Why are fossils of mollusks more abundant than those of the worm phyla?

Fossils of mollusks are more abundant than those of worm phyla primarily due to the hard, durable shells that many mollusks possess, which are more likely to be preserved in the fossil record. In contrast, most worms have soft bodies that decompose rapidly after death, leaving little to no trace. Additionally, mollusks have diverse habitats and a long evolutionary history, increasing their chances of fossilization. The combination of these factors contributes to the greater abundance of mollusk fossils compared to those of worms.