The teaser trailer explains the whole human/dinosaur thing; the asteroid missed, basically, so this is a world where dinosaurs never went extinct, but humans ended up evolving anyway.
However, if you want to be nitpicky, I believe sauropods like the main dinosaur character were already extinct long before the actual KT extinction event that took out the rest of the dinosaurs.
The teaser trailer explains the whole human/dinosaur thing; the asteroid missed, basically, so this is a world where dinosaurs never went extinct, but humans ended up evolving anyway.
However, if you want to be nitpicky, I believe sauropods like the main dinosaur character were already extinct long before the actual KT extinction event that took out the rest of the dinosaurs.