Start:

Conodont, lowest occurrence of Iapetognathus fluctivagus; just above base of Cordylodus lindstromi conodont Zone. Just below lowest occurrence of planktonic graptolites.

Index Fossils:

Trilobites, Graptolites

Evolution:

Diverse marine life, including vertebrates; vascular plants

Geography:

Similar to the preceding Cambrian period, irratic climate changes

Rocks:

Limestone and Shale