The thornback skate (Raja clavata) is probably one of the commonest skates encountered by divers, being among the most abundant rajids in the northeastern Atlantic and Mediterranean. As with all skates, the body is flattened and disc-shaped, with the pectoral fins broadly expanded and joined to the head and body. The tail is distinctly demarcated from the disc-like body, relatively narrow, and about as long as body length. The upper surface of the disc and tail are covered with numerous thorns, which become thickened with button-like bases (known as bucklers) once the skate is sexually mature, hence the species’ common name. Only the snout and margins of the disc are prickly in young, and the underside is only prickly in large, mature females, which also possess more developed ‘bucklers’ on their back and tail. The colour varies from light brown to grey on the upper surface, variegated with dark and light spots and blotches that camouflage the skate in the dappled light of the sea bed, while the underside is creamy-white.