DeviantArt user Concavenator writes about the planet Ea. Unlike most projects that focus on one ecosystem, this project gets into the interactions of organisms with partly incompatible biochemistries. After several decades of environmental and political turmoil on Earth, humans have moved to Ea to repeat their mistakes – and they’ve brought their cats with them.
Few projects go into as much depth as this one, covering plant reproduction, cellular structure, biochemistry, and so much more. As of this writing, it still only has a few lineages though, including descendants of starfish-like animals, some who have converted one arm into a head, leaving four limbs left over, and some who have merged two arms into a head, leaving three limbs left over. It’s great!