Biogenic calcite granules-Are brachiopods different?

► SEM and AFM analyses of biomineral structures in brachiopod shells reveal a complex and distinctive style of biomineralization among carbonate-producing organisms. ► Basic carbonate biomineralization mechanisms are not uniform within the Phylum Brachiopoda. ► Calcite fibers of rhynchonelliform brachiopods, mainly within the Order Terebratulida, have large (>100 nm), triangular particles that are exceptional among carbonate-producing organisms. ► Proteinaceous envelopes surrounding calcite fibers have a dual function as producers of granules as well as organic templates for the orientation of particles and granules inside mineralized fibers. ► Results may provide independent support for the presence of amorphous calcium carbonate (ACC) in this phylum.