from or referring to the period of time between about 543 and 490 million years ago, in which many different types of invertebrates (= animals with no back bone) first appeared
These rocks date from the middle of the Cambrian era.
They are already present in early Cambrian rocks.
更多例句
Now nobody can deny that life back in the Cambrian era was already extremely varied.
When we consider another event of the Cambrian period, an interesting parallel emerges.
The evidence fitted, but there was something of a gap between the first eye and the Cambrian explosion event.