In the early Roman Republic period, the parma was the type of shield that was used by the lowest ranking soldiers. At that time, parma simply meant shield and came in a variety of sizes and shapes. During the later times, it's form evolved as a practical defence for the soldier who carried it to battle. Each legion carried a single standard, which was of extreme importance. Thus, the ability of the aquifer, the standard bearer, to defend himself was of immense importance.