Oxfordian (stage)

The Oxfordian is, in the ICS' geologic timescale, the earliest age of the Late Jurassic epoch, or the lowest stage of the Upper Jurassic series. It spans the time between 163.5 ± 4 Ma and 157.3 ± 4 Ma (million years ago). The Oxfordian is preceded by the Callovian and is followed by the Kimmeridgian.^[1]

Stratigraphic definitions

Cyclically alternating limestone (light, more competent) and marl/clay layers of Oxfordian age at Péry-Reuchenette, near Tavannes, Jura Mountains, Switzerland.

The Oxfordian stage was introduced into scientific writing by Alexandre Brongniart in 1827. The stage takes its name from the city of Oxford in England.

The base of the Oxfordian stage is defined as the point in the stratigraphic record where the ammonite species Brightia thuouxensis first appears. A global reference profile for the base (a GSSP) had in 2009 not yet been assigned. The top of the Oxfordian stage (the base of the Kimmeridgian) is at the first appearance of ammonite species Pictonia baylei.

In the Tethys domain, the Oxfordian contains six ammonite biozones:

• zone of Epipeltoceras bimammatum
• zone of Perishinctes bifurcatus
• zone of Gregoryceras transversarium
• zone of Perisphinctes plicatilis
• zone of Cardioceras cordatum
• zone of Quenstedtoceras mariae

Palaeontology

†Ornithischians

Ornithischians of the Oxfordian
Taxa	Presence	Location	Description	Images
Chaoyangsaurus	Oxfordian? Tithonian?	Chaoyang, Liaoning, China	A marginocephalian dinosaur from the Late Jurassic of China, belonged to the Ceratopsia, a group of primarily herbivorous dinosaurs with parrot-like beaks	Chaoyangsaurus Chialingosaurus Chungkingosaurus Dacentrurus Tuojiangosaurus Yinlong
Chialingosaurus		Upper Shaximiao Formation, Sichuan, China	A genus of stegosaur similar to Kentrosaurus
Chungkingosaurus		Upper Shaximiao Formation, Sichuan, China	One of the smallest of the stegosaurids at 3–4 metres long (10–13 ft), Chungkingosaurus had at least five spikes on its thagomizer. It had a rather high and narrow skull and large, thick bony plates.
Dacentrurus		England, France, Spain, Portugal	A large stegosaurid
Gongbusaurus		Dashanpu Formation, Sichuan, China	By extrapolation from the remains of possible species and other basal ornithopods, it was a herbivorous bipedal animal around 1.3 to 1.5 meters long (4.3 to 4.9 ft). It would have been a strong runner
Jiangjunosaurus		Junggar Basin, Xinjiang, China	A genus of stegosaurid
Tuojiangosaurus		Upper Shaximiao Formation, Sichuan, China	The best understood of the Chinese stegosaurs. It was around 7.0 meters (23 ft) long and 2 meters (7 ft) high, with a postulated weight of around 4 metric tons (4.4 short tons).
Yinlong		Shishugou Formation, Xinjiang, China	A small, primarily bipedal herbivore, approximately 1.2 meters (4 ft) long, the oldest and most primitive ceratopsian known to science.

†Thalattosuchians

Thalattosuchians of the Oxfordian
Taxa	Presence	Location	Description	Images
Aggiosaurus				Geosaurus Metriorhynchus, a marine crocodilian.
Geosaurus
Metriorhynchus			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), although some individuals may have reached lengths rivaling those of large nile crocodiles.
Steneosaurus

Theropods

Theropoda of the Oxfordian
Taxa	Presence	Location	Description	Images
Yangchuanosaurus		Upper Shaximiao Formation, Sichuan, China	Yangchuanosaurus shangyouensis reached about 7 meters long (23 ft) with a skull around 80 cm long (32 in). Its relative Y. magnus grew larger still: up to 10 meters long (33 ft) with a skull up to 1 metre (3 ft) in length. There was a bony knob on its nose and multiple hornlets and ridges, similar to Ceratosaurus. It had a massive tail that was about half its length.
Monolophosaurus		Upper Shaximiao Formation, China	Monolophosaurus was a medium-sized predator that grew to at least 5.7 meters (19 ft) long. It had an odd, unique crest on its head which ran most of the length of the skull.	Yangchuanosaurus

Cephalopods

Cephalopods of the Oxfordian
Taxa	Presence	Location	Description	Images
Produvalia				Belemnite fossils
Somalinautilus				An illustration of a variety of fossil nautiloids.

References

Notes

Literature

• Brongniart, A.; 1829: Tableau théorique de la succession et de la disposition la plus générale on Europa, des terrains et roches, qui composent l'écorce de la terre, Paris.(French)
• Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.

External links

• GeoWhen Database - Oxfordian
• 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