Arandaspis was about 6 inches long, with a streamlined body covered in rows of knobbly armored scutes. The front of the body and the head were protected by hard plates with openings for the eyes, nostrils and gills. It probably was a filter-feeder.
Arandaspis had no fins; its only method of propulsion was the use of its horizontally flattened tail. As a result, it probably swam in a fashion similar to a modern tadpole.