This is the aptly-named "black swallower" (
Chiasmodon niger), a fish known for eating bony fish up to 10x its mass and 2x its length.
It's found worldwide in tropical and subtropical waters at a depth of 700-2,745 meters.
Most specimens of this fish have been collected after one attempted to swallow prey too large for it to handle, and the prey could not be digested before decomposition set it. The release of gases forces the black swallower to the surface.
This particular specimen was found washed up on the shore in 2007. The black swallower measures 19 cm long. The fish in its stomach is a snake mackerel measuring 86 cm.
