(a) Overview of dorsal wing surface, with claws (red arrows), and extent of coverts along posterior edge of wing (white arrow), dorsal details in a–e. (b) Pale or white plumage spot at base of alula. (c) Contrasting plumage colours and structure near alular digit and claw. (d) Narrow, flexible barb morphology and paler pigmentation in secondary coverts (near arrow in a). (e) Pigment distribution within blade-shaped barbules of alula. (f) Ventral wing surface (apex of primaries in upper left corner), with flap of feather-bearing skin trailing off the proximal edge of wing in counterclockwise direction (arrow), ventral details in f–l. (g) Primaries, where they were apically truncated by amber polishing (arrow). (h) Secondaries, where they have been curled by resin flows, displaying their flexible barbs, and the mixture of contour feathers and down that protrude through a veil of milky amber towards the middle of the wing surface. (i) Barbule morphology and pigmentation in an isolated flight feather. (j) Mat of white plumulaceous barbs (down) near proximal margin of skin flap, with skin towards bottom of image. (k) Definitive down inserting into skin surface, with calamus (arrow) and small sheath basally. (l) Pennaceous and plumulaceous barbs from contour feathers on the skin flap. Scale bars, 2.5 mm (a,f); 1 mm (b–d,g,h,j); 0.5 mm (e,i,k,l).