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 2020[1]

The Toarcian is, in the ICS' geologic timescale, an age and 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 definitionsEdit

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:

PalaeontologyEdit

AmphibiansEdit

Amphibians of the Toarcian
Taxa Presence Location Description Images
Pliensbachian-Toarcian Evergreen Formation, Australia A brachyopoid stereospondyl.
Upper Toarcian Cañadón Asfalto Formation, Chubut, Argentina An extinct genus of archaeobatrachian frog and a member of the extant family Ascaphidae. One of the oldest true frogs discovered.

†IchthyosaursEdit

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

†OrnithischiansEdit

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.

†PlesiosaursEdit

Plesiosauria of the Toarcian
Taxa Presence Location Description Images
Ziliujing Formation, China A pliosauroid, possibly a rhomaleosaurid.
England and Germany A basal pliosaurid.
Posidonia Shale formation, Germany A basal plesiosauroid.
Portugal A basal plesiosauroid, likely a close relative of Microcleidus.
Holzmaden,southwestern Germany A rhomaleosaurid. Its skull has a length of 37 cm, and the animal was about 3.35 m (11.0 ft) in length.
  • Microcleidus
    • M. homalospondylus
    • M. macropterus
    • M. tournemirensis
    • M. melusinae
Tournemire, Aveyron, France A plesiosaur similar to Elasmosaurus, measuring around 3 meters in length. A fossil of a single but nearly complete skeleton of an animal approximately 4 meters (13 ft) long, originally described as Occitanosaurus tournemirensis, is now considered as a species of Microcleidus..
Posidonia Shale formation, Germany A basal plesiosauroid, possibly a close relative of Cryptoclidus.
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), microcleidid, 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
England A genus of rhomaleosaurid pliosaur.

†SauropodsEdit

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)
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]

†ThalattosuchiansEdit

Thalattosuchia of the Toarcian
Taxa Presence Location Description Images
England; and Germany A teleosaurid.
China A teleosaurid.
Somerset, England; France; Germany Traditionally placed in Teleosauridae, it might a basal member of Metriorhynchoidea instead.
Germany A teleosaurid.
Germany; France; England; Morocco; and Switzerland A teleosaurid.

TheropodsEdit

Theropods of the Aalenian
Taxa Presence Location Description Images

Asfaltovenator

Toarcian-Bajocian Cañadón Asfalto Basin, Patagonia, Argentina A large basal carnosaur. The unique combination of characteristics seen in Asfaltovenator may indicate megalosauroids and allosauroids shared a common ancestor not shared with Coelurosauria.

Berberosaurus

Middle Toarcian Azilal Formation in the High Atlas of Toundoute, Ouarzazate, Morocco. A primitive, medium sized neotheropod, possibly a dilophosaurid but most likely a basal ceratosaur.
 
Berberosaurus.

Condorraptor

Aalenian-Bajocian Cañadón Asfalto Basin, Patagonia, Argentina It was among the earliest large South American theropods.
 
Condorraptor.

Magnosaurus

Aalenian-Bajocian Dorset, England Magnosaurus was one of the first megalosaurids to evolve.
 
Magnosaurus.

ReferencesEdit

  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" (PDF). Comptes Rendus Palevol. 3 (3): 199–208. doi:10.1016/j.crpv.2004.03.001. ISSN 1631-0683.

SourcesEdit

  • 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)

External linksEdit