Middle Jurassic

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Middle Jurassic
174.7 ± 0.8 – 161.5 ± 1.0 Ma
Ammonites Leioceras opalinum and Leioceras lineatum
Lower boundary GSSPFuentelsaz, Spain
41°10′15″N 1°50′00″W / 41.1708°N 1.8333°W / 41.1708; -1.8333
Lower GSSP ratified2000[2]
Upper boundary definitionNot formally defined
Upper boundary definition candidatesHorizon of Ammonite Cardioceras redcliffense.
Upper boundary GSSP candidate section(s)
Middle Jurassic strata of the San Rafael Group, Colorado Plateau.

The Middle Jurassic is the second

Tiouraren Formation of Niger,[6] 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.[citation needed
]

Fauna

The Middle Jurassic is one of the key periods in the

mammals, diversified during this time.[7][8]

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.[citation needed
]

Terrestrial life

Many of the major groups of

ornithopods).[7]

Descendants of the

trithelodonts, were becoming rare and eventually became extinct at the end of this epoch.[citation needed
]

Flora

plants, such as ginkgoes, cycads, and ferns were also common.[citation needed
]

References
  1. ^ "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy.
  2. doi:10.18814/epiiugs/2001/v24i3/003. Retrieved 13 December 2020.{{cite journal}}: CS1 maint: numeric names: authors list (link
    )
  3. doi:10.1007/s12052-009-0137-0
    .
  4. ^ 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.
  5. S2CID 85751613
    . Retrieved 10 April 2023.
  6. doi:10.1016/j.palaeo.2008.10.019
    . Retrieved 12 April 2023.
  7. ^ 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.
  8. PMID 26190074
    .
  9. ^ 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.
  10. ^ Panciroli, E. 2017. The First Mammals Archived 2020-08-03 at the Wayback Machine Palaeontology Online.
  11. ^ Kemp, T 2005. The Origin and Evolution of Mammals. Oxford University Press.
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