[1] They are active hunters, but generally dwell in protected environments such as under stones.

The group is widely distributed from shallow intertidal waters to hadal trenches.

Deep sea species are characterised by a partial or complete loss of antennae, fewer segments, a reduction in jaws and delicate elytra.

[2][4] The Polynoidae has been shown to be monophyletic,[5] however relationships within the family are unclear and hence the number of valid subfamilies has been repeatedly revised in recent years.

One of the main deep sea subfamilies, the Macellicephalinae has been consistently recovered as paraphyletic,[6] and it has been proposed that ten Polynoid subfamilies could be synonymized with it to create a homogeneous clade characterised by a lack of lateral antennae.