Called Shishania aculeata, the new fossil reveals that the earliest molluscs (animals that do not have a backbone) were flat, shell-less slugs covered in a protective spiny armour. Some of the ...

“Trying to unravel what the common ancestor of animals as different ... mollusc ancestors were armoured spiny slugs, prior to the evolution of the shells that we see in modern snails and clams.” ...

and spiny, oval carapaces blend in with the rocks on the ocean floor. Those round shells and long legs give Japanese spider crabs an arachnid-like look, hence their common name. These animals also ...