Abstract

The first appearance of metazoans during the Ediacaran (575-543 million years ago (Ma)) and calcified skeletons (~553 Ma) has been linked to the widespread development of oxygenated oceanic conditions. The precise environmental context, however, for early animal evolution remains unclear. Spatial and temporal reconstruction of carbon isotope and ocean redox dynamics from the Nama Group, Namibia, shows that the first skeletal animals evolved under conditions of unstable oxygenation. In addition, the choice of biomineral during the Cambrian Radiation was controlled by ecology and metabolic cost. Predation pressure was the escalating force as biominerals were selected according to their principal function (passive defence, active defence, or active predation) under changing physicochemical conditions.

WOOD , R.A., GROTZINGER , J.P. and DICKSON , J.A.D. 2002. Proterozoic modular biomineralized metazoan from the Nama Group. Science 296: 2383-2386.

ZHURAVLEV , A. Yu and WOOD , R.A. 2008. Eve of biomineralization: controls on carbonate mineralogy. Geology 36: 923-926.

WOOD , R. 2011. Paleoecology of early skeletal metazoans: insights into biomineralization. Earth-Science Reviews 106, 184-190.