First Middle Devonian galeaspid from the Haikou Formation in Yunnan Province
The Early Emsian Event (E’Em Event), the most significant bio-event for Chinese Devonian vertebrates, has significantly impacted on the diversity of galeaspids. The endemic Galeaspida almost became extinct after the Mid-Emsian Event (M’Em Event). Only few galeaspid taxa survived from these events, such as Clarorbis apponomedianus from the Eifelian of Guangxi, South China, and an indeterminate galeaspid from the Frasnian of Ningxia, Northwest China. Here, we report the first Middle Devonian galeaspid, Dongfangaspis sp., from the Haikou Formation in Wuding, Yunnan Province. The new material is more suggestive of the type species of Dongfangaspis, D. major, than Laxaspis and Polybranchiaspis in its suborbicular headshield with small inner cornual process, broad and nearly aequilate ventral rim, and about 45 pairs of branchial fossae. Dongfangaspis bears the largest number of branchial fossae ever recorded in galeaspids, which probably play an important role in Dongfangaspis surviving from the E’Em and M’Em events. The new finding represents the second Middle Devonian fossil record of galeaspids, and extends the chronological range of Dongfangaspis from the Pragian (Early Devonian) to the Eifelian (Middle Devonian).