Polynoidae

Polynoidae is a family of marine Polychaete worms known as "scale worms" due to the scale-like elytra on the dorsal surface. Almost 900 species are currently recognised belonging to 9 subfamilies and 167 genera. 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. They are the most diverse group of polychaetes in terms of genus number and second most diverse in terms of species number which is almost 8% of all segmented worm species. thumb| A scale worm moving along the substrate at a depth of 20m in the Lembeh Strait

==Description== Most Polynoidae species are short and flattened, but can reach as much as 20 cm in length and 10 cm width in Eulagisca gigantea and Eulagisca uschakovi. Individuals are usually covered almost entirely by elytra, which can be shed and regenerated in many species. The elytra of some species are faintly bioluminescent, and leave glowing traces around the mouthparts of their predators, making those predators more likely to be attacked in turn.