From New World Encyclopedia
Phanerozoic eon (542 mya - present)
Paleozoic era Mesozoic era Cenozoic era
Cenozoic era
65 - 0 million years ago
Key events in the Cenozoic era
-65 —
-60 —
-55 —
-50 —
-45 —
-40 —
-35 —
-30 —
-25 —
-20 —
-15 —
-10 —
-5 —
0 —
N. Amer. prairie expands[1]
First Antarctic glaciers[2]
Messinian salinity crisis[3]
Holocene begins 11.5 ka ago
An approximate timescale of key
Cenozoic events.
Axis scale: millions of years before present.

The Cenozoic (from the Greek kainos meaning "new" and zoe meaning "life") era is an interval of about 65 million years defined on the geologic timescale as spanning roughly from 65 million years ago (mya) to the present and ongoing into the foreseeable future. The Cenozoic era began after the Cretaceous-Tertiary extinction event at the end of the Cretaceous period that marked the demise of the last dinosaurs and the end of the Mesozoic era.

The fauna and geology of Cenozoic era up to today are vastly different than those of the Mesozoic era, which nonetheless set the stage and foundation for today's fauna and geology. The preceding Mesozoic era has been called the "Age of Dinosaurs," while the present era is sometimes referred to as the "Age of Mammals."

The Cenozoic era is divided into two periods, the Paleogene and Neogene, and they in turn are divided into epochs. The Paleogene period comprises the Paleocene, Eocene, and Oligocene epochs, and the Neogene period comprises the Miocene, Pliocene, Pleistocene, and Holocene epochs, the last of which is ongoing.

Historically, the Cenozoic era has been divided into periods (or sub-eras) named the Tertiary (Paleocene, Eocene, Oligocene, Miocene, and Pliocene epochs) and the Quaternary (Pleistocene and Holocene epochs). However, the International Commission on Stratigraphy (ICS) has decided to stop endorsing the terms Quaternary and Tertiary as part of the formal nomenclature, making the Paleogene and Neogene periods the official nomenclature of the ICS.

Geology of the Cenozoic

Geologically, the Cenozoic is the era when continents moved into their current positions. Australia-New Guinea split from Gondwana to drift north and, eventually, abut South-east Asia. Antarctica moved into its current position over the South Pole. The Atlantic Ocean widened and, later in the era, South America became attached to North America.

Life in the Cenozoic era

Cenozoic era (65-0 mya)
Paleogene             Neogene      Quaternary

The Cretaceous-Tertiary extinction event, known also as the K-T extinction event, occurred about 65.5 million years ago. Approximately 50 percent of all plant and animal families disappeared during this mass extinction, including the non-avian dinosaurs. The most widely accepted current theory for this extinction is that an object from space produced an impact event on Earth.

The K-T extinction event marked the boundary between the Mesozoic era and the Cenozoic era—and between the last period of the Mesozoic (the Cretaceous) and the first period of the Cenozoic, the Paleogene period (or the Tertiary sub-era traditionally).

The Cenozoic era is the “age of mammals.” During the Cenozoic, mammals diverged from a few small, simple, generalized forms into a diverse collection of terrestrial, marine, and flying animals. The Cenozoic era is just as much the age of savannas, or the age of co-dependent flowering plants and insects. Birds also evolved substantially in the Cenozoic.

See also


  1. Retallack, G.J. (1997). Neogene Expansion of the North American Prairie. PALAIOS 12 (4): 380-390.
  2. Zachos, J.C. and Kump, L.R. (2005). Carbon cycle feedbacks and the initiation of Antarctic glaciation in the earliest Oligocene. Global and Planetary Change 47 (1): 51-66.
  3. Krijgsman, W. and Garcés, M.; Langereis, C.G.; Daams, R.; Van Dam, J.; Van Der Meulen, A.J.; Agustí, J.; Cabrera, L. (1996). A new chronology for the middle to late Miocene continental record in Spain. Earth and Planetary Science Letters 142 (3-4): 367-380.

ISBN links support NWE through referral fees

  • Natural History Museum, London. British Caenozoic Fossils (Tertiary and Quaternary). 5th Edition. Intercept, Ltd., 1975. ISBN 1898298777
  • Raymond, A., and C. Metz. “Ice and its consequences: Glaciation in the Ordovician, Late Devonian, Pennsylvanian-Permian and Cenozoic compared.” Journal of Geology 112:655-670, 2004.
  • Redfern, R. Origins: The Evolution of Continents, Oceans and Life. Norman, OK: University of Oklahoma Press, 2001. ISBN 0806133597


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