The Qur'an was initially preserved on the following except

The Qur'an was initially preserved on memory, leather, and rock, but not on paper. During the time of Prophet Muhammad (SAW), the primary means of preserving the Qur'an was through memorization, as many of the Prophet's companions had memorized the entire text. In addition to oral transmission, the Qur'an was also written on materials such as animal skins, bones, and stones. However, paper was not yet available during the time of the Prophet, and only became a common material for writing after the Muslim conquests. Therefore, the correct answer is paper.