"Cartilaginous" refers to something that is made of or relates to cartilage. Cartilage is a firm, flexible tissue found in the body, especially in areas like the nose, ears, and joints, that provides support and cushioning. Full definition
But if there is no reaction, which was the case when Bronson and Maisey performed the test, it is likely made from calcium phosphate, as are the fossilized skeletons of cartilaginous fish like sharks and rays. (sciencedaily.com)
Although some fossils have also preserved hints of cartilaginous tissue, none have included the braincase or postcranial parts of these fish. (sciencemag.org)
The researchers were forced to conclude that the pup had no father, making it the first documented case of asexual reproduction in cartilaginous fish. (newscientist.com)