Complex sentence: The eight living pelican species have a patchy global distribution, ranging latitudinally from the tropics to the temperate zone, though they are absent from interior South America as well as from polar regions and the open ocean.
Split into simpler sentences: The eight living pelican species have a patchy global distribution, ranging latitudinally from the tropics to the temperate zone. They are absent from interior South America as well as from polar regions and the open ocean.