Question

What important event in animal evolution marks the beginning of the Cambrian period?

Answer 1

the apperance of fossils

Step-by-step explanation:

it is whan the fossils were first found.

Answer 2

The event in animal evolution that marks the beginning of the Cambrian period is the evolution of chordates and arthropods. Chordates are animals with a dorsal nerve cord and arthropods are the ancestors of crustaceans and insects. Hope this answers the question.