Details will be published in the Oct. 1 issue of the journal Nature. Fla. Stingrays are related to sharks, and members of one group of stingrays feed on hard-shelled prey, according to Summers. In the study, he focused on the cownose ray, an Atlantic coast fish that is known for gathering in huge schools very near shore. While bone and cartilage both offer structure, bone provides more strength. This raises the question of how the cownose manages to eat hard-shelled food using its soft, cartilaginous jaws.
Stingrays accomplish the task in two ways.
First, there is a thin layer of mineralization around the cartilage of their jaws, making the jaw rigid and strong, rather than soft and pliable. The mineralization is actually multiple layers of tiny blocks called tesserae, Summers said, laid down in a tile-like way. Secondly, stingrays develop a network of hollow, supportive struts within their jaws. The struts, which are also comprised of tesserae, are concentrated in the areas where toothplates crush prey, providing strength where it is most needed, Summers said The finding also shows that cartilage in a modern animal can provide strength in a way similar to bone, by laying down a thick outer layer and developing inner struts, Summers said. The finding appears to provide scientists with an evolutionary freeze-frame, according to Summers.