Initially it was probably not understood as a portrait of Jesus, but a symbol like others used in Early Christian art,[7] and in some cases may also have represented the Shepherd of Hermas, a popular Christian literary work of the 2nd century.[8][9] However, by about the 5th century, the figure more often took on the appearance of the conventional depiction of Christ, as it had developed by this time, and was given a halo and rich robes,[10] as on the apse mosaic in the church of Santi Cosma e Damiano in Rome, or at Ravenna (right). Images of the Good Shepherd often include a sheep on his shoulders, as in the Lukan version of the Parable of the Lost Sheep.[11]