How does the toad flip its tongue? Test of two hypotheses.

Two conflicting hypotheses purport to explain the mechanism generating the lingual flip in frogs. The first suggests that the intrinsic tongue muscles are stiffened, rotate over the symphysis and catapult the soft tissues; the second suggests that the hyoid suddenly moves forward and transfers its momentum to propel the tongue. High-speed cinematography and synchronized electromyography show that the tongue is rotated over the symphysis by a complex of rods formed from stiffened intrinsic tongue muscles. As the flip occurs even when the hyoid is immobilized, the hyoid momentum hypothesis does not apply. The tongue is then propelled by sets of fibers locked into connective tissues. With activation, these become rigid rods that form a muscular ballista.