Figure 1. ICS Jurassic timeline.[1]

The Jurassic was the second geological period of the Mesozoic era, extending from approximately 201.3 million to 145.0 million years ago. It is divided into Upper, Middle, and Lower epochs.[2] The name "Jurassic" was derived from two previous names for rock layers of Jurassic age. Prussian scientist Alexander von Humboldt was studying a series of carbonate rock deposits in 1799 and named them the "Jura Kalkstein". In 1829, Alexandre Brongniart, a French scientist, used the term "Terrains Jurassiques" which encompassed the Jura Kalkstein rocks and several other rock series. The time period encompassing these rock layers was eventually named the "Jurassic"[3]

Ammonites were a major animal of the Jurassic, experiencing a major diversification. Large marine reptiles were also developing, some of the more famous including the long neck plesiosaurs (Figure 3), short-necked pliosaurs (Figure 4), and dolphin-like ichthyosaurs (Figure 5).[3] On land, dinosaurs were fully dominating. The sauropods (long neck dinosaurs - famous examples include Diplodocus (Figure 6), Brachiosaurus, and Apatosaurus) were the largest land animals to ever exist. Stegosaurs (Figure 7) and the famous carnivore, Allosaurus (Figure 8), also existed at this time. Pterosaurs and early birds, including Archaeopteryx (Figure 9), were beginning to take to the sky. Upper Jurassic shales eventually provide almost half of today's oil and gas source rocks.[4]

Figure 2. Artisit rendition of Jurassic life.[5]

The Pangea supercontinent fully split by the Middle Jurassic, allowing for the development of unique biozones.[3] Wider variations within species developed as they adapted to more varied environments. There were not any major landmasses over either the North or South Poles at this time and no evidence of any glaciation had been found.

Figure 10. The ICS Chronostratigraphic Chart[2]

For Further Reading


  1. International Commission on Stratigraphy."International Chronostratigraphic Chart v2016" Accessed Nov.18, 2018 [Online]. Available: https://www.britannica.com/science/Rhaetian-Stage
  2. 2.0 2.1 International Commission on Stratigraphy."International Chronostratigraphic Chart v2018" Accessed Nov.8, 2018 [Online]. Available: http://www.stratigraphy.org/index.php/ics-chart-timescale
  3. 3.0 3.1 3.2 Gradstein, F. M. "The Geologic Time Scale 2012". Volume 2. 1st ed. Amsterdam ; Boston: Elsevier, 2012.
  4. University of California, Museum of Paleontology."The Jurassic Period" Accessed Nov.18, 2018 [Online]. Available: http://www.ucmp.berkeley.edu/mesozoic/jurassic/jurassic.php
  5. WikiMedia Commons. "File:Europasaurus holgeri Scene 2.jpg" Accessed Nov.18, 2018 [Online]. Available: https://en.wikipedia.org/wiki/File:Europasaurus_holgeri_Scene_2.jpg
  6. WikiMedia Commons. "File:Muraenosaurus l2.jpg" Accessed Nov.18, 2018 [Online]. Available: https://en.wikipedia.org/wiki/File:Muraenosaurus_l2.jpg
  7. WikiMedia Commons. "File:Leedsi&Liopl DB.jpg" Accessed Nov.18, 2018 [Online]. Available: https://en.wikipedia.org/wiki/File:Leedsi%26Liopl_DB.jpg
  8. WikiMedia Commons. "File:Fischsaurier fg01.jpg" Accessed Nov.18, 2018 [Online]. Available: https://en.wikipedia.org/wiki/File:Fischsaurier_fg01.jpg
  9. WikiMedia Commons. "File:Diplodocus BW.jpg" Accessed Nov.18, 2018 [Online]. Available: https://en.wikipedia.org/wiki/File:Diplodocus_BW.jpg
  10. WikiMedia Commons. "File:Stegosaurus BW.jpg" Accessed Nov.18, 2018 [Online]. Available: https://en.wikipedia.org/wiki/File:Stegosaurus_BW.jpg
  11. WikiMedia Commons. "File:Allosaurus BW.jpg" Accessed Nov.18, 2018 [Online]. Available: https://en.wikipedia.org/wiki/File:Allosaurus_BW.jpg
  12. WikiMedia Commons. "File:Archaeopteryx lithographica.jpg" Accessed Nov.18, 2018 [Online]. Available: https://commons.wikimedia.org/wiki/File:Archaeopteryx_lithographica (Berlin specimen).jpg