Cenozoic

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Mammals are the dominant terrestrial vertebrates of the Cenozoic.

The Cenozoic (also Cænozoic or Cainozoic) Era (Template:PronEng) (meaning "new life" (Greek Template:Polytonic (kainos), "new", and Template:Polytonic (zoe), "life"), is the most recent of the geologic eras and covers the period from 65.5 million years ago to the present. It is marked by the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and the end of the Mesozoic Era. The Cenozoic era is ongoing.

Subdivision

The Cenozoic Era is divided into two periods, the Paleogene and Neogene, and they are in turn divided into epochs. The Paleogene consists of the Paleocene, Eocene, and Oligocene epochs, and the Neogene consists of the Miocene, Pliocene, Pleistocene, and Holocene epochs, the last of which is ongoing. Historically, the Cenozoic has been divided into periods (or sub-eras) named the Tertiary (Paleocene through Pliocene) and Quaternary (Pleistocene and Holocene). It is known as the age of mammals.

Tectonics

Geologically, the Cenozoic is the era when the continents finished forming into their current topographic configuration.

Australia

Australia-New Guinea split from Gondwana and drifted north and, eventually, adjacent to South-east Asia

Antarctica

Antarctica moved into its current position over the South Pole.

Atlantic Ocean

The Atlantic Ocean widened.

South America

During the Cenozoic South America moved northward toward North America and became attached due to the closure between their plates. From 50 to 25 Ma oceanic plate subduction progressively decreased accompanied by an eastward shift in the loci of magmatic activity in the Andes. At 25 Ma a major reorganization of plate motions to the Chilean Andes was accompanied by subsequent broadening of the locus of magmatic activity into adjacent Bolivia and Argentina.

India

India collided with Asia between 55 and 45 million years ago. This collision set up a series of reactions of tectonic development in Southeast Asia involving the South China Sea, Burma and Thailand, the Malay peninsula to Sumatra.

Arabia

The Arabia–Eurasia collision and the closure of the Tethys ocean gateway began in the Late Eocene at ~ 35 Ma, apparently ending the Eocene greenhouse world.

Climate

The Cenozoic Era has been a period of long-term cooling. After the tectonic creation of Drake Passage, when Australia fully detached from Antarctica during the Oligocene, the climate cooled significantly due to the advent of the Antarctic Circumpolar Current which brought cool deep Antarctic water to the surface. Warm conditions returned in the Miocene due to uncovered gas hydrates releasing carbon dioxide.^ref? When South America became attached to North America creating the Isthmus of Panama, the Arctic region cooled due to the strengthening of the Humboldt and Gulf Stream currents^ref? , eventually leading to the Glacial Maximum or the last ice age.

Life

The Cenozoic Era is the age of new life. During the Cenozoic, mammals diverged from a few small, simple, generalized forms into a diverse collection of terrestrial, marine, and flying animals, giving this period its other name, the Age of Mammals, despite the fact that birds still outnumbered mammals two to one. The Cenozoic is just as much the age of savannas, the age of co-dependent flowering plants and insects, or the age of birds. Grass also played a very important role in this epoch, shaping the evolution of the birds and mammals that fed on it. One group that diversified significantly in the Cenozoic as well were the snakes. Evolving in the Cenozic, the snakes evolved into a huge amount of forms, especially colubrids, following the evolution of their current prey source, the rodents.

In the earlier part of the Cenozoic, the world was dominated by the gastornid birds, terrestrial crocodiles like Pristichampsus, and a handful of primitive large mammal groups like uintatheres, mesonychids, and pantodonts. But as the forests began to recede and the climate began to cool, other mammals took over. The cenozoic is full of mammals both strange and familiar, including chalicotheres, oreodonts, whales, primates, entelodonts, saber-toothed cats, mastodons and mammoths, three-toed horses, giant rhinoceross like Indricotherium, and brontotheres.

See also

• Geologic Time Scale
• K-T Boundary

Bibliography

• British Caenozoic Fossils, 1975, The Natural History Museum, London.
• Geologic Time, by Henry Roberts.