Phylum Mollusca (digitalatlasofancientlife.org) With over 70,000 living species (Rosenburg, 2014), the phylum Mollusca is second only to the Arthropoda in terms of total species diversity. The great diversity of mollusks is owed at least in part to their success in occupying most habitats on earth, including the marine realm, freshwater lakes and rivers, and even land. Some are filter feeders, some are herbivores, and some are deadly predators. The strong, easily-preserved shells of mollusks have left behind a rich Cambrian to Pleistocene fossil record and they have long been important subjects of macroevolutionary analyses of the fossil record.