Kimmeridgian

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The Kimmeridgian is a stage of the Late Jurassic Epoch. It spans the time between 155.7 ± 4 Ma and 150.8 ± 4 Ma (million years ago). The Kimmeridgian stage follows the Oxfordian stage and precedes the Tithonian stage.

The stage takes its name from the village of Kimmeridge on the Dorset coast, England where the exposure is at its greatest extent. The beach at Kimmeridge Bay is a good place for looking for fossils — there are specimens on the beach washed in by the tide.

The Kimmeridge Clay formation is the source for about 95% of the petroleum in the North Sea.

[edit] Usage of the term

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 stage (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, although Kimmeridge-Tithonian are now the agreed terms globally^[1]

[edit] Vertebrate Fauna

[edit] Ankylosaurs

Birds 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.

[edit] 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.

[edit] 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.	Camptosaurus Dryosaurus Othnielosaurus
Drinker
Dryosaurus
Othnielia
Othnielosaurus
Phyllodon

[edit] Plesiosaurs

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

[edit] Sauropods

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

[edit] Stegosaurs

Stegosaurs of the Kimmeridgian
Taxa	Presence	Location	Description	Images
Dacentrurus		England, France, Spain, Portugal	A large stegosaurid	Dacentrurus Kentrosaurus 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.

[edit] 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 and France	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

[edit] Theropods

[edit] Invertebrate Fauna

[edit] Nautiloids

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

[edit] Belemnites

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

[edit] Environment

Ammonites such as this Jurassic period ammonite were common during the latest environment of the Kimmeridgian stage.

The variation of fauna during the Kimmeridgian stage indicates the existence of two distinct environments, the first being a being a shallow and agitated layer abundant in pebbles and fossils and the second following environment being a calm and deep layer marked by an absence of pebbles and by an abundance of pelagic organisms, such as Ammonites.

[edit] Localities

• Guimarota

[edit] References

1. ^ SUBCOMMISSION ON JURASSIC STRATIGRAPHY, Newsletter 31, Edited by Nicol Morton and Paul Bown, August 2004

• GeoWhen Database - Kimmeridgian