Orthrozanclus was a weird spiny halwaxid with two plates of armor on top of its body, and surrounding them were scale-like plates on the bottom. It used its squishy foot to move along rocks.
It had many protective spines surrounding the edge of the body. But this defense didn't work with some monster predators, such as Anomalocaris, because Anomalocaris could crunch right through those spines and get to the soft Orthozanclus inside.
Orthozanclus had so many spines because it was not fast and could not swim to escape from predators like its relative Odontogriphus.