Phosphatic hard tissues of marine invertebrates: Their nature and mechanical function, and some fossil implications

Abstract

Phosphatic substances are described from hard tissues of species from seven classes of marine invertebrates. Francolite is identified in the species of one class and amorphous calcium- and ferric phosphates, apparently in the form of hydrogels, are recognized as precipitates of species from six other classes. Considering all known phosphatic substances in animal hard parts, it is found that amorphous constituents are far more common in invertebrates than crystalline compounds. The role of amorphous precipitates in providing physical strength to hard parts is examined. Brief comparison is made between phosphate fixation in the phyla spectrum of recent and fossil invertebrates.