A new basal antiarch, Silurolepis platydorsalis n. gen. n. sp., represented by a large-sized trunk armor and a disassociated anterior median dorsal plate (AMD), is described from the Ludlow (Silurian) of Qujing, Yunnan, southwestern China. It is characterized by its AMD overlapping the posterior median dorsal plate, broad anterior margin of the AMD, and crest-shaped dorsolateral ridge of the trunk armor.
S. platydorsalis represents the first articulated placoderm fish from the Silurian, and amplifies the range of morphological disparity among early antiarchs. On the basis of the available data, the new form is parsimoniously placed at the most basal position of the Antiarcha. It differs from the other antiarchs including yunnanolepiforms in its unique overlap relationship between the AMD and PMD plates, and should represent a newfamily of antiarchs (Silurolepidae n. fam.).
