what parts of south america are part of antarctica
South America and Australia were not part of the fabled "Antarctica".
Antarctica
 Even in the late 17th century, after explorers had found that South America and Australia were not part of the fabled "Antarctica", geographers believed that the continent was much larger than its actual size. 
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Antarctica [SEP] History of exploration
Integral to the story of the origin of Antarctica's name is that it was not named "Terra Australis"—this name was given to Australia instead, because of the misconception that no significant landmass could exist further south. Explorer Matthew Flinders, in particular, has been credited with popularising the transfer of the name "Terra Australis" to Australia. He justified the titling of his book "A Voyage to Terra Australis" (1814) by writing in the introduction: European maps continued to show this hypothetical land until Captain James Cook's ships, and , crossed the Antarctic Circle on 17 January 1773, in December 1773 and again in January 1774.