Wikipedia
An aquilifer was a soldier signifer bearing the eagle standard of a Roman legion. The name derives from the type of standard, aquila meaning " eagle" (which was the universal type used since 106 BC), and fers, related to the Latin word for bringing or carrying. Before that time, the wolf, boar, bull and horse were also used. The eagle standard was the most important possession of the legion and its loss was a terrible disgrace.
The aquila emblem generally had up-raised wings surrounded by a laurel wreath. It was mounted on a narrow trapezoidal base and mounted on a pole that was held aloft.
The aquilifer's position was accordingly one of enormous prestige, and he was ranked immediately below the centurions and above the optiones, receiving twice the pay of an ordinary legionary (Brunt, 1950). Unlike other standard bearers (such as signifers), the aquilifer probably did not wear an animal skin, instead going bareheaded (no contemporary depiction of an aquilifer shows him with a headdress or helmet). He is depicted as carrying a small circular shield called a parma that could be strapped on if his hands were already full. (Allen, 1908)