Stegosaurian skin impressions from the Upper Jurassic Shangshaximiao Formation, Zigong, Sichuan, China: A new observation

A skin impression fossil of Gigantspinosaurus sichuanensis was found in the Upper Jurassic Shangshaximiao Formation in Zigong, Sichuan. The fossil, preserved on the dorsal face of the left shoulder, clearly shows scales of Gigantspinosaurus sichuanensis. These scales are generally arranged as a net, and most of them are pentagonal, a few being quadrilateral and hexagonal. The maximum inner radius of most scales range from 5.7 to 9.2 mm. The scales are connected with each other by grooves. Scattered within small scales are a few pentagonal or hexagonal large scales, with each large scale surrounded by 13-14 scales. The surface of the scales is rough with string-like ridges. The stringy ridge on the scales made the surface of the scales uneven and thus may reduce the glare caused by reflected light. Based on the primary burial location and distribution of the scales, the authors believe that the skin impression fossil of Gigantspinosaurus sichuanensis is from the elbow of the forelimb, relevant upper arm and lateral area of the body.