Hellenica World

Late Jurassic

The Late Jurassic epoch of the Jurassic Period is the unit of geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago, which is preserved in Upper Jurassic strata.[1] In European lithostratigraphy, the name Malm indicates rocks of Late Jurassic age. In the past this name was also used to indicate the unit of geological time, but this usage is now discouraged to make a clear distinction between lithostratigraphic and geochronologic/chronostratigraphic units.

Subdivisions

The Late Jurassic is divided into three ages, which correspond with the three (faunal) stages of Upper Jurassic rock:
Tithonian (150.8 ± 4.0 – 145.5 ± 4.0 Ma)
Kimmeridgian (155.7 ± 4.0 – 150.8 ± 4.0 Ma)
Oxfordian (161.2 ± 4.0 – 155.7 ± 4.0 Ma)

Paleogeography

Pangaea broke up into two supercontinents, Laurasia to the north, and Gondwana to the south. The result of this break-up was the spawning of the Atlantic Ocean. However, at this time, the Atlantic Ocean was relatively narrow.

This period was well known for many famous types of dinosaurs, such as the sauropods, the theropods, the thyreophorans, and the ornithopods. Other animals, such as crocodiles and the first birds, appeared in the Jurassic. Here are only a few of the many Jurassic animals:

*
o Camarasaurus a large herbivorous sauropod dinosaur from North America.
o Brachiosaurus a large herbivorous sauropod dinosaur from North America.
o Diplodocus a large herbivorous sauropod dinosaur from North America.
o Supersaurus possibly the largest North American sauropod of them all.
o Dicraeosaurus a large herbivorous sauropod dinosaur from Africa.
o Giraffatitan another large sauropod from Africa (usually recognized as a species of Brachiosaurus).
o Allosaurus the most common late Jurassic theropod of North America, also present in Europe.
o Epanterias one of the largest Jurassic carnivores, from North America (possibly just Allosaurus).
o Torvosaurus possibly the largest Jurassic carnivore of all, from North America and Europe.
o Ceratosaurus a medium sized Jurassic carnivore of North America, Europe, and possibly Africa.
o Compsognathus a small theropod from Europe.
o Yangchuanosaurus a large theropod from Asia.
o Tuojiangosaurus a thyreophoran from Asia.
o Stegosaurus a thyreophoran from North America and Europe.
o Dryosaurus a North American ornithopod.
o Camptosaurus an ornithopod from North America and possibly Europe.
o Gargoyleosaurus a thyreophoran from North America.
o Archaeopteryx the first known bird, from Europe.
o Rhamphorhynchus a long-tailed pterosaur from Europe.
o Pterodactylus a short-tailed pterosaur from Europe.
o Ophthalmosaurus a very common sea-going ichthyosaur from what is now Europe and North America.
o Liopleurodon a very large sea-going pliosaur from what is now Europe.


References

1. ^ Owen 1987.

* Owen, Donald E. (March 1987). "Commentary: Usage of Stratigraphic Terminology in Papers, Illustrations, and Talks". Journal of Sedimentary Petrology 57 (2): 363–372. Reproduced here.
* Kazlev, M. Alan (2002-06-28). "Late Jurassic — The Malm Epoch: The Acme of the Dinosaurs". Palæos. http://www.palaeos.com/Mesozoic/Jurassic/LateJura.html. Retrieved 2007-04-11.

Geologic time scale

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