 Complete the following phrase:  The griffin is generally agreed to have arrived in Pisa at some point during the late 11th or early 12th century and may have been a spoil of one of the many successful wars or raids conducted by the Republic of Pisa against Islamic states. In this period, Pisa was at the height of its power as a maritime republic. The successful attack in 1087 on Mahdia in modern Tunisia, the capital of the local Zirid dynasty, is one candidate. Another strong candidate is the 