Micro-XRF chemical elementary analysis on the holotype of Sinopterus atavismus Lü, Teng, Sun, Shen, Li, Gao, Liu, 2016 (Pterodactyloidea, Tapejaridae)

The Early Cretaceous pterosaur Sinopterus atavismus, from Northeast China, belongs to the Tapejaridae. The furrowed structure of its wing phalanges is relatively primitive, possibly indicative of atavism. New information of Sinopterus atavismus is therefore of great interest in studies of evolution among Tapejaridae, especially for interpreting some anatomical features of the holotype. In this paper, the distribution patterns and characteristics of chemical elements in the holotype specimen were analyzed by non-destructive micro-X-ray fluorescence (micro-XRF). The chemical mapping results show that the element Ca was significantly associated with pterosaur bones, showing residual traces of the left lower part of the humerus; Sr replaced Ca and the distribution was uniform, suggesting that phosphate recrystallization occurred in the specimen; Fe is concentrated in the soft tissue parts of the pterosaur fossil, which may be related to pyritization, and Mn appears as the alteration phase of the original iron-rich phase. The elemental migration and sedimentary environment of the fossil require further study. The XRF elemental imaging study of Sinopterus atavismus is helpful for explorations of the development and evolution of Tapejaridae, and also provides more chemical information on the taphonomy of the Jehol Biota.

Key words
pterosaur; μ-XRF; elementary scan; Jehol Biota; China