The pectoral musculature of the Weka, a flightless New Zealand rail, is almost identical with that of a volant relative, the American coot, even to details of the propatagial complex. Similar observations have been made for other flightless carinates, including ducks and cormorants (Lowe 1928a, 1934, 1935). Ratites, in contrast, have far fewer wing muscles than carinates, and lack a propatagium (Lowe, 1928b; McGowan, 1982). The fact that the loss of flight in carinates is accompanied by such little change in the pectoral musculature, while that of ratites is so radically different, weakens the hypothesis that ratites evolved from carinates through the loss of flight.
An assessment of the relationship between muscles and their bony attachment areas shows how little myological information can be deduced from the surface features of bones. Thus, not even the vaguest of muscle reconstructions could have been attempted by studying the pectoral skeleton of the Weka, and similar findings have been made elsewhere (McGowan, 1979, 1982). This raises serious doubts on the validity of reconstructing the musculature of extinct vertebrates, a matter of much interest to palaeontologists.