Simplify the following text for a Grade 12 native English-speaking person.
Original: Giraffatitan , meaning `` giraffe titan '' , is a genus of sauropod dinosaur that lived during the late Jurassic Period ( Kimmeridgian-Tithonian stages ) .
Simplified: Giraffatitan ( meaning `` giraffe titan '' ) is a genus of sauropod dinosaurs that lived during the late Jurassic Period about 140 million years ago .