Late Roman Unit Sizes

[Nathan Ross]

a similar (!) ranking scheme with centenarii, ducenarii, senator (+primicerius?) and tribunus.

I still haven't come across any theories as to why the auxilia adopted these ranks, rather than the old legion or auxiliary ones - perhaps to 'synchronise' them with the other new units of the imperial retinue - equites, scholae, etc? I'm not sure if we have any certain evidence for ranks within the palatine and comitatenses legions, but as far as I know they seem to have held onto their old ones, with ordinarii etc.

What happened if a tribe has sent 800 men, another tribe just 350? Was the great unit (800 strong) halved? Or did the Romans always demand the same number of soldiers?

My guess is that the institution of the auxilia was an attempt to regularise these previously rather ad-hoc contingents into into units of a set size and composition.

Perhaps men of different tribal (and Roman!) origin were mingled together in some units, and this is why we have these odd titles like Cornuti or Petulantes, or the names of archaic tribes being used?

Some did have current tribal names - Salii, Heruli, Bucinobantes, etc - which might suggest that those peoples, at least initially, were able to supply more men to fill out the entire units, perhaps?