Siilun

Siilun is an Earth-like planet with three continents in a binary planet system within a trinary star system. It and its sister planet, Leiko, are both home to life, though the life that exists on Leiko tends to be much less complex that the life that exists on Siilun.

There are two genera of sapient species on Siilun- the Saan genus, which dominates the smaller continents of Katiin and Tengokai, and the Shoram genus, which is dominant on the larger continent of Maresh. The Saan genus is relatively human, while the Shoram genus is relatively cat-like. The two genera evolved separately and from distinct mammalian orders. All mammalian species on Siilun (including both sapient genera) have three common sets of sexual characteristics, generally leading to very different social structures than those seen on Earth.

It should be noted that this is not primarily a project of worldbuilding, but of conlanging. The world exists as a context for the languages which exist within it, which are often more extensive and researched than the world itself, although I try to take care with that as well.