The effect of jaw curvature on composite crushing performance: how do stingrays eat shells?

Abstract

Durophagous animals are equipped with myriad morphological adaptations for consuming durable prey. Convergent traits for processing hard prey generally include robust feeding musculature, cyclical loading patterns for crushing biological composites, reinforced skeletons, and an array of specialized tooth designs (Van Valkenburgh 1988; Summers, 2000; Summers et al., 2003; Huber et al., 2005). Molariform teeth are well-known in mammals, but cusped and even concave tooth shapes are present in durophagous taxa (Erickson et al. 2012; Crofts and Summers, 2014). In some durophagous stingrays (Family Myliobatidae), the teeth are fused, forming paired (upper and lower jaw) occlusal surfaces. Individual teeth interlock to form this tooth module. As in other elasmobranchs, teeth in these rays are conveyed anteriorly (or labially) as they wear and are eventually shed (Reif et al., 1978). These myliobatid stingrays include the eagle (Aetobatinae), bat (Myliobatinae), cownose (Rhinopterinae), and devil (Mobulinae) rays (Aschliman et al., 2012; Aschliman, 2014). These rays generally prey on bivalves, gastropods, and crustaceans while planktivory in mobulines is considered a derived trait (Ajemian & Powers, 2012; Ajemian et al. 2012; Adnet et al., 2012; Aschliman, 2014).