Complex sentence: His partner on this arduous journey was an Argentinian of Russian descentMary Reznik (1914--1996), and together they spent nearly a year exploring tribes along the Araguaia and Rio das Mortes Rivers.
Split into simpler sentences: His partner on this arduous journey was an Argentinian of Russian descent Mary Reznik (1914--1996). Together they spent nearly a year exploring tribes along the Araguaia and Rio das Mortes Rivers.