Smithsonian National Museum of Natural History Geologic Time The Story of a Changing Earth
Presented by the Department of Paleobiology.
The Jurassic
Contents
Overview
Jurassic Life
Diversity in the "Age of Dinosaurs"
Flight and the Origin of Birds
Jurassic Climate and Tectonic Activity
Evidence
Skeleton of Camarasaurus
learn more
sample
Allosaurus fragilis
Diplodocus longus
Camptosaurus dispar
Ceratosaurus nasicornus
Stegosaurus stenops
Archaeopteryx lithographica
Lytoceras cornucopiae
Promicroceras planicosta
Crocodilian
Ichthyosaur
Dragonfly
Walking stick
Norfolk Island pine
Ginkgo leaf
references and links
Foundational Concepts
Dating Methods
Earth Processes
Life Processes
Privacy Statement Copyright
Glossary Credits Email Us


OVERVIEW
Jurassic 200–146 mya
Defining Characteristics:
  • • ”The Age of Dinosaurs”: dinosaurs become very diverse, evolving into stegosaurs, theropods, and huge sauropods
  • • Map of the Jurassic World
Secondary Characteristics:
  • • origin of birds
  • • origin of the parasitic feeding guilds in terrestrial ecosystems—possibly replacing predators as top insect carnivores
  • • Pangea continues breaking apart, and is better separated toward the end of the Jurassic, with a lush, warm tropical climate

The name Jurassic comes from the Jura Mountains, an extension of the Swiss Alps into eastern France, where rocks of this age were first studied. They were first identified as the Jura Kalkstein (“Jura Limestone”) by Alexander von Humboldt in 1799, and later termed the Terrains Jurassiques by Alexander Brongniart. The rocks were officially named the Jurassic System by Leopold von Buch in 1839. Formed approximately 144–206 million years ago, Jurassic rocks have now been found on every continent.

Pangea was centered on the equator for most of the Jurassic Period, and Earth’s climate was decidedly tropical. During the Early Jurassic, some regions of the world were still arid, but by the Late Jurassic much of the planet was lush. Great rivers covered North America, and the land was green with ferns, seed ferns, cycads, ginkgos, and conifers. It was the ideal environment for the largest animals ever to walk on Earth—giant sauropods such as Diplodocus, as well as many other types of large dinosaurs. Like today, much of the land was covered with trees, although flowering plants had not yet evolved. And, like today, there were many understory plants such as ferns, cycads, and horsetails, but there was no grass for smaller animals to hide in. Because of the dinosaurs’ dominance, mammals were still no larger than rats but had begun to diversify by the Early Jurassic. The Jurassic seas were filled with many types of sharks, bony fishes, marine crocodiles, and other marine reptiles of all sizes. Cephalopods such as ammonites propelled themselves through the oceans. Birds evolved and began to diversify during the Late Jurassic, but the most common flying vertebrates were the reptilian pterosaurs. By the end of the Jurassic, major parts of Europe and North America had become flooded as sea level rose, and Pangea continued to break apart. As North America and Eurasia drifted away from Africa and South America, the Atlantic Ocean was born, creating a barrier for land travel between these regions.


=

Overview | Jurassic Life | Diversity in the “Age of Dinosaurs”
Flight and the Origin of Birds | Jurassic Climate and Tectonic Activity



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