Abstract Monitor lizards (Varanidae) comprise 88 species exhibiting morphological and ecological diversity. Because diet and habitat impose functional constraints on cranial morphology and bite force, we investigated their evolutionary relationships using phylogenetically informed comparative methods. Body size strongly influenced cranial morphology, initially masking ecological signals. After correcting for size, clear patterns of size-independent cranial shape variation emerged. Insectivorous, arboreal, and saxicolous species exhibited proportionally more elongated heads, consistent with trade-offs favouring jaw closing speed over force, whereas durophagous species showed taller, more robust heads adapted for forceful biting. Comparative analyses indicated that habitat and diet primarily influence head shape rather than size, with habitat effects driven mainly by terrestrial–arboreal contrasts and dietary effects by divergence between durophagous and insectivorous species. Morphological disparity analyses revealed that habitat use structures head shape diversity once size effects are removed, whereas dietary categories show comparable variation. Varanus komodoensis consistently occupied an isolated position in morphospace. Terrestrial and carnivorous species exhibited higher bite forces than arboreal, saxicolous, and insectivorous species, but differences disappeared after accounting for body size. Lower jaw length was the strongest predictor of bite force. Finally, we estimated bite force in the extinct varanid Megalania (Varanus priscus) and compare it to data for other large predators.
Rouault et al. (Thu,) studied this question.