This silver dish, which has been gilded, shows a legendary dog-headed bird known as a senmurw. This creature first appears in the Late Sasanian period of the 6th century AD in embroidered roundels on textiles. In one tradition it sits on top of the 'Tree of Life' and, by beating its wings, causes the seeds to scatter across the earth. The senmurw is found in modern Iran as the simurgh: it is supposed to be so old that it has already seen the destruction of the world three times. About AD 224 the Parthians were defeated by Ardashir, a descendant of Sasan who gave his name to the new Sasanian dynasty. The new rulers were to reign in Iran for over 400 years. They saw themselves as the successors to the Achaemenid Persians. During the Sasanian period the central government was strengthened, the coinage reformed and Zoroastrianism made the state religion. By the fourth century the Sasanian empire stretched from the Euphrates to the Indus and included Armenia and Georgia. In AD 637, however, the Sassanians were defeated by an Arab army, united under Islam. The last Sasanian king was murdered in AD 651. However, Sasanian artistic traditions continued into the Early Islamic period and the senmurw became a popular subject.