Bite force in the horned frog (Ceratophrys cranwelli) with implications for extinct giant frogs

A Kristopher Lappin,Susan E Evans,David J Moriarty,Stephanie A R Stoeppler,Marc E H Jones,Sean C Wilcox

doi:10.1038/s41598-017-11968-6

Abstract

Of the nearly 6,800 extant frog species, most have weak jaws that play only a minor role in prey capture. South American horned frogs (Ceratophrys) are a notable exception. Aggressive and able to consume vertebrates their own size, these “hopping heads” use a vice-like grip of their jaws to restrain and immobilize prey. Using a longitudinal experimental design, we quantified the ontogenetic profile of bite-force performance in post-metamorphic Ceratophrys cranwelli. Regression slopes indicate positive allometric scaling of bite force with reference to head and body size, results that concur with scaling patterns across a diversity of taxa, including fish and amniotes (lizards, tuatara, turtles, crocodylians, rodents). Our recovered scaling relationship suggests that exceptionally large individuals of a congener (C. aurita) and extinct giant frogs (Beelzebufo ampinga, Late Cretaceous of Madagascar) probably could bite with forces of 500 to 2200 N, comparable to medium to large-sized mammalian carnivores.

Highlights

The evolution of jaws and their use in prey capture has played a key role in the radiation and evolutionary success of vertebrates[1,2,3,4,5]
Using a longitudinal experimental design, we measured bite-force performance in a sample of eight post-metamorphic individuals to test the hypothesis that, typical of fish and amniotes examined to date, this non-amniote tetrapod exhibits a positive allometric increase in bite force during ontogeny
We found that the average area of the pair of palatal conduits, relative to head width, is comparable among C. cranwelli, other Ceratophrys spp. including the exceptional C. aurita specimen, and Beelzebufo (Fig. 3; Supplementary Table S2)

Summary

Introduction

The evolution of jaws and their use in prey capture has played a key role in the radiation and evolutionary success of vertebrates[1,2,3,4,5]. Ceratophrys frogs possess large and highly adhesive tongues[8], they have strong jaws and, quite atypical of frogs, readily bite The strength of their bite is reflected by their extremely wide and short heads, which contain large jaw-adductor muscles and provide a high mechanical advantage, even at the tips of the jaws. Using their disproportionately large head and the forceful bite it affords, Ceratophrys frogs are capable of capturing and subduing prey that can be large, strong, and/or potentially dangerous (e.g., frogs, lizards, snakes, birds, rodents; ref.[9]). Morphological Variable[2] total length snout-vent length head width snout-vent length jaw length head width head width mandibular width mandibular width head width

Methods

Results

Conclusion