Diversification of skeletal microstructures of organisms through the interval from the latest Precambrian to the Early Cambrian

Abstract

Research on early skeletal fossils of southern Shaanxi Province and eastern Yunnan Province shows that the interval from the latest Precambrian to the Early Cambrian was an impor-tant period of significant changes in biomineralization of various organisms. The latest Precam-brian skeletal fossils, represented by Cloudina, are characterized by cone-in-cone structures, rela-tively high content of organic matter, and various shell shapes with obvious plastic deformation. In the Early Cambrian the skeletal organisms, consisting of phosphatic, carbonate and siliceous min-erals, began to appear in great abundance and to distribute widely. Moreover, microstructure of these skeletal organisms appeared to have been diversified, for example, main types of recent molluscan microstructures, such as prismatic, lamello-fibrillar and regular foliated structures, were already developed at that time; fibrous structures further diversified, such as lamello-fibrillas in-dicative of mollusks and fibre bundles of hyoliths; there were at least two layers in a shell. This shows that biologically controlled biomineralization had played the main role in the Early Cambrian and it laid a key foundation for formation of the true shell of diverse invertebrates, giving rise to the Cambrian explosion.