 The viper dogfish feeds primarily on bony fishes , notably lanternfishes in the genera Benthosema and Diaphus , and also takes crustaceans . Its long jaws and slender teeth are adapted for grasping rather than cutting , in contrast to the short jaws and saw @-@ like lower teeth of other dogfish sharks that are suited for excising chunks of meat . Prey is seized by a rapid extension of the jaws and swallowed whole ; the shark can consume fish close to 40 % as long as itself . The viper dogfish is the only dogfish species that lacks a suborbital muscle , which is normally responsible for pulling the jaws forward when biting . Jaw protrusion is instead effected by the hyomandibular bone , which is articulated to the skull in a manner that allows it to swing down and forward . This unique arrangement serves to increase the distance the shark can protrude its jaws , as well as the size of its gape both vertically and horizontally . 
