How many millions of years ago the continents where distant enough for biotic interchange to stop between them?

For context: I was reading a bit about the origin of angiosperms. I'm surprised many families have a worldwide distribution, even though they are geologically younger tha Pangaea (e.g. Orchidaceae).

I know there are some recent cases like Rhipsalis baccifera, but we can say overall the biotic interchange between separated continents stopped until humans arrived.

So, when did that happen? Try to limit the discussion to the break of Pangaea, so let's keep the Great American Biotic Interchange out.