Kimmeridgian

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:

• zone of Hybonoticeras beckeri
• zone of Aulacostephanus eudoxus
• zone of Aspidoceras acanthicum
• zone of Crussoliceras divisum
• zone of Ataxioceras hypselocyclum
• zone of Sutneria platynota
• zone of Idoceras planula

Palaeontology

†Ankylosaurs

Ankylosaurs of the Kimmeridgian
Taxa	Presence	Location	Description	Images
Gargoyleosaurus		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 Mymoorapelta maysi		Morrison Formation, Colorado, USA	A poorly known early ankylosaurian.

Birds

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

†Ornithopods

Ornithopoda of the Kimmeridgian
Taxa	Presence	Location	Description	Images
Camptosaurus	Kimmeridgian to ?Berriasian	Wyoming, USA; England; France	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
Drinker
Dryosaurus
Othnielia
Othnielosaurus
Phyllodon

†Plesiosaurs

Plesiosaurs of the Kimmeridgian
Taxa	Presence	Location	Description	Images
Liopleurodon				Liopleurodon
Pliosaurus
Colymbosaurus
Kimmerosaurus

†Sauropods

†Sauropods of the Kimmeridgian
Taxa	Presence	Location	Description	Images
Amphicoelias Amphicoelias fragillimus?				Europasaurus holgeri
Apatosaurus
Brachiosaurus
Camarasaurus
Dicraeosaurus
Diplodocus
Dystrophaeus
Eobrontosaurus
Europasaurus Europasaurus holgeri

†Stegosaurs

Stegosaurs of the Kimmeridgian
Taxa	Presence	Location	Description	Images
Dacentrurus		England, France, Spain, Portugal	A large stegosaurid	Dacentrurus Stegosaurus
Gigantspinosaurus		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.
Hesperosaurus		Morrison Formation, Wyoming, USA	Had alternating plates on its back and four spikes on its tail. Appears more closely related to Dacentrurus than Stegosaurus.
Kentrosaurus		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.
Monkonosaurus		Loe-ein Formation, Tibet, China	The fragmentary condition of the only known skeleton places doubt on the validity of this genus
Stegosaurus	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
Dakosaurus 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.
Geosaurus G. suevicus		Germany	A relatively small metriorhynchid genus. No known species of Geosaurus attained lengths in excess of 3 meters (10 feet).	Geosaurus, a marine crocodilian.
Machimosaurus
Metriorhynchus M. acutus M. geoffroyii M. hastifer M. palpebrosus		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.
Steneosaurus

†Theropods (non-avian)

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

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
Produvalia				Small belemnite fossils

Palaeontological sites

• Guimarota

References

Notes

Literature

• Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.
• Thurmann, J.; 1832: Sur Les Soulèvemens Jurassiques Du Porrentruy: Description Géognostique de la Série Jurassique et Théorie Orographique du Soulèvement, Mémoires de la Société d'histoire naturelle de Strasbourg 1: pp 1–84, F. G. Levrault, Paris.(French)

External links

• GeoWhen Database - Kimmeridgian
• Jurassic-Cretaceous timescale, at the website of the subcommission for stratigraphic information of the ICS
• Stratigraphic chart of the Upper Jurassic, at the website of Norges Network of offshore records of geology and stratigraphy