Why are calcified bryozoan skeletons commonly preserved as fossils?

Calcified bryozoan skeletons are commonly preserved as fossils because they possess hard, resistant parts that are far more likely to survive the ravages of time than soft tissues, which typically decompose rapidly.12

The zooid walls, which constitute the most permanent portion of the bryozoan colony, are often impregnated with calcium carbonate. This mineralized structure provides the necessary durability for the organism to be preserved in the geologic record. When an organism with such hard parts dies and is quickly buried, minerals from the surrounding sediment can seep into the structure, effectively turning the organic material into stone or creating a detailed stone replica.321

Because of this calcification, bryozoans have a significant fossil record that dates back to the Ordovician Period, approximately 500 million years ago. In contrast, organisms that lack these hard, mineralized parts are poorly represented in the fossil record and are only rarely preserved under exceptional conditions.312