Grandes hitos de la Explosión Cámbrica: asociación bentónica macrobioclástica en el Piso cámbrico inferior 2 del Olenek Uplift, Siberia ártica

Abstract

The basal Cambrian Stage 2 strata of the Olenek Uplift host diverse assemblages of macroscopic fossils, which closely resemble certain small skeletal taxa early reported from this section and typical for the Terreneuvian Epoch. Herein studied macroscopic assemblage includes helcionellid, stenothecid and kharkhaniid molluscs, and anabaritids and circothecid hyoliths. Among the assemblage, only anabaritids and some citrcothecid hyoliths exhibit relics of calcite shell, whereas most of the fossils reveal no evidence of rigid biomineralized exoskeleton. Hence, at least these problematic Cambrian organisms had reached macroscopic sizes (up to 35 mm long) and were covered with calcite shells at the very beginning of the Cambrian Age 2.