Fig. 2

RDF variations in rachis apices and cross-sectional profiles. a close-up of one of the two feather apices in DIP-V-16186, with tapered rachis leading to just rachidial ridge (arrowhead); b apex of DIP-V-17109 with broad rachis extending to the end of the vanes (arrowhead); c close-up of the tip of DIP-V-15125, with twisted rachis (arrowhead); d oblique dorsal cross-sectional view of rachis in DIP-V-16202 exhibiting an expansion on the edges (left and right arrowheads) and thin rachidial ridge (center arrowhead), with barbs attaching to rachis laterally (arrows); e cross-section of the rachis of DIP-V-16208; f SEM image of DIP-V-16207, corresponding to e; g DIP-V-17109 oblique ventral view of rachis cross-section in one of the two feathers; h DIP-V-17127 rachis cross-section in oblique lateral view, with rami originating slightly below (left) and exactly on the edge (right), plus thin rachidial ridge. Arrows/arrowheads denote same structures in (d–h). Scale bars = 2 mm in (a); 0.25 mm in (b, d, g and h); 0.05 mm in (c); 0.1 mm in (e and f)