Viperfishes are mostly found in the mesopelagic zone and are characterized by long, needle-like teeth and hinged lower jaws.

Viperfishes are capable of bioluminescence and possess photophores along the ventral side of their body, likely used to camouflage them by blending in with the less than 1% of light that reaches to below 200 meters depth.

[3] Extremely large, fang-like teeth give the fish a slightly protruded lower jaw.

Viperfishes live in meso- and bathypelagic environments and have been found dominating submarine calderas such as the Kurose Hole, which is the site with the highest Chauliodus density known in the world.

[9] In the retina, several rows of rod cell "banks" grow upon each other, increasing in number with size of the fish.

[9] The first dorsal ray of Chauliodus is elongated, hinged, and connected via musculature; allowing it to swing forward.

[3] Chauliodus species utilize their capability of bioluminescence for two distinct purposes: attracting prey and avoiding predators.

[10] Chauliodus possesses a bioluminescent lure located at the tip of its first dorsal ray, which it uses to attract prey by swinging it forward in front of its mouth.

[10] Chauliodus has photophores along the ventral side of its body that emit light through adrenergic nervous control.

[7] Based on the diel vertical migration of its prey, viperfish are assumed to be epipelagic migrants that search surface waters for food.

In migrating to the surface (400m depth) at night, they prove their ability to withstand large temperature changes of up to 7°C daily.

[16] That same study showed a skewed 1:2 sex ratio favoring females in their collection of over seventy Chauliodus sloani viperfishes in the Gulf of Mexico.