Kimmeridgian

System/
Period		 Series/
Epoch		 Stage/
Age		 Age (Ma)
Cretaceous Lower/
Early		 Berriasian younger
Jurassic Upper/
Late		 Tithonian 145.0–152.1
Kimmeridgian 152.1–157.3
Oxfordian 157.3–163.5
Mid/
Middle		 Callovian 163.5–166.1
Bathonian 166.1–168.3
Bajocian 168.3–170.3
Aalenian 170.3–174.1
Lower/
Early		 Toarcian 174.1–182.7
Pliensbachian 182.7–190.8
Sinemurian 190.8–199.3
Hettangian 199.3–201.3
Triassic Upper/
Late		 Rhaetian older
Subdivision of the Jurassic system
according to the IUGS, as of July 2012.

In the geologic timescale, the Kimmeridgian is an age or stage in the Late or Upper Jurassic epoch or series. It spans the time between 157.3 ± 1.0 Ma and 152.1 ± 0.9 Ma (million years ago). The Kimmeridgian follows the Oxfordian and precedes the Tithonian.[1]

Stratigraphic definition

The Kimmeridgian stage takes its name from the village of Kimmeridge on the Dorset coast, England. The name was introduced in literature by Swiss geologist Jules Thurmann in 1832. The Kimmeridge Clay Formation has its name from the same type location. It is the source for about 95% of the petroleum in the North Sea.

Historically the term Kimmeridgian has been used in two different ways. The base of the interval is the same but the top was defined by British stratigraphers as the base of the Portlandian (sensu anglico) whereas in France the top was defined as the base of the Tithonian (sensu gallico). The differences have not yet been fully resolved, but Tithonian is now seen as the uppermost stage of the Jurassic in the timescale of the ICS.[2]

The base of the Kimmeridgian is at the first appearance of ammonite species Pictonia baylei in the stratigraphic column. A global reference profile for the base (the GSSP of the Kimmeridgian stage) had in 2009 not yet been assigned. The top of the Kimmeridgian (the base of the Tithonian) is at the first appearance of ammonite species Hybonoticeras hybonotum. It also coincides with the top of magnetic anomaly M22An.

Subdivision

The Kimmeridgian is sometimes subdivided into Upper and Lower substages. In the Tethys domain, the Kimmeridgian contains seven ammonite biozones:

Palaeontology

†Ankylosaurs

Ankylosaurs of the Kimmeridgian
Taxa Presence Location Description Images
    		 Morrison Formation, Wyoming, USA The smallest and the earliest well-known ankylosaur. Its skull measures only 29 cm in length, and its total body length is an estimated three to four meters.
    Gargoyleosaurus skeleton
    • Mymoorapelta maysi
    		 Morrison Formation, Colorado, USA A poorly known early ankylosaurian.

    Birds

    Birds of the Kimmeridgian
    Taxa Presence Location Description Images
    • Archaeopteryx lithographica
    A model depicting how Archaeopteryx lithographica is believed to appear in life.

    †Ornithopods

    Ornithopoda of the Kimmeridgian
    Taxa Presence Location Description Images
    Kimmeridgian to Tithonian Wyoming, USA Camptosaurus could be more than 7.9 meters long (26 ft), and 2.0 meters tall (6.7 ft) at the hips. It had heavy bodies but, as well as walking on four legs (quadrupedal), they could rear up to walk on two legs (bipedal). This genus is probably closely related to the ancestor of the later iguanodontid and hadrosaurid dinosaurs. It probably ate cycads with its parrot-like beak.
    Othnielosaurus

    †Plesiosaurs

    Plesiosaurs of the Kimmeridgian
    Taxa Presence Location Description Images

    †Sauropods

    †Sauropods of the Kimmeridgian
    Taxa Presence Location Description Images
    • Amphicoelias
    Europasaurus holgeri
    • Europasaurus holgeri

    †Stegosaurs

    Stegosaurs of the Kimmeridgian
    Taxa Presence Location Description Images
    England and France A large stegosaurid
    Dacentrurus
    Stegosaurus
    Upper Shaximiao Formation, Sichuan, China Had relatively small dorsal plates and greatly enlarged shoulder spines, twice the length of the shoulder blades. Estimated to have been about 4 metres long.
    Morrison Formation, Wyoming, USA Had alternating plates on its back and four spikes on its tail. Appears more closely related to Dacentrurus than Stegosaurus.
    Tanzania A 4 meter long stegosaurian with spikes on its flanks. The length of the thigh bone compared with the rest of the leg indicates that Kentrosaurus was a slow and inactive dinosaur.
    Loe-ein Formation, Tibet, China The fragmentary condition of the only known skeleton places doubt on the validity of this genus
    Kimmeridgian to Early Tithonian Morrison Formation, Colorado, Utah, Wyoming, USA Averaging around 9 metres (30 ft) long and 4 metres (14 ft) tall, the quadrupedal Stegosaurus is one of the most easily identifiable dinosaurs, due to the distinctive double row of kite-shaped plates rising vertically along its arched back and the two pairs of long spikes extending horizontally near the end of its tail.

    †Thalattosuchians

    Thalattosuchians of the Kimmeridgian
    Taxa Presence Location Description Images
    D. maximus
    		 Germany type species of the genus, is known from Western Europe (England, France, Switzerland and Germany) of the Late Jurassic (Late Kimmeridgian-Early Tithonian).
    Dakosaurus, a marine crocodilian.
    C. suevicus
    		 Germany A relatively small metriorhynchid genus.
    1. M. geoffroyii
    2. M. hastifer
    		 England, France and Switzerland An opportunistic carnivore that fed on fish, belemnites and other marine animals and possible carrion. Metriorhynchus grew to an average adult length of 3 meters (9.6 feet).
    Metriorhynchus, a marine crocodilian.

    †Theropods (non-avian)

    †Non-avian theropods of the Kimmeridgian
    Taxa Presence Location Description Images
    • Aviatyrannis jurassica
    		 Guimarota Mine, Portugal Small 5 kg tyrannosauroid. Avityrannis along with Stokesosaurus represents the oldest known tyrannosauroids.
    Ceratosaurus
    Elaphrosaurus
    Torvosaurus
    • Coelurus fragilis
    		 Morrison Formation, Wyoming Small theropod about 2 metres in length
    • Elaphrosaurus bambergi
    		 Tendaguru Beds, Tanzania Probably a ceratosaur about 6 meters long
    • Stokesosaurus clevelandi
    • Torvosaurus tanneri
    • Torvosaurus gurneyi

    Nautiloids

    Nautiloids of the Kimmeridgian
    Taxa Presence Location Description Images
    • Somalinautilus
    An illustration of a variety of fossil nautiloids.

    †Ammonites

    Ammonites of the Kimmeridgian
    Taxa Presence Location Description Images
    • Lithacosphinctes
    Lithacosphinctes achilles.

    †Belemnites

    Belemnites of the Kimmeridgian
    Taxa Presence Location Description Images
    Small belemnite fossils

    Palaeontological sites

    References

    Notes

    1. ↑ For a detailed version of the ICS' timescale, see Gradstein et al. (2004)
    2. ↑ INTERNATIONAL SUBCOMMISSION ON JURASSIC STRATIGRAPHY, Newsletter 31, Edited by Nicol Morton and Paul Bown, August 2004

    Literature

    External links

    Jurassic Period
    Lower/Early Jurassic Middle Jurassic Upper/Late Jurassic
    Hettangian | Sinemurian
    Pliensbachian | Toarcian    		 Aalenian | Bajocian
    Bathonian | Callovian    		 Oxfordian | Kimmeridgian
    Tithonian
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