from the proconsuls of Africa Proconsularis and Asia through those governed by consulares and correctores to the praesides. The provinces in turn were grouped into (originally twelve) dioceses, headed usually by a vicarius, who oversaw their affairs. Only the proconsuls and the urban prefect of Rome (and later Constantinople) were exempt from this, and were directly subordinated to the tetrarchs. Although the Caesars were soon eliminated from the picture, the four administrative resorts were restored in 318 by Emperor Constantine I, in the form of praetorian prefectures, whose holders generally rotated frequently, as in the usual magistracies but without a colleague. Constantine also created a new capital, named after him as Constantinople, which was sometimes called 'New Rome' because it became the permanent seat of the government. In Italy itself, Rome had not been the imperial residence for some time and 286 Diocletian formally moved the seat of government to Mediolanum (modern Milan), while taking up residence himself in Nicomedia. During the 4th century, the administrative structure was modified several times, including repeated experiments with Eastern-Western co-emperors. Detailed information on the arrangements during this period is contained in the Notitia Dignitatum (Record of Offices), a document dating from the early 5th century. Most data is drawn from this authentic imperial source, as the names of the areas governed and titles of the governors are given there. There are however debates about the source of some data recorded in the , and it seems clear that some of its own sources are earlier than others. Some scholars compare this with the list of military territories under the duces, in charge of border garrisons on so-called limites, and the higher ranking , with more mobile forces, and the later, even higher magistri militum. Justinian I made the next great changes in 534–536 by abolishing, in some provinces, the strict separation of civil and military authority that Diocletian had established.This process was continued on a larger scale with the creation of extraordinary Exarchates in the 580s and culminated with the adoption of the military theme system in the 640s, which replaced the older administrative arrangements entirely. Some scholars use the reorganization of the empire into themata in this period as one of the demarcations between the Dominate and the Byzantine (or the Later Roman) period. Primary sources for lists of provinces Early Roman Empire provinces Germania (ca. 100) Geography (Ptolemy) (ca. 140) Late