Fig. 1

Evolution of the limb muscles on the time-calibrated phylogenetic tree. a Acquisition of paired fins. b Establishment of the limb muscles and brachial plexus. c Loss of aquatic larval stage and regeneration capability. d Evolution of the diaphragm from a shoulder muscle. The stippled areas stand for putative transitional forms separating “grades” in fin/limb muscle evolution. The bar in the bottom shows the timescale of the limb muscle evolution. Sarc Sarcopterygia, Tetr, Tetrapodomorpha