Beginning at the base of the Cambrian period and extending for about 10 million years, all the major groups of skeletonized invertebrates made their first appearance in the most spectacular rise in diversity ever recorded on our planet.
When I view all beings not as special creations, but as the lineal descendants of some few beings which lived long before the first bed of the Cambrian system was deposited, they seem to me to become ennobled. ~ Charles Darwin in The Origin of Species, 6th ed. (1872), page 428. X Y