SPONGES: Actinocoelia
Phylum Porifera Actinocoelia maeandrina
The sponge is so simple! Just a loose colony of cooperating single cells—some for catching food with their tiny hair-like cilia, some wandering amoeba-like through the colony to distribute food, some engineering skeletal supports: little needles or stars of silica called spicules. Altered masses of spicules make the white color.
Because the skeleton is silica, altering later to durable chert, the sponge is responsible for making the Kaibab Formation hard and durable. For this reason, erosion has lowered the land only as far as the Kaibab and no farther. Thus, in a sense, the lowly sponge, the softest of creatures, is the reason we have a Grand Canyon instead of a broad valley.