Toarcian

System/
Period		 Series/
Epoch		 Stage/
Age		 Age (Ma)
Cretaceous Lower/
Early		 Berriasian younger
Jurassic Upper/
Late		 Tithonian ~145.0 152.1
Kimmeridgian 152.1 157.3
Oxfordian 157.3 163.5
Middle Callovian 163.5 166.1
Bathonian 166.1 168.3
Bajocian 168.3 170.3
Aalenian 170.3 174.1
Lower/
Early		 Toarcian 174.1 182.7
Pliensbachian 182.7 190.8
Sinemurian 190.8 199.3
Hettangian 199.3 201.3
Triassic Upper/
Late		 Rhaetian older
Subdivision of the Jurassic system
according to the ICS, as of 2017.[1]

The Toarcian is, in the ICS' geologic timescale, an age or stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma (million years ago) and 174.1 Ma.[2] It follows the Pliensbachian and is followed by the Aalenian.[3]

The Toarcian age began with the Toarcian turnover, the extinction event that sets its fossil faunas apart from the previous Pliensbachian age.

Stratigraphic definitions

The Toarcian takes its name from the city of Thouars, just south of Saumur in the Loire Valley of France. The stage was introduced by French palaeontologist Alcide d'Orbigny in 1842, after examining rock strata of this age in a quarry near Thouars.

In Europe this period is represented by the upper part of the Lias.

The base of the Toarcian is defined as the place in the stratigraphic record where the ammonite genus Eodactylites first appears. A global reference profile (a GSSP) for the base is located at Peniche, Portugal. The top of the stage is at the first appearance of ammonite genus Leioceras.

In the Tethys domain, the Toarcian contains the following ammonite biozones:

Palaeontology

Amphibians

Amphibians of the Toarcian
Taxa Presence Location Description Images
Pliensbachian-Toarcian Evergreen Formation, Australia

Ichthyosaurs

Ichthyosaurs of the Toarcian
Taxa Presence Location Description Images
Europe
Hettangian to Toarcian All over Europe An ichthyosaur that exceeded 12 metres (39 ft) in length

†Ornithischians

Ornithischians of the Toarcian
Taxa Presence Location Description Images
Germany Armored dinosaur known from a skull and partial postcranial remains, although only the skull is known well. Armor includes conical scutes and tall, spiny elements.

†Plesiosaurs

Plesiosauria of the Toarcian
Taxa Presence Location Description Images
Tournemire, Aveyron, France A plesiosaur similar to Elasmosaurus; fossils consist of a single but nearly complete skeleton of an animal approximately 4 meters (13 ft) long
Rhomaleosaurus
Toarcian Alum Shale, Yorkshire, England A genus of sauropterygian carnivorous reptile belonging to the pliosaur superfamily, it was about 7m long.
Toarcian Württemberg, Germany A large (about 3 to 5 meters long), marine sauropterygian reptile, it was distinguished by its small head, long and slender neck, broad turtle like body, a short tail, and two pairs of large, elongated paddles

†Sauropods

Sauropoda of the Toarcian
Taxa Presence Location Description Images
Maharastra, India Reached a length of about 18 metres (60 feet), and weighed about 48 tones (53 tons). Its height to the hip was approximately 5.5 metres (18 feet)
Barapasaurus
Disputed Central Queensland, Australia Estimated to have been about 12–15 metres long. Has been compared to Shunosaurus, based on similar general age, but without justification.
Toarcian Ouarzazate province, Morocco Small primitive sauropod, about 9 metres long. Member of Vulcanodontidae family.[4]

†Thalattosuchians

Thalattosuchia of the Toarcian
Taxa Presence Location Description Images
Pelagosaurus
Platysuchus
Steneosaurus
Somerset, England; France; Germany
Germany
Germany; France; England; Morocco; and Switzerland

References

  1. ↑ http://www.stratigraphy.org/index.php/ics-chart-timescale
  2. ↑ Benton, Michael J. (2012). Prehistoric Life. Edinburgh, Scotland: Dorling Kindersley. pp. 44–45. ISBN 978-0-7566-9910-9.
  3. ↑ For a detailed geologic timescale see Gradstein et al. (2004)
  4. ↑ Allain, Ronan; Najat Aquesbi; Jean Dejax; Christian Meyer; Michel Monbaron; Christian Montenat; Philippe Richir; Mohammed Rochdy; Dale Russell; Philippe Taquet (2004). "A basal sauropod dinosaur from the Early Jurassic of Morocco". Comptes Rendus Palevol. 3 (3): 199–208. doi:10.1016/j.crpv.2004.03.001. ISSN 1631-0683.

Sources

  • Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.
  • d´Orbigny, A.C.V.M.D.; 1842: Paléontologie française. 1. Terrains oolitiques ou jurassiques, Bertrand, Paris. (in French)
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