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
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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
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Jurassic Life
Rising sea levels flooded many of the continental interiors during the Jurassic, creating warm, shallow-water environments where marine animals and plants could thrive. These regions saw an increase in diversity of microscopic phytoplankton such as coccolithophores, dinoflagellates, and foraminiferans. Reef ecosystems continued to flourish, thanks to many species of corals and sponges. Among these sessile (stationary) organisms lived gastropods (snails), along with the now-rarer brachiopods and crinoids. In the waters above swam predatory cephalopods such as ammonoids and belemnites. Sharks and bony fishes remained common and shared the seas with ichthyosaurs, plesiosaurs, and other marine reptiles. The first true marine crocodiles had appeared, alongside the first true teleost fishes (which today are the most diverse vertebrates on Earth).

Fresh-water environments were home to many invertebrates, amphibians, turtles, and crocodilians, as in the Triassic. On land, herbivorous insects diversified, and we see the first examples of many modern forms such as leaf hoppers, snakeflies, and wasps. One extinct group, the Kalligrammatidae, a group related to lacewings, possessed large, conspicuous wings with big “eyespots.” These insects, with their fluid-feeding mouthparts, probably were ecologic analogs to modern butterflies. Beetles—the most diverse group of organisms on Earth today—began their diversification during the Jurassic as well. Some modern groups of beetles had evolved by this time and fed on conifers, cycads, and ferns just as their descendents do today. Flies, beetles and caddisflies diversified in aquatic habitats, feeding in a variety of ways including filtering, collecting and shredding detritus, eating living plants, and preying on other aquatic organisms.

Sphenodontians and the first lizards may have preyed upon many kinds of adult and larval insects. All these animals lived in terrestrial environments with abundant gymnosperm trees, but flowering plants were still absent. The understory plants included ferns, horsetails, and cycads, but grasses (a type of flowering plant), had not yet evolved.



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



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