Following this requirement, each Roman citizen was enrolled in one of the 35 Roman tribes known since the Republican era. Despite this legal framework, however, already during the time of Gaius Julius Caesar and Octavian Augustus, the tribus Iulia emerged, followed later by Claudia under Claudius—both falling outside the traditional tribal system. These actions by the principes were undoubtedly linked to their intention of broadening the social base of imperial power, a policy that continued under their successors. Thus, new citizens were assigned to the imperial tribes—Fabia under Augustus, Quirina under the Flavian emperors, Papiria under Trajan, and Sergia under Hadrian. In many instances, entire communities (e.g., in Gaul, Sicily, Africa, Baetica, and elsewhere), or military units granted Roman citizenship, were affiliated with these tribes en bloc.

All of this, combined with the loss of voting authority of the tribal comitia under Tiberius and the end of formal ratification of imperial decrees by the people by the time of Domitian, resulted in the gradual obsolescence of the traditional tribes and the abandonment of the existing tribal system. This was a gradual process, culminating during the reign of Hadrian. Newly created Roman citizens could no longer be entered into tribal registries, primarily because such registries ceased to exist.

Indeed, the Roman practice of tribal affiliation persisted sporadically thereafter, but it had become a relic of the Republic’s illustrious past. Tribal designation now served more as a symbol of prestige than as a source of actual privilege. Nevertheless, the tribal affiliation did not disappear from the official nomenclature of Roman citizens. A new mechanism had to be devised to replace the now-defunct traditional system.

Thus emerged the so-called pseudo-tribe, primarily observable among those Romans who acquired citizenship through successful completion of military service and honorable discharge (honesta missio) under the principes. According to numerous known epigraphic monuments, the basis for these new tribal designations was the epithet of the relevant civitas, presented as the origo, and reflected in the official title. This epithet corresponded to the gentilicium of the emperor who had elevated the civitas to its status—e.g., Iulia, Augusta, Flavia, Ulpia, Aelia, Aurelia, Septimia. In this way, the so-called pseudo-tribes—designated as such by G. Forni—resemble the practice established under the Julio-Claudian dynasty. Unsurprisingly, in some scholarly works these new tribes are referred to as “imperial.” There are also rare instances, such as an inscription from Drobeta, where the emperor’s cognomen was used instead.

This solution to the issue, however, could only be applied to those citizens originating from Roman colonies and municipia. It is well known that in such cases, elevation to civic status was typically marked by the adoption of the emperor’s gentilicium—the one responsible for granting the new status—as part of the city’s official name. In a significant number of cities across the empire, however, this rule could not be fully applied, as they did not possess the corresponding status of a Roman city. These include the numerous peregrine cities (civitates stipendiariae) across the empire, especially prevalent in the eastern provinces, such as the cities of Thrace, many of which lacked any such imperial epithet in their names.

While prior to 193 CE this problem remained largely unnoticed—since tribal affiliation was typically not recorded in the nomenclature of auxiliary veterans, particularly Thracians, as shown for instance in the military diploma of C. Iulius C. f. Valens, Tralli (dated 19 July 114 CE) (RMD I, no. 14)—the situation was different for the Praetorian Guard. As the elite corps of the empire, both militarily and socially, the use of a pseudo-tribe in their official nomenclature was mandatory. With the integration of Thracians into the Praetorian Guard, the question of how to assign their pseudo-tribe became pressing.

Those Praetorians whose origo was a city bearing an imperial gentilicium as an epithet in its official title—for example, Nicopolis ad Istrum—unquestionably adopted that epithet, in this case Ulpia. However, Ulpia Nicopolis ad Istrum is more the exception than the norm. The official titles of most other cities lacked such an epithet, leading to the emergence of diverse pseudo-tribes used by Thracian Praetorians.

Numerous preserved laterculi praetorianorum, inscribed in Rome during the last decade of the second and the first third of the third century CE, attest to the use of Claudia, Flavia, Ulpia, Aelia, and Iulia. The majority of veterans favored Trajan’s gentilicium, prompting Bulgarian scholarship to define the so-called “Ulpian” cities, whose foundation and elevation to urban status are linked with Trajan’s program of urbanization in Thrace. Among these cities are Pautalia, Serdica, Anchialos, Hadrianopolis, Philippopolis, Marcianopolis, Bizye, Nicopolis ad Nestum, Perinthus, and others.

