Jianianhualong tengi is a key taxon for understanding the evolution of pennaceous feathers as well as of troodontid theropods. It is known by only the holotype. which was recovered from the Lower Cretaceous Yixian Formation of western Liaoning. China. In this study, we carried out a large-area micro-X-Ray fluorescence (micro-XRF) analysis of the holotype ofJiortior/ma/ortg lengi via a Brucker M6 Jetstream mobile XRF scanner. The elemental distribution measurements of the specimen show an enrichment of typical bone-associated elements. such as S, P and Ca, which allows to visualize the fossil structure. Additionally, the bones are enriched with several heavier elements. such as Sr, Th, Y and Ce relative to the surrounding rocks. The enrichment is most likely associated to secondary mineralization and the phosphates from the bones. Interestingly, the plumage shape correlates with an enrichment in elements. such as Cu, Ni and Ti, consistent with the findings of a previous study' on Archaeoptetyx using synchrotron imaging. Elemental variations among the skeleton, the unguis and the sheath blade further indicate their possible compositional or ultrastructural differences, providing new biological and taphonomic information on the fossilized keratinous structures. An in-situ and nondestructive micro-XRF analysis is currently the most ideal way to map the chemistry of meter-sized fossils and has so far been mainly restricted to small samples. Micro-spatial chemical analysis of larger samples usually required a synchrotron facility. Our study demonstrated that a laboratory-based large-area micro-XRF scanner can provide a practical tool for the study of large specimens, thus allowing to collect full chemical data in order to obtain a better understanding of evolutionary and taphonomic processes.