Or having yet to be dreamt by the Planet, who knows?
No, because they existed in the Dragonian world already, but until Lavos was defeated, and sent to the DBT like Schala, when Belthasar had to start his plan, only then did they come into Another World when Chronopolis was sent back in time, and you should know that.
Well, actually, in a way, I guess you could say it hadn't been dreamt yet, but the planet's dream never stopped after CT anyway. And Dinopolis was simply a counter measure to Chronopolis.