I think I'm going to stop worrying so much about perfect landforms and just wing it until someone complains. Damsback has an Andean mountain range (damsbackbone?) to the east. The mountains are the source of the River, and it flows westward to the sea. I'm not sure how far north the landmass extends. The River is right on the equator. I'd like a tornado alley in the southern grasslands. There's an unobstructed path between the equator and the south pole, but I don't know if the jungle will do anything to the moisture coming from the sea north of the continent.

Speaking of the sea, I'm not sure if the yinrih's range extended eastward all the way to the coast. Perhaps the swampy river delta is home to several disease vectors that keep yinrih and tree dwellers from migrating to the coast. At any rate, the yinrih don't discover the ocean until after they begin populating the southern grasslands. The primordial word for ocean literally translates to “water prairie”.

There is at least one other large landmass besides Damsback, but I wonder if the yinrih don't discover it until after they achieve spaceflight. “Oh wow, would you look at that, there's a whole other continent that's been there the whole time.”