Fig. 13

Graphic representation of the hypothesized origin and diversification of new functions in anurans. The curves represent the increment in the performance of the new function (y axis) through the time (x axis). a The anuran diet is composed of living prey. With the exception of the pipoids, adult anurans share a feeding mechanism in which tongue protrusion is used to capture prey. Three mechanisms of tongue protrusion have been described—mechanical pulling, inertial elongation and hydrostatic elongation—that make prey capture possible [83]. b In ceratophryids, the mandibular symphysis is fixed and immovable [25]. The absence of a movable joint between the mentomeckelian and dentary precludes bending of the mandibular symphysis, which is critical for tongue protrusion in most anuran taxa [79, 84]. The fangs in the ceratophryids are morphological novelties associated with these changes in the mandibular symphysis. The fangs provide the capacity for capturing and subduing large, active prey as well as serving a role in defense against predators [25, 85]. In Ceratophrys sp., the adhesive performance of the tongue is increased by features of its surface profile and material properties, plus mucus [86]. Thus, in horned frogs, biting and tongue protrusion act synergistically to generate the forces to catch large prey well above their own body weight (megalophagy). c In Lepidobatrachus spp., there are additional modifications from the feeding mechanism of terrestrial ceratophyrids that result from changes in development and the origin of morphological novelties, such as the dorsal dermal hyoid bone. Collectively, these changes seem to facilitate catching and swallowing large prey underwater [81]