what was the cambrian explosion quizlet
Cambrian Explosion. A relatively brief time in geologic history (30-50 MY) when large, hard-bodied forms of animals with most of the major body plans known today appeared in the fossil record. This burst of evolutionary change occurred about 535-525 million years ago. No new major phyla since. relatively brief time in geologic history (30-50 MY) when large, hard-bodied forms of animals with most of the major body plans known today appeared in the fossil record. This burst of evolutionary change occurred about 535-525 million years ago.