Fig. 2

Comparison of innervation patterns of pectoral fin/forelimb muscles according to Fürbringer’s theory. a Squalus (shark, elasmobranch chondrichthyes). b Acipenser (sturgeon, non-teleost actinopterygian). c Latimeria (coelacanth, actinistian sarcopterygian). d Neoceratodus (dipnoan sarcopterygian). e Tetrapods. Red circles indicate positions of the plexus (in Squalus, the anastomosis). Arrows shows spinal nerves joining pectoral fin/forelimb muscle innervations, and their respective innervating portions (muscles) are simplified as paths of arrows, according to Fürbringer [88]. Skeletal elements of the metapterygial axis are colored in blue, and the other (preaxial or postaxial) skeletal elements in gray. pl.br, plexus brachialis, pl.ompt.ant plexus omopterygius anterior, pl.ompt.dist plexus omopterygius distalis, pl.ompt.post plexus omopterygius posterior. a b and d are based on Braus [95]. c is based on Millot and Anthony [102]. Metaptarygial axes are based on Shubin and Alberch [64]