An enigmatic actinopterygian (Pisces: Osteichthyes) from the Upper Permian of China

A new actinopterygian fish Yaomoshania minutosquama gen. & sp. nov., from the Upper Permian of the Dzungaria [Junggar] Basin in China is described. The material consists of two very fragmentary specimens showing almost exclusively scale rows. The arrangement of the scale rows of the holotype resembles the reversion lines of acanthodian caudal fins and of cheirolepids. The size and shape of the scales, and the diminishing size of the scales along the rows, is similar to those of acanthodians and those actinopterygians with small scales such as Cheirolepis. However, the histology of the scales demonstrates features that are found in more advanced actinopterygians: superimposed ganoine lamellae, the arrangement of dentine tubules and pulp canals, buried odontodes stacked on each other to make the ornamental ridges, and an asymmetric pattern of growth achieved by extensive remodelling (resorption and redeposition) of all layers of the scale. Yaomoshania minutosquama is proposed as a small-scale bearing, basal actinopterygian, different from Cheirolepis , but characterized by advanced histological characters.