Legionary Officers and NCOs - Late Roman Army (284 - 565 AD)

[Spurius Papirius Cursor]

Again I come hand out for help.

My year 10 elective course ("Sword and Sandal" - we have to have names like that, apparently to excite the kids' imaginations) on the history of the Roman Army develops apace. Albeit, it focuses on the Legions and grinds to a halt about 250 AD.

I gather the late army legions were (more or less) from lowest-to-highest-graded:

limitaneii;
pseudocomitatensis;
comitatensis;
(I think I've forgotten one here);
palatini.

However, regardless of grading, ranks to Centurio remained much the same as under the principate. To me that suggests there would still have been (bottom to top):

Decanus;
Tesserarius; Cornicen; Signifer; Optio; Aquilifer; Vexillarius; Imaginifer;
Centurio
(No, I can't believe this but I can't find anything to replace the structure).

And then??? Well, I imagine with legions from 500 to 1200 men strong (if that) there probably wouldn't have been an elite "First" cohort as in the principate. Were there any top-level centurions?

Going downwards, there's no legate - instead there's a praefect or tribune. No laticlavius or augusticlavii. Who assisted the legion commander in the late army?

Well, that's a few questions I have. Anyone?????

Thanks

SPC