Bryozoans are tiny colonial animals that generally build stony skeletons of calcium carbonate, superficially similar to coral (although some species lack any calcification in the colony and instead have a mucilaginous structure). Members of the Phylum bryozoa are known as “moss animals” or “moss animacules” (which is the literal translation of the Greek term βρυόζωα, “bryózoa”) or as “sea mats”. They generally prefer warm, tropical waters, but are known to occur worldwide. They’ve also been observed to exist in sewer systems, examples being Denver and North Carolina. There are about 8,000 living species, with several times that number of fossil forms known.