There are 230 species of mostly deep-sea fish in 15 families within this order. Many of them live in the dark depths of the ocean, so they have special adaptations to survive where little light reaches.

These fish usually have long, slender bodies, large mouths, and sharp teeth to catch prey. Some can even open their jaws wide enough to swallow fish almost as big as themselves.

The Aulopiformes include fish such as lizardfishes and tripodfishes. They move quietly and patiently through the water, waiting to ambush smaller fish and invertebrates. Because many live in the deep sea, some can produce light using special organs called photophores, which help them attract food or communicate.