Narial closure in toads; which muscles?

Narial closure in frogs never involves intrinsic narial muscles; rather it is effected by action of the M. submentalis, a muscle of the lower jaw. None of more than 40 species of frogs examined showed any strained muscles in the snout, anterior to the eyes. Direct stimulation of all the relevant muscles, as well as electromyography with simultaneous measurement of air flow at the nostrils, confirms Gaupp's hypothesis that the muscular displacement of the M. submentalis is transmitted via bones and cartilages of the snout to close the nares.