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

Exceptional fossils with preserved soft parts reveal that the earliest mollusks were flat, armored slugs without shells. The new species, Shishania aculeata, was covered with hollow, organic, cone-shaped spines. The fossils preserve exceptionally rare detailed features which reveal that these spines were produced using a sophisticated secretion system that is shared with annelids (earthworms and relatives).