Dinosaurs

Looking at land masses during the Mesozoic, it appears "China" was never connected to Pangea. Pangea was known for dinosaurs, which raises the question: what was the last common ancestor for dinosaurs in Pangea and in Cathaysia; and where is that common ancestor found? There were no marine dinosaurs. Unlikely that dinosaurs evolved twice at same time but if first dinosaur in Pangea, how did dinosaurs get to China, or vice versa?

There was only one landmass separate from Pangea remaining, Cathaysia, and it was made up of north and south China. It never became part of the supercontinent. Once completely formed, Pangea covered around one-third of the Earth's surface and the rest was ocean (and Cathaysia). Link here. Cathaysia at wiki.

See global land masses in The Princeton Field Guide to Dinosaurs, Gregory S. Paul, c. 2020, pp 56 - 59.