Final answer:
The statement refers to the Cambrian explosion, a period marked by a rapid diversification of marine life, including invertebrates with shells. Trilobites were significant members of this diversification. This event is crucial in understanding the evolutionary history of animal life on Earth.
Step-by-step explanation:
This statement refers to a period in Earth's history known as the Cambrian explosion, which occurred around 541 million years ago. During this time, there was an unprecedented increase in the diversity and complexity of marine life, including a great variety of invertebrates with shells that first appear in the fossil record.
Among the most dominant species of this era were trilobites, a group of early arthropods with a significant number of species. The Cambrian explosion marks an important event in evolutionary history, as many modern animal phyla first appeared during this time.
Collecting fossils from rock layers deposited prior to the Permian period can reveal important information, such as early vertebrate bones, but the most noteworthy event of the Cambrian explosion was the rapid diversification of invertebrates.
Changes in the generic richness of marine invertebrates throughout history, such as those documented by Alroy et al. (2008), also underscore the significant impact of this evolutionary milestone.