Feeding mode drives mandibular shape in extant Delphinidae

Delphinidae is the most diverse family within the toothed whale clade, displaying two biosonar modes, different feeding strategies, and diving and habitat adaptations. This work examines the delphinid mandible to determine the association between shape, size and ecological variables in extant species. Geometric morphometric analysis on 95 mandibles belonging to 30 (out of 38) extant species, representatives of all 17 extant genera, was performed in occlusal (or dorsal) and lateral (or labial) view. The results reveal that feeding mode and climate primarily drive mandibular shape in extant species. Biosonar mode is an evolutionary driver in mandibular shape in occlusal view, while diet and maximum prey size play a significant role in size only in both views. By contrast, Diving Ecology, Superficial Temperature and Rostral index do not play a significant role in driving delphinid mandibular shape and size. Delphinidae exhibit fascinating morphological adaptations linked to their feeding strategy, biosonar mode and habitat. This study integrates phylogenetic and 2D geometric morphometric analyses to investigate the adaptive significance of mandible morphological variation in response to ecological pressures in Delphinidae. Our results show: (i) that feeding mode drives the mandible shape and highlights the importance of the precoronoid crest with feeding mechanisms; (ii) while the cranium dictates the mean and minimum prey size available, the mandible acts on the maximum prey size; (iii) biosonar mode drives mandibular occlusal shape, confirming the dual role of the mandible: feeding and hearing; (iv) distantly related species adapted their mandible shape primarily to an Artic and cold climate (brevirostrines) and successively to a warm, temperate and tropical environment (longirostrines)