Fig. 1

Palaeognath syringeal elements with tracheosyringeal cartilages differentiated by brown shading (b-e), interannular tissues are shaded in grey. a-b Cassowary, Casuarius casuarius, FUR180; ventral, scale bar = 10mm. c Tinamou, Nothura darwinii, adapted from Garitano-Zavala ([40], fig. 1C); ventral. d Rhea, Rhea americana, adapted from Forbes ([18], fig. 7, 8); ventral and dorsal. e Kiwi, Apteryx mantelli, adapted from Forbes ([18], fig. 3), ventral. f Ostrich, Struthio camelus, adapted from Forbes ([18], fig. 1); ventral. Abbreviations: bs.cs: bronchosyringeal cartilages, ia.i: interannular interval, tr.c: tracheal cartilages, trs.cs: tracheosyringeal cartilages. c-f scaled to same size approximately