The current theories are that the “dinosaurs” were actually big birds, are in no way extinct, and most of us eat them on Shabbos. Animals frequently change size and shape, and this has been observed even in recent years (for examplemedieval cattle were only the size of large sheep, and the variety of dog breeds are quite recent).
There are all sorts of traditions of multiple worlds, so almost anything is possible. The whole concept of “time” is discussed in kaballa (and physics), and is very unclear.