sentences:  This shark is distinctive in being the only "Centroscyllium" species with abrupt black markings beneath its head, trunk, and pectoral fins, with a black stripe running from under the caudal peduncle to over the pelvic fins.These markings are in fact concentrations of tiny light-emitting photophores.Unusually, this shark also has photophores along the undersides of its upper eyelids.