Siliconium
From one of the last remaining relic populations of Protosagania and through a mixture of selective pressure and horizontal gene transfer, Siliconium evolved. It is a very small, very simple photosynthesizing cell making use of orange pigment to absorb blue light. Uniquely, however, in addition to performing ordinary photosynthesis which uses water and carbon dioxide, it also uses sunlight to break up silicon dioxide which it takes in from quartz in the sediment; it uses this in combination with carbon, oxygen, and other materials (including methane) to produce various forms of silicone, which serves as a defense measure against filter feeders and predatory cells. Its cell membrane is coated in silicone resin, which causes it to pass through the digestive system of most organisms at the time it evolved without issue as they cannot break down this material.