early evolution and biogeography of the Halecomorphi. However, fossil evidence of early ionoscopiforms was scarce; until recently,Robustichthys from the Middle Triassic Luoping Biota, eastern Yunnan,China, represents the oldest and only known ionoscopiform in the Triassic. Here we report the discovery of a new ionoscopiform, Panxianichthys imparilis gen. et sp. nov., on the basis of two well preserved specimens from the Middle Triassic Panxian Biota, western Guizhou, China. The discovery documents the second ionoscopiform in the Middle Triassic; although Panxianichthys is slightly younger than Robustichthys, it is significantly older than other members of this group from the Late Jurassic of Europe, and Early Cretaceous of North and South America. Panxianichthys possesses an important synapomorphy of the Ionoscopiformes: a sensory canal in the maxilla, but retains some primitive characters unknown in other ionoscopiforms. Results of our phylogenetic analysis recover Panxianichthys as the most primitive ionoscopiform, and provide new insight on the early evolution of this clade. The interrelationships of the Ionoscopidae have been reassessed;Quetzalichthysis regarded more closely related to Ionoscopus than to Oshunia. In addition, our analysis supports the reassessment of Furo muensteri as an ophiopsid ionoscopiform. The successive discoveries of Robustichthys andPanxianichthys from China indicate that the early diversification of the Ionoscopiformes is more rapid than previously thought.