Fig.1 Leg feathers in the basal avialan Sapeornis from the Lower Cretaceous Jehol Group . Photograph (A) and drawing (B). (Image by ZHENG Xiaoting)

Fig.2. Leg feathers in the basal avialan Confuciusornis (A, B) and the enantiornithine Cathayornis (C, D) from the Lower Cretaceous Jehol Group . (Image by ZHENG Xiaoting)

Fig.3. Integumentary features of the hindlimb in the basal ornithuromorph Yanornis from the Lower Cretaceous Jehol Group . (A) Photograph of STM9-5. Pedal integument of STM9-5 as seen in the slab (B) and counter slab (C). Femoral and crural feathers of STM9-5 as seen in the slab (D) and counter slab (E). (Image by ZHENG Xiaoting)

Fig.4 An artist's reconstruction of Sapeornis. (Image by LI Rongshan)