Fig. 1

a, Schematics showing human outer-ear connective-tissue components derived from the first (red) and second (yellow) arch CNCCs. b, Carnegie stage (CS) human embryos show the fusion of the six hillocks of His (numbered) to form the outer ear (black arrow)48. c, Schematics showing the zebrafish pseudobranch (red) and gill filaments (blue) derived from the first and posterior (blue) pharyngeal-arch CNCCs, respectively. d, Haematoxylin and eosin-stained sections showing the fusion of five filaments at 17?d.p.f. into the pseudobranch (black arrows) at 90 d.p.f. (ref. 49). e?h, Miller?s stain reveals elastin (purple) in cartilage of the adult mouse outer ear (e) and various adult fish gills, including zebrafish (f, left), Atlantic salmon (g), gar, bowfin and bichir (h), but not in zebrafish jaw cartilage (f, right). Scale bars, 50?µm. See the Methods Statistics and reproducibility section for sample sizes. Credits: a and c, created by M.T. in BioRender (a, https://BioRender.com/n31b139 and https://BioRender.com/t64n385; c, https://BioRender.com/x90a752 and https://BioRender.com/a29d934); Carnegie embryos 6521 and 4570 in b were reproduced with permission from the National Museum of Health and Medicine48; the images in d were reproduced with permission from Keith Cheng, Jean Copper and Daniel Vanselow (http://bio-atlas.psu.edu/zf)49.