Complex sentence: Earl Douglass was an American paleontologist (linda) who discovered the dinosaur "Apatosaurus," (Smithson) playing a central role in one of the most important fossil finds in North America.
Split into simpler sentences: Earl Douglass was an American paleontologist (linda) who discovered the dinosaur "Apatosaurus" (Smithson). Douglass played a central role in one of the most important fossil finds in North America.