The MISC@1 do not have a true endoskeleton in the evolutionary sense ; here , a mollusc exoskeleton evolved into several sorts of internal structure , the `` cuttlebone '' of cuttlefish being the best-known version .

The MISC@1 do not have a true endoskeleton in the evolutionary sense ; here , a mollusc exoskeleton developed into several sorts of internal structure , the `` cuttlebone '' of cuttlefish being the best-known version .
