The roughhead grenadier or onion-eye grenadier is the animal with the largest eye-to-head ratio in the world.
The roughhead grenadier or onion-eye grenadier is a species of marine ray-finned fish in the family Macrouridae. It is a deep-water fish found in the Atlantic Ocean. The roughhead grenadier can reach a length of one meter (yard). The head occupies about one-quarter of the total length of the fish, it has a slender body and long tapering tail. There are some bony spiny scutes or scales on the upper side of the head but the lower side is scaleless. The snout is pointed and the smallmouth is set far back on the lower side of the head with a short barbel underneath. There are 3 to 5 rows of sharp teeth in the upper jaw and 1 or 2 rows in the lower jaw.
The eye is large and bulbous, giving the fish its alternative name of onion-eye grenadier. There are two dorsal fins, the front one having 11 to 13 fin rays and the hind one running along the back to the tip of the tail. The anal fin is similarly long and narrow and there is no tailfin. The body is covered in large ridged, spiny scales. The general body color is grey, darker underneath, with dark fins and dark edges to some of the scales.