The rapid diversification of multicellular animal life that took place around the beginning of the Cambrian Period. It resulted in the appearance of almost all modern animal phyla. See Note at Burgess Shale.
The Cambrian explosion was caused by a lack of oxygen, not an
Molecular Clock
Burgess Shale and Cambrian Explosion – Hugh Ross – YouTube
Liberal Dictionary | The Cambrian Explosion | 9781936221035 | Douglas H. Erwin