Original: The Coleoidae 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.
Simplified: The Coleoidae 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.