Middle Jurassic
| Middle Jurassic | |
|---|---|
Ammonites Leioceras opalinum and Leioceras lineatum | |
| Lower boundary GSSP | Fuentelsaz, Spain 41°10′15″N 1°50′00″W / 41.1708°N 1.8333°W |
| Lower GSSP ratified | 2000[2] |
| Upper boundary definition | Not formally defined |
| Upper boundary definition candidates | Horizon of Ammonite Cardioceras redcliffense. |
| Upper boundary GSSP candidate section(s) | |
The Middle Jurassic is the second
Daohugou Beds in China, the Itat Formation in Russia, and the Isalo III Formation
of western Madagascar.
Paleogeography
During the Middle Jurassic Epoch,
subduction zone on the coast of western North America continued to create the Ancestral Rocky Mountains
.Significant subduction zones were active along practically all of the continental edges surrounding Pangea, as well as in southern Tibet, southeastern Europe, and other locations, to allow the formation of fresh seabed in the proto-Atlantic Ocean. Plate tectonic activity in subduction zones caused the construction of north-south mountain ranges such as the Rocky Mountains and the Andes all along the west coast of North, Central, and South America.
Fauna
The Middle Jurassic is one of the key periods in the history of life on Earth. Many groups, including dinosaurs and mammals, diversified during this time.[5][6]
Marine life
During this time,
metriorhynchids
first appeared. In the Jurassic seas, a wide range of animals swam. Cartilaginous and bony fish were plentiful. Large fish and marine reptiles were plentiful.
Terrestrial life
Many of the major groups of
ornithopods).[5]
Descendants of the
trithelodonts, were becoming rare and eventually became extinct at the end of this epoch.[citation needed
]
Flora
Conifers were dominant in the Middle Jurassic. Other plants, such as ginkgoes, cycads, and ferns were also common.
References
- ^ "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy.
- . Retrieved 13 December 2020.
- .
- ^ British Geological Survey. 2011. Stratigraphic framework for the Middle Jurassic strata of Great Britain and the adjoining continental shelf: research report RR/11/06. British Geological Survey, Keyworth, Nottingham.
- ^ a b Benson RBJ, Campione NE, Carrano MT, Mannion PD, Sullivan C, Upchurch P, and Evans DC. 2014. Rates of dinosaur body mass evolution indicate 170 million years of sustained ecological innovation on the avian stem lineage. PLoS Biology 12, no. 5: e1001853.
- PMID 26190074.
- ^ Kielan-Jaworowska, Z., Cifelli, R.L., and Luo, Z.-X. 2004. Mammals from the age of dinosaurs: origins evolution and structure. 630 pp. Columbia University Press, New York.
- ^ Panciroli, E. 2017. The First Mammals Archived 2020-08-03 at the Wayback Machine Palaeontology Online.
- ^ Kemp, T 2005. The Origin and Evolution of Mammals. Oxford University Press.
