Early Devonian fish material from Posongchong Formation of Guangnan, Yunnan, China

New findings of early vertebrates, including placoderms, sarcopterygians, and the galeaspids Sanqiaspis rostrata, Macrothyraspis longicornis, Gantarostraspis gengi, Wenshanaspis sp., are described from Posongchong Formation (Pragian, Lower Devonian) in Zhujie, Guangnan County, Wenshan Prefecture, Yunnan, China. The new specimen of Macrothyraspis longicornis exhibits the ventral side of its headshield, revealing a large branchial chamber encompassed by a very narrow ventral rim. The material of Yunnanolepidoidei and Petalichthyida represents the first fossil record of placoderms from Wenshan Prefecture, southwestern Yunnan. These new findings enrich the fish diversity of the Pragian Xujiachong Vertebrate Assemblage and provide additional paleoichthyological data for the biostratigraphic correlation between Posongchong Formation and its coeval strata in southwestern China and northern Vietnam.