How did claw snail fossils form?

A long-time fossil of claw snails. According to relevant data, claw snail fossils are fossils formed by claw snails over a long period of time. The shell of claw snail fossils is loose and coiled, and the shell steps are not connected with each other, and the size of shell steps increases rapidly. The stronger ribs with nodules are separated by two or three slender and fragile ribs without nodules, and the abdomen is round.