The molluscs are a diverse phylum of Terragen soft-bodied organisms. The body is covered with a thin epidermis or mantle, and teeth (radula) have a distinctive rasp-like structure. Molluscan morphology typically consists of a distinctive head with mouth and/or tentacles (secondarily lost in some forms - e.g. clams), a large fleshy ventral foot, a dorsal visceral hump, and a radular mouth. Most species secrete an external calcareous shell made of aragonite, which is typically curved or coiled in a geometric fashion, or may be composed of multiple parts. Includes chitons (Polyplacophora), snails, whelks, limpets etc. (Gastropoda), clams (Bivalvia), nautiluses, squid, octopus and cuttlefish (Cephalopoda), and a number of smaller extant and several extinct classes. Baseline forms range in size from microscopic snails with shells only 200 microns (0.2 mm) in diameter, to giant squid (Architeuthis) weighting over a tonne.
There were over a hundred thousand Terragen species on Old Earth before the Great Dying; most or all of those that did not survive that event are thought to have been re-created or restored by GAIA either directly or by extrapolation from surviving information. Many of the baseline species are found elsewhere in the Terragen sphere in habs or on terraformed planets, together with a much larger number of derived species. There were many more forms that were already extinct before Terragen civilization arose. Representatives of all pre-Terragen extinct classes and many tens of thousands of extinct species have been lazurogened.
Molluscs, especially cephalopod molluscs, are a popular subject for provolution, despite having a psychology quite different to vertebrates.
The largest bioborged mollusc is the Kraken of the inner Perseus Rift, a sophont, space-adapted creature which is believed to attain a length of many kilometres.