Random question about plate tectonics

[BlackAmericanoNoSugar]

This is probably quite a stupid question as I only have a general public's knowledge of the subject, but when articles refer to Pangea they quite often state that there was only one continent on Earth at that time. There is obviously clear evidence that all the continents that we have now were once joined together in one big continent, but I haven't read anything that proves there was no other land. How do we know that there wasn't at least one other continent that has since disappeared under the crust?

Rodinia and Pannotia existed before Pangea. The supercontinent breaks apart then reforms, breaks apart and reforms.

But those are more or less the same bits of land, I was more wondering about the assertion that when Pangea existed it was the only continent. Obviously there were probably volcanic islands and so on, and there are bits of Pangea (and later individual continents) that we now know are underwater. I just find it hard to imagine that there was a big lump of land and one massive ocean surrounding it, it seems odd somehow, unbalanced.

Mmmm interesting point. Plate tectonics is only a theory, albeit a fairly well accepted one. And it does have zones of subduction now, so I guess there could have been other land masses subducted (is that a word?) in the past. Caveat: A level geography only here.