Complex sentence: That night, as Littlefoot follows a "hopper," he encounters Cera again, and they play together briefly until a "Sharptooth" attacks them, and Littlefoot's mother comes to their rescue.
Split into simpler sentences: That night, as Littlefoot follows a "hopper," he encounters Cera again, and they play together briefly until a "Sharptooth" appears. He attacks them, before Littlefoot's mother comes to their rescue.