Late Roman Army - seniores and iuniores

[Nathan Ross]

the translation of the ND I used was not clear on identifying some units as iuniores or seniores.

Only about half the units listed in the ND are either seniores or iuniores - the other half have only the single name. This, I would think, is further suggestion that the distinction was not the result of a single empire-wide policy but rather of an occasional doubling of certain units, perhaps at various times; either (and I accept the points raised above!) by raising a new unit, perhaps using a cadre of men from the 'senior' formation, or by drawing a new 'junior' draft from the original legion that had provided the 'senior' detachment.

In case of the former I'd expect not 'iuniores' but perhaps 'secundani' etc.

Well, yes - but we already have a unit called Secundani, and another called Primani... that would lead to the Primani Primani, and the Secundani Secundani, which would be arcane even by the standards of Roman nomenclature!