Romulan Rank
From Star Trek : Freedom's Wiki
The Romulan Rank System is less scaled than the Starfleet Rank system. e.g, they have no Sub Admiral's, (Commodore, Vice, Rear, and Admiral) as in the Starfleet Rank system. Any Officer who reaches the Rank of Admiral in the Romulan Empire is give the task of commanding a Military area of the Romulan Star Empire, and is the leading military officer in that region. Similarly, the Romulans have no rank of Lt. Cdr this is because Centurions are the backbone of the Romulan Fleet and only the lucky individual's who have proven there leadership and command skills are promoted to Sub-Cdr, with no intermittent stage in between as in Starfleet..