Carracks are regarded as the immediate predecessor of the galleon in terms of ship design. They were the first large square-rigged ships to ply the seas and were valued because of their large capacity for carrying troops or cargo.
Carracks differed from galleons in that they were still primarily medieval ships built with an emphasis on winning a medieval style battle. The design emphasis was not on sailing quailities and artillery capacity, but with building a ship resistant to enemy boarding parties. (To a lesser extent this is true of the galleon as well and contributed to its eventual demise as a ship design) To repel boarders the aft and forecastles were built up as towering fortresses bristling with archery or gun slits.