Chiasmodon Niger, Black Swallower Deep Sea Fish

The black swallower feeds on bony fishes, which are swallowed whole. With its greatly distensible stomach, it is capable of swallowing prey over twice its length and 10 times its mass. Its upper jaws are articulated with the skull at the front via the suspensorium, which allows the jaws to swing down and encompass objects larger than the swallower's head. Theodore Gill speculated that the swallower seizes prey fishes by the tail, and then "walks" its jaws over the prey until it is fully coiled inside the stomach.
Black swallowers have been found to have swallowed fish so large, they could not be digested before decomposition set in, and the resulting release of gases forced the swallower to the ocean surface. This is, in fact, how most known specimens came to be collected. In 2007, a black swallower measuring 19 cm (7.4 in) long was found dead off Grand Cayman. Its stomach contained a snake mackerel (Gempylus serpens) 86 cm (34 in) long, or four times its length.