Complex sentence: The Jungle River ride, while mentioned does not appear in the motion picture it was however a large part of the novel during which Grant, Lex and Tim must evade the Tyrannosaurus at the edge of the river.
Split into simpler sentences: The Jungle River ride, while mentioned, does not appear in the motion picture. It was, however, a large part of the novel during which Grant Lex and Tim must evade the Tyrannosaurus at the edge of the river.