The Cambrian

The Cambrian

The Cambrian is a major division of the geologic timescale that begins about 542 ± 1.0 Ma (million years ago) at the end of the Proterozoic eon and ended about 488.3 ± 1.7 Ma with the beginning of the Ordovician period (ICS, 2004)[2]. It is the first period of the Paleozoic era of the Phanerozoic eon. The Cambrian takes its name from Cambria, the classical name for Wales, the area where rocks from this time period were first studied.
The Cambrian is the earliest period in whose rocks are found numerous large, distinctly fossilizable multicellular organisms that are more complex than sponges or medusoids. This sudden appearance of hard body fossils is referred to as the Cambrian explosion.