 The fins are small and very thin . The pectoral fins are rounded and lobe @-@ like . The two dorsal fins are positioned about between the pectoral and pelvic fins . Each dorsal fin bears a slightly grooved spine in front ; the second dorsal spine is longer than the first . The anal fin is absent , and the caudal peduncle lacks keels or notches . The upper lobe of the caudal fin is larger than the lower and has a notch in the trailing margin . The skin , excluding on the fins , is densely covered with irregularly arranged , nonoverlapping dermal denticles . Each denticle has a swollen rhombic shape with 10 – 40 facets on the crown . The viper dogfish is black with distinct darker markings on the underside . These markings contain large numbers of tiny light @-@ producing photophores ; more photophores are found sparsely scattered over the rest of the body , as well as in a translucent patch on the upper eyelid . The fins are translucent , and the tip of the caudal fin upper lobe is blackish . The largest known male is 47 cm ( 19 in ) long and weighs 0 @.@ 43 kg ( 0 @.@ 95 lb ) , and the largest female is 54 cm ( 21 in ) long and weighs 0 @.@ 76 kg ( 1 @.@ 7 lb ) . 
