To continue on that, there would appear to be no aquatic werecreatures in this world. It was a 1000 werecurse small world generated to the year 1000, with plentiful ocean regions.
Furthermore, even though there were caverns, there were no subterranean werecreatures. No weredralthas. There would appear to be only terrestrial ordinary beasts (how boring). Also, it would appear that common things are common and rare things are rare - there must have been like a 50-100x redundancy of werelizards and only a few were-elephants. Will do a test shortly to confirm these.
However interestingly, based on a small sample of 5 different werebeasts, they would all appear to be amphibious despite the creature they're imitating being terrestrial. So a werewhale would actually have no trouble ruining your fortress, if one existed.
EDIT: So, I created a copy of the abundant lizard and called it a "wizard". Generated a similar world - werelizards were abound, but no werewizards. Apparently they're not procedurally generated.
Furthermore there would seem to be a bug, as this world had the age of the "bronze colossus and mountain titan" when the two great powers left were a werecoyote, Duto Dawnedtulips, and a giantess. As the giantess died, the world promptly passed into the age of Duto Dawnedtulips.