The Evolution of Mineral Skeletons

Abstract

All of the major skeletal minerals (calcite, magnesian calcite, aragonite, apatite and opal) and most of the major kinds of skeletal materials (fibrous apatite, spherulitic aragonite, nacre, crossed-lamellar aragonite, foliated calcite, echinoderm stereom etc.) appeared abruptly in many different kinds of organisms at the beginning of the Phanerozoic (570 million years to Recent). Almost all of the clades known to form mineral skeletons originated in the Cambrian Period of earth history (570–505 million years ago) and hardly any kinds of marine organisms developed new types of mineral skeletons after that time. Recent work on the earliest skeletal fossils provides little support for the view that phosphatic skeletons were more common than carbonate skeletons when hard parts first developed.