Cretaceous: Overview

Leaf related to the gooseberry family
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Tyrannosaurus rex
Triceratops prorsus
Edmontosaurus annectens
Mosasaurs
Plesiosaurs
Pterosaurs
Ferns
Cycads
Bennettitalean trunks
Coccolithophores
Ammonites
Belemnites
Inoceramids
Rudistids
Diatoms
Foraminifera

references and links

OVERVIEW

Cretaceous 146–65.5 mya

Defining Characteristics:

• extinction of the dinosaurs
• first appearance and diversification of flowering plants
• extreme global warming
• Map of the Cretaceous World

Secondary Characteristics:

• oldest known specimens of termites, ants, and bees
• diversification of birds and many new insect groups
• new kinds of dinosaurs

The name Terrain crétacé (“chalky terrain”) was coined in 1822 by Belgian geologist D'Omalius d'Halloy to refer to the chalk deposits of the Paris Basin, France. Later the name Cretaceous (“chalk-bearing,” from the Latin word creta, meaning “chalk”) came to be used for the many chalk deposits around the world that were formed during this age. One of the most famous examples is the White Cliffs of Dover, England. Such chalks formed from the bodies of billions of single-celled marine algae called coccolithophores. The coccolithophores lived in the sunny surface waters of the ocean, but after death their shells or scales sank to the bottom where they accumulated, were buried, and were compressed to form chalk. Coccolithophores are still important organisms in the oceans today.

The world of the Cretaceous Period (65.5–146 million years ago) brought significant changes to life and to Earth itself. Before this time period, during the Jurassic, animal life on land was dominated by dinosaurs. Some of the dominant plants included ferns, cycads, seed ferns, ginkgos, and conifers. In the seas, marine reptiles (ichthyosaurs and plesiosaurs), sharks, and ammonites were common. Most of these life forms still dominated the Cretaceous world, although new types of dinosaurs and plants also appeared. All of Earth’s landmasses had been clumped together into one huge supercontinent called Pangea, but this had begun to break apart during the Triassic, and seaways had begun to invade Pangea during the Jurassic. By the Cretaceous this process was well under way, making Earth’s climate more equable and greatly affecting both plants and animals.

Overview | Terrestrial Life through the Cretaceous | Life in the Cretaceous Seas
Extinction of the Dinosaurs | Shifting Continents and Greenhouse Climates

Department of Paleobiology Home | National Museum of Natural History Home
Smithsonian Institution Home

chalk

A sedimentary rock of marine origin, formed by the accumulation of calcareous shells (tests) left behind by microorganisms.

Jurassic Period

The second of the three periods of the Mesozoic Era; it lasted from 200 -146 million years ago.

dinosaur

A member of the archosaur class Dinosauria. Dinosaurs (except for birds) are confined to the Mesozoic, and two orders are usually recognized: Saurischia and Ornithischia. The word Dinosauria, as translated in 1842 by its originator, Sir Richard Owen, means "fearfully-great lizard."

cycad

Any member of a group of seed plants with somewhat cone- or leaf-like reproductive organs and leaves that superficially resemble those of some palms. Cycads were moderately common in the late Paleozoic and Mesozoic, and a small number of types survive to the present.

ginkgo

A woody deciduous seed plant with distinctive fan-shaped leaves. Ginkgos, which first appeared in the Permian, are known as "living fossils" because the sole living species (Ginkgo biloba) closely resembles fossils from the Mesozoic.

conifer

Any member of the conifer lineage of seed plants that have cone-like reproductive structures, and typically have needle or scale-like leaves. Pines and redwoods are examples of living conifers. Confiers were common trees in the late Paleozoic and Mesozoic and remain abundant in some environments today, although they are much less diverse than the flowering plants.

ammonite

Any member of an extinct suborder of cephalopod mollusks (Ammonoidea) with chambered, spiral shells that thrived in the Mesozoic and Paleozoic oceans.

supercontinent

A mass of land comprising more than one continental plate.

Pangea

The supercontinent that included all the modern continental masses. Pangea came together in the Permian and began to split up during the Late Triassic. The northern portion of Pangea is called Laurasia, the southern part Gondwana.