A Ramnuan Landscape

When, in A Stone In Heaven, Poul Anderson describes a Ramnuan landscape, he makes clear that, apart from the autumnal light, the scene is unEarthlike:

a river flows too fast;
leaves are large, cup-shaped and several colors but not green;
tall grass-like "pyrasphale" hides herds of small animals though not the giant onsars, just large enough for a man to mount;
an onsar is like a rhinoceros with a hump, dorsal fin and extensors ending in clawed, prehensile tendrils.

Meter-high Ramnuans have emerged from forests and hills to conquer the plains by riding onsars from which they see prey and glide towards it. There is more to be said on a future occasion about Ramnuan society.