Turonian

The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded by the Cenomanian stage and underlies the Coniacian stage.^[1]

At the beginning of the Turonian an anoxic event took place which is called the Cenomanian-Turonian boundary event or the "Bonarelli Event".

Stratigraphic definition

Lithographic limestone from the Gerofit Formation (Turonian) north of Makhtesh Ramon, southern Israel; a variety of Jerusalem stone (meleke).

The Turonian (French: Turonien) was definied by the French paleontologist Alcide d'Orbigny (1802–1857) in 1842. Orbigny named it after the French city of Tours in the region of Touraine (department Indre-et-Loire), which is the original type locality.

The base of the Turonian stage is defined as the place where the ammonite species Wutinoceras devonense first appears in the stratigraphic column. The official reference profile (the GSSP) for the base of the Turonian is located in the Rock Canyon anticline near Pueblo, Colorado (USA, coordinates: 38° 16' 56" N, 104° 43' 39" W).^[2]

The top of the Turonian stage (the base of the Coniacian) is defined as the place in the stratigraphic column where the inoceramid bivalve species Cremnoceramus rotundatus first appears.

Subdivision

The Turonian is sometimes subdivided in Lower/Early, Middle and Upper/Late substages or subages. In the Tethys domain, it contains the following ammonite biozones:

• zone of Subprionocyclus neptuni (in the Upper Turonian)
• zone of Collignoniceras woollgari (in the Middle Turonian)
• zone of Mammites nodosoides
• zone of Wutinoceras coloradoense or Wutinoceras devonense (last two both in the Lower Turonian)

Other important index fossils are species of the inoceramid genus Inoceramus (I. schloenbachi, I. lamarcki and I. labiatus). Inoceramids are bivalve Mollusca related to today's mussels.

Palaeontology

†Ankylosaurs

Birds (avian theropods)

Aves of the Turonian
Taxa	Presence	Location	Description	Images
Catenoleimus		Bissekty Formation, Uzbekistan	A mid-sized enantiornithine, perhaps 20–25 cm long in life	Ichthyornis
Explorornis		Bissekty Formation, Uzbekistan
Ichthyornis	Turonian - Campanian	Alberta and Saskatchewan, Canada; Alabama, Kansas, New Mexico and Texas, USA; Argentina; Central Asia	The Cretaceous ecological equivalent of modern seabirds such as gulls, petrels, and skimmers. At 60 cm (2 ft), it was the size of a gull. Although the wings and breastbone are very modern in appearance (suggesting strong flight ability), the jaws retained numerous small, sharp teeth

†Ceratopsians

Ceratopsia of the Turonian
Taxa	Presence	Location	Description	Images
Zuniceratops		Moreno Hill Formation, New Mexico, USA	The earliest-known ceratopsian to have eyebrow horns and the oldest-known ceratopsian from North America, appears to have been roughly 3 to 3.5 meters long (10–11 ft) and 1 meter (3 ft) tall at the hips.	Zuniceratops

Crocodylomorphs

Crocodylomorpha of the Turonian
Taxa	Presence	Location	Description	Images
Baurusuchus				Baurusuchus
Montealtosuchus	Turonian to Santonian	Adamantina Formation, São Paulo, Brazil	A terrestrial Peirosaurid
Stratiosuchus

Mammals

†Ornithopods

Ornithopoda of the Turonian
Taxa	Presence	Location	Description	Images
Bactrosaurus	Turonian to Coniacian	Gobi Desert, Mongolia and China	Would have been 6 m (20 ft) long[1] and 2 m (7 ft) high when in the quadrupedal stance, and weighed 1100 – 1500 kg (2400 - 3300 lb). Like many hadrosaurs, it could switch between bipedal and quadrupedal stances, but unusually it had large spines protruding from the vertebrae.	Bactrosaurus
Macrogryphosaurus	Turonian to early Coniacian	Portezuelo Formation, Argentina	A genus of basal iguanodont, a large bipedal herbivor
Notohypsilophodon	Cenomanian-Turonian	Bajo Barreal Formation, Chubut, Argentina	A hypsilophodontid or other basal ornithopod, Notohypsilophodon would have been a bipedal herbivore. Its size has not been estimated
Shuangmiaosaurus	Cenomanian-Turonian	China	A poorly known iguanodont

†Plesiosaurs

Plesiosauria of the Turonian
Taxa	Presence	Location	Description	Images
Libonectes		Britton Formation (Cedar Hill), Texas, USA	A 7–14 m (23–47 ft) long creature, was very similar to the related Elasmosaurus. It had a compact body with a short tail and large flippers. Its small skull had long, forward-facing teeth ideal for catching slippery fish and squid that came together outside of its mouth when the mouth was closed, and was placed atop a very long neck.	Libonectes Polyptychodon Thililua
Manemergus		Morocco	A genus of polycotylid plesiosaur
Polyptychodon hudsoni		Texas, USA
Thililua		High Atlas, Morocco	A genus of polycotylid plesiosaur, the estimated total length of Thililua is 5.5 to 6 metres.

Squamats

†Theropods (non-avian)

Theropods of the Turonian
Taxa	Presence	Location	Description	Images
Bayosaurus				Giganotosaurus Nothronychus
Giganotosaurus		Rio Limay, Argentina
Nothronychus
Urbacodon

References

Notes

1. ↑ See Gradstein et al. (2004) for a detailed description of the ICS' timescale
2. ↑ The GSSP was established by Kennedy et al. (2005)

Literature

• Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.
• Kennedy, W.J.; Walaszczyk, I. & Cobban, W.A.; 2005: The Global Boundary Stratotype Section and Point for the base of the Turonian Stage of the Cretaceous: Pueblo, Colorado, U.S.A., Episodes 28(2): pp 93–104.

External links

• GeoWhen Database - Turonian
• Late Cretaceous timescale, at the website of the subcommission for stratigraphic information of the ICS
• Stratigraphic charts of the Cretaceous: and , at the website of Norges Network of offshore records of geology and stratigraphy
• Turonian Microfossils: 48 images of Foraminifera