Researchers have discovered a new species of mollusc that lived 500 million years ago. The fossil, called Shishania aculeata, is a flat, shell-less slug covered in a protective spiny armour. Some fossils were found preserved upside down, showing that the animal’s bottom was naked, with a muscular foot like a slug.
Experts suggest that this early mollusc would have used its foot to creep across the seafloor. Shishania gives us a unique view into a time in mollusc evolution for which we have very few fossils, informing us that the earliest mollusc ancestors were armoured spiny slugs prior to the evolution of shells.
The new species was found in well-preserved fossils from eastern Yunnan Province in southern China dating from the early Cambrian period, approximately 514 million years ago. The specimens are only a few centimetres long and are covered in small spikey cones made out of chitin, a material also found in the shells of modern crabs, insects, and some mushrooms.
Unlike most molluscs, Shishania did not have a shell that covered its body, suggesting that it represents a very early stage in the evolution of the animal.
Source: https://www.independent.co.uk/news/science/archaeology/octopus-origin-fossil-mollusc-oyester-b2589686.html