Dinosaurs exist in-setting. The K-T extinction event of this earth was not as marked as that of our earth. Ancient megasaurians were only extinct in higher latitudes; they remained in the tropics, thriving every bit as much as the megafauna and intelligent mammals found elsewhere in the world.
Modern dinosaurs are smaller, feathered, gracile and domesticated: they resemble birds more than lizards. Large predatory forms exist only in the jungles and open ocean.
We know...
-Hadrosaurs are used in place of horses in some areas; war/hunting stock can whistle to each other across battlefields
-Also palanquins on tricerotopses
-Dinosaurs protected the Bahamanian natives and the Aztecs from European settlers.
-Some people keep raptor species hunting dogs or hawks.