Did Magellan have access to Ancient Maps

Just been catching up on a Voyages of Discovery edition on Magellan’s voyage.  It confidently stated that South America had not been charted below 35 South when Magellan sailed in 1519 – which of course discounts Piri Re’is (1513) entirely.  However it implied that Magellan, who had spent time in the Indian Ocean, had some reason to believe that he would find a sea passage to the Pacific further south.  That belief can’t have been derived from Piri Re’is, who showed Antarctica adjoining Cape Horn.  So was there a separate ancient maps lineage preserved somewhere in Arabia, India or East Africa?