Bajocian

In the geologic timescale, the Bajocian is an age or stage in the Middle Jurassic. It lasted from approximately 170.3 Ma to around 168.3 Ma (million years ago). The Bajocian age succeeds the Aalenian age and precedes the Bathonian age.^[1]

Stratigraphic definitions

The Bajocian stage takes its name from the Latin name (Bajocae) of the town of Bayeux, in the region of Normandy in France. The stage was named and introduced in scientific literature by French palaeontologist Alcide d'Orbigny in 1842.

The base of the Bajocian stage is defined as the place in the stratigraphic column where fossils of the ammonite genus Hyperlioceras first appear. A global reference profile (a GSSP) for the base is located at Murtinheira, close to Cabo Mondego in Portugal.^[2] The top of the Bajocian (the base of the Bathonian) is at the first appearance of ammonite species Parkinsonia convergens.

Subdivision

The Bajocian is often divided into Lower/Early and Upper/Late subages or substages.

In the Tethys domain, the Bajocian contains seven ammonite biozones:

• zone of Parkinsonia parkinsoni
• zone of Garantiana garantiana
• zone of Strenoceras niortense
• zone of Stephanoceras humphriesianum
• zone of Sonninia propinquans
• zone of Witchellia laeviuscula
• zone of Hyperlioceras discites

Palaeontology

†Thalattosuchians

Thalattosuchians of the Bajocian
Taxa	Presence	Location	Description	Images
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.	A life restoration of a Metriorhynchus species.
Steneosaurus
Teleosaurus
Teleidosaurus		Normandie, France	The most plesiomorphic known metriorhynchid.	Teleidosaurus

Dinosauria

Rhoetosaurus, Ozraptor, Yunnanosaurus, Cetiosauriscus, Xiaosaurus

†Plesiosauria

• Simolestes keileni
• Maresaurus coccai

†Ammonitida

Ammonitids of the Bajocian
Taxa	Presence[3]	Location	Description	Images
Alfeldites	Confirmed.		The only known species in this Alaskan genus. Abbasites is believed to be ancestral to the ammonite family Otoitidae.	Life restorations of two different ammonite genera.
Apsorroceras	Confirmed.
Asphinctites	Confirmed.
Asthenoceras	Confirmed.
Bigotites	Confirmed.
Bradfordia	Confirmed.
Cadomites	Confirmed.
Cadomoceras	Confirmed.
Caumontisphinctes	Confirmed.
Chondroceras	Confirmed.
Cleistosphinctes	Confirmed.
Cranocephalites	Confirmed.
Darellia	Confirmed.
Dimorphinites	Confirmed.
Diplesioceras	Confirmed.
Docidoceras	Confirmed.
Dorsetensia	Confirmed.
Durotrigensia	Confirmed.
Duashnoceras	Confirmed.
Emileia	Confirmed.
Eocephalites	Confirmed.
Epistrenoceras	Confirmed.
Ermoceras	Confirmed.
Euaptetoceras	Confirmed.
Eudmetoceras	Confirmed.
Euhoploceras	Confirmed.
Fissilobiceras	Confirmed.
Fontannesia	Confirmed.
Frogdenites	Confirmed.
Garantiana	Confirmed.
Guhsania	Confirmed.
Graphoceras	Confirmed.
Haplopleuroceras	Confirmed.
Hebetoxyites	Confirmed.
Hlawiceras	Confirmed.
Hyperlioceras	Confirmed.
Kosmermoceras	Confirmed.
Kumatostephanus	Confirmed.
Labyrinthoceras	Confirmed.
Leptosphinctes	Confirmed.
Lissoceras	Confirmed.
Lupherites	Confirmed.
Magharina	Confirmed.
Megasphaeroceras	Confirmed.
Metrolytoceras	Confirmed.
Nannolytoceras	Confirmed.
Newmarracarroceras	Confirmed.
Normannites	Confirmed.
Oecoptychius	Confirmed.
Oecotraustes	Confirmed.
Okribites	Confirmed.
Oppelia	Confirmed.
Orthogarantiana	Confirmed.
Otoites	Confirmed.
Oxycerites	Confirmed.
Padragosiceras	Confirmed.
Parastrenoceras	Confirmed.
Parkinsonia	Confirmed.
Phaulostephanus	Confirmed.
Poecilomorphus	Confirmed.
Praebigotites	Confirmed.
Praeparkinsonia	Confirmed.
Praestrigites	Confirmed.
Procerites	Confirmed.
Prorsisphinctes	Confirmed.
Protoecotrausites	Confirmed.
Pseudogarantiana	Confirmed.
Pseudotoites	Confirmed.
Reynesella	Confirmed.
Shirbuirnia	Confirmed.
Siemiradzkia	Confirmed.
Skirroceras	Confirmed.
Skolekostephanus	Confirmed.
Sohlites	Confirmed.
Sonninia	Confirmed.
Sphaeroceras	Confirmed.
Spinammatoceras	Confirmed.
Spiroceras	Confirmed.
Stegoxyites	Confirmed.
Stemmatoceras	Confirmed.
Strenoceras	Confirmed.
Strigoceras	Confirmed.
Subcollina	Confirmed.
Telermoceras	Confirmed.
Teloceras	Confirmed.
Thamboceras	Confirmed.
Toxamblyites	Confirmed.
Toxolioceras	Confirmed.
Trilobiticeras	Confirmed.
Trimarginia	Confirmed.
Tugurites	Confirmed.
Vermisphinctes	Confirmed.
Witchellia	Confirmed.
Zemistephanus	Confirmed.
Zurcheria	Confirmed.

†Belemnites

Belemnites of the Bajocian
Taxa	Presence[3]	Location	Description	Images
Belemnitina	Confirmed.			Belemnites
Hibolites	Confirmed.
Holcobelus	Confirmed.
Produvalia	Confirmed.
Sachsibelus	Confirmed.

Nautiloids

Nautiloids of the Bajocian
Taxa	Presence[3]	Location	Description	Images
Ophionautilus	Confirmed.			An illustration of a variety of fossil nautiloids.
Somalinautilus	Confirmed.

References

Notes

Literature

• Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.
• Alcide d´Orbigny; 1842: Paléontologie française. 1. Terrains oolitiques ou jurassiques, 642 pp., Bertrand, Paris.
• Pavia, G. & Enay, R.; 1997: Definition of the Aalenian-Bajocian Stage boundary, Episodes, 20(1): pp 16–22.
• Sepkoski, J.; 2002: A compendium of fossil marine animal genera (entry on cephalopoda), Bulletin of American Paleontology 364, p 560.

External links

Wikisource has the text of the 1911 Encyclopædia Britannica article Bajocian.

• GeoWhen Database - Bajocian
• Jurassic-Cretaceous and Lower Jurassic timescales, 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