Comitatenses

The comitatenses and later the palatini were the units of the field armies of the late Roman Empire.

Terminology
Comitatenses is the Latin plural of comitatensis, originally the adjective derived from comitatus ('company, party, suite'; in this military context it came to the novel meaning of 'the field army'), itself rooting in Comes ('companion', but hence specific historical meanings, military and civilian).

However, historically it became the accepted (substantivated) name for those Roman imperial troops (legions and auxiliary) which were not merely garrisoned at a limes (fortified border, on the Rhine and Danube in Europe and near Persia and the desert tribes elsewhere) — the limitanei or ripenses, i.e. 'along the shores' — but more mobile line troops; furthermore there were second line troops, named pseudocomitatenses, former limitanei attached to the comitatus; palatini, elite ("palace") units typically assigned to the magister militum; and the scholae palatinae of actual palace guards, usually under the magister officiorum, a senior court official of the Late Empire.

List of comitatenses units
Among the comitatenses units listed by Notitia Dignitatum there are:

under the Western Magister Peditum

 * Undecimani (originally formed from the Legio XI Claudia pia fidelis, Moesia);
 * Secundani Italiciani (originally formed from the Legio II Italica, Africa);
 * Tertiani Italica (originally formed from the Legio III Italica, Illyricum);
 * Tertia Herculea, Illyricum;
 * Secunda Britannica, Gallias;
 * Tertia Iulia Alpina, Italia;
 * Prima Flavia Pacis, Africa;
 * Secunda Flavia Virtutis, Africa;
 * Tertia Flavia Salutis, Africa;
 * Secunda Flavia Constantiniana, Africa Tingitania;
 * Tertioaugustani (Legio III Augusta);

under the Magister Militum per Orientem

 * Quinta Macedonica (Legio V Macedonica);
 * Septima gemina (Legio VII Gemina);
 * Decima gemina (Legio X Gemina);
 * Prima Flavia Constantia;
 * Secunda Flavia Constantia Thebaeorum;
 * Secunda Felix Valentis Thebaeorum;
 * Prima Flavia Theodosiana;

under the Magister Militum per Thracias

 * Prima Maximiana Thebaeorum;
 * Tertia Diocletiana Thebaeorum;
 * Tertiodecimani (Legio XIII Gemina?);
 * Quartodecimani (Legio XIV Gemina Martia Victrix?);
 * Prima Flavia gemina;
 * Secunda Flavia gemina.