Fig. 7

Development of the pectoral fins and girdles of A. burtoni. a, b The pectoral girdles and fins of A. burtoni show the typical teleost anatomy. The girdle consists of two dermal bones, the cleithrum and the post-cleithrum, and two endochondral bones, the scapula and coracoid (indicated S and C in panel b). The pectoral fins consist of proximal radials that articulate via distal radials with the main external fin support, the dermal fin rays. The propterygium (see main text) is present as a separate radial during embryogenesis but is in the adult fused to the scapula. Shown is an Alizarin red/Alcian blue stained pectoral fin/girdle complex of an adult fish. c, d Alcian blue stained sequence of pectoral fin development (see main text for details). The cleithrum is indicated from 84 hpf to 138 hpf. Distal radials appear first at 174 hpf, and are present but not indicated in 180 hpf to 222 hpf. The post-cleithrum, which is only visible through its different contrast, is only indicated in 126 hpf and 192 hpf. Abbreviations: hpf: hours post fertilization; S: scapula; C: coracoid