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The Precambrian is an informal unit of geologic time, [3] subdivided into three eons (Hadean, Archean, Proterozoic) of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago ( Ga ) to the beginning of the Cambrian Period, about 538.8 million years ago ( Ma ), when hard-shelled creatures first appeared in ...
The Paleozoic (/ ˌ p æ l i. ə ˈ z oʊ. ɪ k,-i. oʊ-, ˌ p eɪ-/ PAL-ee-ə-ZOH-ik, -ee-oh-, PAY-; [1] or Palaeozoic) Era is the first of three geological eras of the Phanerozoic Eon. . Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic (the last era of the Proterozoic Eon) and ends 251.9 Ma at the start of the Mesozoic Er
The Precambrian includes approximately 90% of geologic time. ... The Phanerozoic is divided into three eras – the Paleozoic, the Mesozoic and the Cenozoic.
It is the latest of three geological eras of the Phanerozoic Eon, preceded by the Mesozoic and Paleozoic. The Cenozoic started with the Cretaceous–Paleogene extinction event, when many species, including the non-avian dinosaurs, became extinct in an event attributed by most experts to the impact of a large asteroid or other celestial body ...
2.1 Selected Paleozoic taxa of Virginia. 3 Mesozoic. 4 Cenozoic. Toggle Cenozoic subsection. 4.1 Selected Cenozoic taxa of ... known occurrences of Precambrian ...
The Phanerozoic is divided into three eras: the Paleozoic, Mesozoic and Cenozoic, which are further subdivided into 12 periods. The Paleozoic features the evolution of the three most prominent animal phyla, arthropods, molluscs and chordates, the last of which includes fish, amphibians and the fully terrestrial amniotes (synapsids and sauropsids).
The Mesozoic is the middle of the three eras since complex life evolved: the Paleozoic, the Mesozoic, and the Cenozoic. The era began in the wake of the Permian–Triassic extinction event , the largest mass extinction in Earth's history, and ended with the Cretaceous–Paleogene extinction event , another mass extinction whose victims included ...
c. 251.9 Ma ± 0.024 Ma – Mesozoic era and Triassic Period begin. Mesozoic Marine Revolution begins. c. 245 Ma – First ichthyosaurs. c. 240 Ma – Cynodonts and rhynchosaurs diversify. c. 225 Ma – First dinosaurs and teleosti evolve. c. 220 Ma – First crocodilians and flies. c. 215 Ma – First turtles.