Notably, only six of these—Pautalia, Serdica, Nicopolis ad Nestum, Anchialos, Topiros, and Nicopolis ad Istrum—feature Ulpia in their official inscriptions or local coinage, raising doubts about the validity of this thesis. Skepticism deepens when considering cities whose veterans exhibit multiple imperial gentilicia beyond Ulpia. Examples include: Pautalia (Ulpia and Aelia), Philippopolis (Ulpia and Flavia), Serdica (Claudia, Aelia, and Ulpia), Bizye (Iulia and Ulpia), and even the colony Claudia Aprensis with the pseudo-tribe Ulpia. It appears that the use of Ulpia may need to be explained by a different factor, more likely related to the elevation of the province of Thrace between 110 and 112 CE, when the former administrative head—the procurator Augusti—was replaced by a legatus Augusti pro praetore (Thomasson 2011: 22:010). This change enabled the subsequent urbanization of Thrace, accompanied by administrative reforms. It is this reform that is considered the likely reason for the use of Ulpia in the laterculi praetorianorum of Thracian veterans (Galsterer-Kröll 1972: 54).

Moreover, it is possible that the widespread use of Ulpia, evident not only in the nomenclature of Thracian veterans in Rome at the end of the 2nd and the beginning of the 3rd century CE, was also a consequence of the popularity that Trajan’s gentilicium had acquired during this period. This popularity may be attributed to the successful Parthian campaign of Septimius Severus, who deliberately followed in the footsteps and emulated the actions of the Optimus Princeps—Trajan—undertaken several decades earlier.

The inscriptions also reveal additional factors underlying the selection of a pseudo-tribe, some of which represent individual or exceptional cases. One such example is the laterculus CIL VI, 32624, which records: T(itus) Ae(lius) T(iti) f(ilius) Ael(ia) Titianus Pauta(lia). This, along with similar inscriptions, demonstrates the close relationship between the pseudo-tribe and the imperial gentilicium adopted within the veteran’s formal name. In this instance, the praenomen and nomen suggest a military milleu for Titianus, as his predecessor—after whom he was named—had received Roman citizenship and a Roman name upon honorable discharge from service in the equites singulares Augusti. Through the choice of pseudo-tribe, his descendant paid tribute to the emperor who had integrated his family into the Pax Romana, along with all its accompanying privileges.

This example is not isolated; consider also [C.?] [-I]ulius C. f. Iul. Maximus Bize (CIL VI 32640, 31), which reflects a similar pattern.

Another variant is represented by the laterculi listing Praetorians from Thrace whose origo is identified as Philippopolis. It is well established that during the last quarter of the 1st century CE, veterans from the tribe Quirina were settled in the city and its surrounding territory, and a significant portion of the local elite was also affiliated with this tribe. It is likely that their descendants appear in the laterculi from Rome dating to the early 3rd century, such as [M.] Aurel(ius) M. f. Qui(rina) Orestes, Trim(ontium) and T(itus) Fl(avius) T(iti) f(ilius) Qui(rina) [An]tiochus IRIMU, assuming IRIMU can be reconstructed as Trimu(ntium) (sic!) (CIL VI 32640).

It seems, however, that affiliation with the Quirina tribe came to signify noble origin for its bearers by the late 2nd to early 3rd century CE, given that a substantial number of veteran Praetorians from Philippopolis instead used the pseudo-tribe Flavia in the laterculi recorded in Rome.

The solutions presented here do not exhaust the complexities surrounding the mechanisms of pseudo-tribe selection in the nomenclature—not only of Thracian veterans, but more broadly as well. Nonetheless, they offer a unique perspective into Roman society, allowing to glimpse aspects that have thus far remained relatively obscure. In particular, they illuminate certain features of the imperial patronage system—specifically the relationship between the emperor and his “children,” the veterans, whose loyalty and support he could consistently rely upon during times of political difficulty.