-The later emperors, around 250-400 AD, used the draco as a symbol of their cohorts. It consisted of a metal dragon or serpent, sometimes just the head, sometimes the whole body, and sometimes with a cloth wind sock on its end, which would fill up with wind, when carried by cavalrymen as it often was. -The bearer of this standard was called the draconarius. -This is the standard I would most like to see in action, as it was sometimes constructed in such a way as to make a loud whistling noise as the wind blew into it.
The Draco was introduced from the East, probably from the Dacians, present-day Romania, and continued to be used later on in Europe after the Roman empire.