The T.rex-Triceratops war was (obviously) a battle between T. rexes and Triceratops. It is only mentioned in Arx's Astro-file in Megabookasaurus! His parents were supposedly killed in it, since they weren't mentioned in his file - plus, Arx was born during a bombing raid, meaning that they could have been blown up. (ouch!) It is unknown who won, but it appears that the Triceratops stole the victory, thanks to Arx's liberty to become a Triceratops Star-Cruiser pilot, as well as being the youngest ever. The war supposedly lasted about eighteen years.