original: extinction non-avian dinosaurs suddenly became extinct approximately 65 million years ago .
simplifications: non-flying dinosaurs suddenly became extinct around 65 million years ago . extinction non-avian dinosaurs suddenly became extinct about 65 million years ago . non-avian dinosaurs became extinct approximately 65 million years ago . 1 . extinction non-avian dinosaurs suddenly became extinct approximately 65 million years ago . non-avian dinosaurs became extinct around 65 million years ago . 65 million years ago , non-flying dinosaurs died out . non-bird dinosaurs suddenly died off about 65 million years ago . non-avian dinosaurs suddenly became extinct approximately 65 million years ago .