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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. |
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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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