The adult queen foot worm can reach 19~37 cm in length. Such a huge size is rare in deep-sea animals, and other isopods are only 1-5 cm. In fact, people should be familiar with animals of this size. For example, we can often see the terrestrial cousin of the king with a foot worm-forest lice. They all have flat bellies and backs, and they all have hard scaly calcareous external bones. In this way, the scales are integrated with the head, bottom and tail, just like a shield with a tail and a short abdomen.

The queen foot worm has a compound eye, which consists of nearly 4000 small flat eyes. Stapless compound eyes keep a distance from each other at the head. In addition, the king has two pairs of tentacles.

The king's biped has seven pairs of articulated legs, and the first pair of articulated legs evolved into jaw feet, so that food can be sent to four sets of jaws. There are five scales called pleonites in the abdomen, and each scale has a pair of two-legged ventral feet for moving in the water. The flat branches with respiratory structure play the role of gills.