My theory is that Aona and Skai were splintered into the Seons and Skaize.
But I'm also of the opinion that Elantris happens long after Odium's visit, and that the Reod was just a side effect of the fact that the Gods of the world were dead and no longer maintaining their religions or systems of magic, and thus things could break all on their lonesome.
Actually, in thinking about this, I wanted to discuss the evidence for and against this.
The first thing I would note is that the Dor, as found in Elantris, is apparently utterly without consciousness. It is clearly the power of a Shard, or perhaps the combined power of two shards. As far as I can tell from the text, it has not had a consciousness for as long as people have a memory of knowing about it. This comes from several facts: the fact that the Dor still apparently the works the way it did pre-Reod, with only the Chasm line having changed, that the Elantrian's had to scientifically work out how to get it to behave even before the Reod, that the Jesker religion had been studying it for quite some time, apparently thinking of it as a force of nature rather than a consciousness. Basically, it is very easy to read Sel's history as a history without a god intervening for quite a while, with the Dor just kind of sitting there for anybody to use if they can find a way of attuning. The fact that the Elantrian's are worshipped as gods is a pretty good indicator that any other gods whose power they were taking has long since been forgotten.
I'm also pretty sure that the powers of the Shards haven't been destroyed. They probably can't be; the Dor is still around, after all. In fact, they're probably still on Sel. The only question is: what form are they in?
That's part of why I think they are connected to the Seons and the Skaze. Those---entities---have a consciousness, and so are clearly connected to the cognitive realm. They seem to be immortal, and the Elantrian's have no records of how to create them. They are an anomaly. Where does their consciousness come from? I suspect it is a small piece of the consciousness of their respective Shard, long since shattered into pieces.