For Callunia to appear in the cube, not only does its ancestor, Stromatolite, needs to be around but Cyclomedusa must be as well. The cubes temperature must be rather high and have a decent area of shallows too. After a bit of time with these conditions or by using a Seed of Evolution on Stromatolite, Callunia should appear.
During the story mode, it becomes available during the first episode: The Cube is born.
|Needs to be around for Callunia to appear.|
|No.025 Codium fragile|
|←||No.001 Stromatolite||Organisms||No.003 Baragwanathia||→|