Half a billion-year-old spiny slug reveals the origins of molluscs

Unlike most molluscs, Shishania did not have a shell that covered its body, suggesting that it represents a very early stage in molluscan evolution. Credit: G Zhang/L Parry. Complete specimen of Shishania aculeata seen from the dorsal (top) side (left). Credit: G Zhang/L Parry. Credit: G Zhang/L Parry.