Key biostratigraphic fossil events are tied to specific geological time boundaries: trilobite extinction, ammonite extinction, earliest complex trace fossils, and the earliest Ediacaran soft-bodied fauna.
Trilobites went extinct at the end of the Palaeozoic (Permian-Triassic boundary) (A-R). Ammonites went extinct at the end of the Cretaceous (K-Pg boundary) (B-S). The...
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