The creationist that mine the quotes are blatantly dishonest. Those who repeat the mined quotes without double checking are blatantly ignorant. What can one say about a movement relying on dishonesty and ignorance to advance its cause?
Shells are dated as if they were rocks. They are made out of minerals. The shells will take on the age of the minerals they came from. I don't think there are too many methods for dating shells, unless you do radiometric dating of the surrounding rocks in the strata.
Dating fossils with C14 is not often done because there is no carbon left in fossils generally as they have been mineralized. Also, since C14 only dates 50,000 years back, it is not used for dating fossils which go back hundreds of thousands to millions of years.
This whole C14 dating stuff is a purposeful strawman the creationists use to argue their non-science. It is similar to inserting origin of life into evolution and then arguing about something that doesn't exist.
Actually their habitat was pools in limestone rock....
Uh..
I thought most ALL fossils are found in limestone.