Phanerozoic

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Dalmanites limulurus trilobite silurian

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Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers roughly 541 million years and is divided into three geologic eras: the Paleozoic, Mesozoic, and Cenozoic eras. The Phanerozoic follows the Proterozoic Eon and is followed by the Anthropocene, a proposed epoch that begins with significant human impact on Earth's geology and ecosystems.

Overview

The term "Phanerozoic" derives from Greek and means "visible life", referring to the period in Earth's history when life forms with hard parts began to proliferate. This eon is characterized by the significant development and diversification of life, particularly multicellular organisms. The Phanerozoic Eon has witnessed the rise and fall of many species and has been marked by significant evolutionary events, including the Cambrian Explosion, the Permian-Triassic Extinction Event, and the Cretaceous-Paleogene Extinction Event.

Divisions

The Phanerozoic Eon is divided into three eras, each of which is further subdivided into periods.

Paleozoic Era

The Paleozoic Era is the oldest era of the Phanerozoic Eon, spanning from about 541 to 252 million years ago. It is divided into six periods: the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. This era is characterized by the development of the first vertebrates, the rise of fish, the dominance of amphibians, and the appearance of reptiles and insects.

Mesozoic Era

The Mesozoic Era follows the Paleozoic Era, extending from about 252 to 66 million years ago. It is divided into three periods: the Triassic, Jurassic, and Cretaceous. The Mesozoic is known as the "Age of Reptiles" due to the dominance of dinosaurs. This era also saw the first birds and mammals, as well as significant plant evolution.

Cenozoic Era

The Cenozoic Era is the current and most recent of the three eras of the Phanerozoic Eon, beginning 66 million years ago and continuing to the present day. It is divided into two periods: the Paleogene and Neogene, and further subdivided into epochs. The Cenozoic is often referred to as the "Age of Mammals" because mammals became the dominant terrestrial animals during this time. This era also encompasses significant climatic changes and the evolution of humans.

Significance

The Phanerozoic Eon is significant because it encompasses the time period during which life on Earth has been most diverse and complex. It includes the evolution of complex life forms with hard parts, such as shells and bones, which are more likely to be preserved as fossils. This eon has provided scientists with a wealth of information about the history of life on Earth, including the dynamics of evolution, extinction events, and the shifting of continents and ocean basins.

See also

• Geologic time scale
• Evolution
• Extinction event
• Fossil