Roman portrait of Caligula from the Yale University Art Gallery (YUAG) inv. 1987.70.1. Gaius Julius Caesar Augustus Germanicus (better known as “Caligula”), ruled A.D. 37—41. The comma-shaped curls that frame the forehead are characteristic of Julio-Claudian portraiture and of Augustus, the first emperor of Rome (reign 27 B.C. — A.D. 14).