What organisms did molluscs originate from?

Molluscs are primitive aquatic organisms, the origin of which is still not fully understood. It is known that the total number of species of mollusks reaches about 200 thousand, which is quite a lot. Scientists are debating about the origin of molluscs. One suggestion is that they are descended from annelids or flatworms. But that is not the only assumption. It is believed that the distant ancestors of these organisms were coelomic trochophore animals, from which, subsequently, all worms evolved.