Small shelly fossils

The first stage of the Lower Cambrian is known today as Manykayan (trace fossils), after which come the Pommotian (small shelly fossils), the Atdabanian (trilobites), and the Botomian, while the other two stages of the period are still known with the generic names of Middle and Upper Cambrian (Figure 7.1). 

In the last twenty years, in conclusion, paleontology has discovered that in Cambrian times there have been not one but three different explosions ofanimallife one documented by trace fossils, a second which left behind small shelly fossils, and finally the classical explosion that was dominated by trilobites. It must also be added that Cambrian life was preceded by the so-called Ediacara fauna, a vast assembly of soft-bodied animals (almost all with radial symmetry). Many scholars now regard them as a failed evolutionary experiment, while others believe that they may have left modified descendants (Figure 7.1). 

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