One could easily miss the bryozoans (entoprocts) or mistake them as an algae or coral. Bryozoans are microscopic individuals (termed zooids) that live in sessile colonies of genetically identical members.  Having said that, there are several notable exceptions: a genus of solitary species (Monobryozoan), and a genus of mobile species (Christatella), and a recently found planktonic species (in genus Alcyonidium) that floats as a ball (Peck et al. 1995).  Known also as “moss animals,” there are somewhere between 4000-6000 living species. About 15,000 fossil species have been found, dating from the early Ordovician.  The fact that no fossils exist from the slightly earlier Cambrian period (in which almost all other invertebrate phyla are found) together with molecular phylogenetic analyses suggest that the earliest bryozoans were non-calcified and thus did not fossilize (Fuchs et al. 2009), but may have in fact originated during the Cambrian.