The cartilaginous skeleton of sharks and rays imposes functional limitations that are not seen in bony fishes. Cartilage is less dense than bone, which helps chondrichthyan (cartilaginous) fishes maintain near neutral buoyancy, but cartilage is also less stiff and strong than bone. Nevertheless, some stingrays routinely use their cartilaginous jaws and pavement-like dentition to crush hard prey, such as snails and mussels1. We have studied the cownose ray, Rhinoptera bonasus, to investigate how cartilaginous jaws can be used to crush hard-shelled prey. The jaws are composed of ‘trabecular cartilage’, a material that is structurally and functionally convergent with the trabecular bone found in osteichthyan (bony) fishes and tetrapods.
