Complex sentence: The "Pushkin" has the fuel and food from McMurdo to conduct long, thorough explorations of the world, and thus it is the Soviet submarine, and not the USS "Nathan James" that is the "last ship".
Split into simpler sentences: The "Pushkin" has the fuel to conduct long, thorough explorations of the world. Thus it is the Soviet submarine, and not the USS "Nathan James" that is the "last ship".