| Toarcian | |
|---|---|
| 182.7 ± 0.7 – 174.1 ± 1.0 Ma | |
| Chronology | |
| Etymology | |
| Name formality | Formal |
| Usage information | |
| Celestial body | Earth |
| Regional usage | Global (ICS) |
| Time scale(s) used | ICS Time Scale |
| Definition | |
| Chronological unit | Age |
| Stratigraphic unit | Stage |
| Time span formality | Formal |
| Lower boundary definition | Peniche, Portugal |
| Lower boundary GSSP | FAD of the Ammonite D. (E.) simplex 39°22′15″N 9°23′07″W / 39.3708°N 9.3853°W |
| GSSP ratified | 2014[2] |
| Upper boundary definition | FAD of the Ammonites Leioceras opalinum and Leioceras lineatum |
| Upper boundary GSSP | Fuentelsaz, Spain 41°10′15″N 1°50′00″W / 41.1708°N 1.8333°W |
| GSSP ratified | 2000[3] |
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.[4] It follows the Pliensbachian and is followed by the Aalenian.[5]
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:
- zone of Pleydellia aalensis
- zone of Dumortieria pseudoradiosa
- zone of Phlyseogrammoceras dispansum
- zone of Grammoceras thouarcense
- zone of Haugia variabilis
- zone of Hildoceras bifrons
- zone of Harpoceras serpentinum
- zone of Dactylioceras tenuicostatum
Palaeontology
Amphibians
| Amphibians of the Toarcian | ||||
|---|---|---|---|---|
| Taxa | Presence | Location | Description | Images |
| Pliensbachian-Toarcian | Evergreen Formation, Australia | A brachyopoid stereospondyl. | ) Siderops ) Notobatrachus |
| 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. | |
†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 |
| Ciechocinek Formation, 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 |
| Ziliujing Formation, China | A pliosauroid, possibly a rhomaleosaurid. | ) Bishanopliosaurus ) Hydrorion ) Meyerasaurus ) Seeleysaurus | |
| 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. | ||
| 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. | ||
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†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) | |||
| 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.[6] | ||
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†Thalattosuchians
| Thalattosuchia of the Toarcian | ||||
|---|---|---|---|---|
| Taxa | Presence | Location | Description | Images |
| Early Toarcian | Whitby Mudstone Formation of England, and Germany | A machimosaurid teleosauroid. | ) Pelagosaurus ) Platysuchus ) Macrospondylus |
| Early Toarcian | Whitby Mudstone Formation of England, and Germany | A teleosaurid teleosauroid. | |
| China | A basal metriorhynchoid. | ||
| Early Toarcian | England, France, and Germany | A basal metriorhynchoid. | |
| Early Toarcian | Germany, and Luxembourg | A teleosaurid teleosauroid in the subfamily Teleosaurinae. | |
| Early Toarcian | Whitby Mudstone Formation of England, and Luxembourg | A basal teleosauroid. | |
Theropods
| 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. | |
| 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. | ||
| Aalenian-Bajocian | Cañadón Asfalto Basin, Patagonia, Argentina | It was among the earliest large South American theropods. | ||
| Aalenian-Bajocian | Dorset, England | Magnosaurus was one of the first megalosaurids to evolve. | ||
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References
- ^ "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy.
- ^ da Rocha, Rogério Bordalo; Mattioli, Emanuela; Duarte, Luís Vítor; Pittet, Bernard; Elmi, Serge; Mouterde, René; Cabral, Maria Cristina; Comas-Rengifo, Maria José; Gómez, Juan José; Goy, António; Hesselbo, Stephen P.; Jenkyns, Hugh C.; Littler, Kate; Mailliot, Samuel; Veiga de Oliveira, Luiz Carlos; Osete, Maria Luisa; Nicola, Perilli; Pinto, Susana; Ruget, Christiane; Suan, Guillaume (September 2016). "Base of the Toarcian Stage of the Lower Jurassic defined by the Global Boundary Stratotype Section and Point (GSSP) at the Peniche section (Portugal)". Episodes. 39 (3): 460–481. doi:10.18814/epiiugs/2016/v39i3/99741. Retrieved 29 August 2020.
- ^ Cresta, S.; Goy, A.; Arias, C.; Barrón, E.; Bernad, J.; Canales, M.; García-Joral, F.; García-Romero, E; Gialanella, P.; Gómez, J.; González, J.; Herrero, C.; Martínez2, G.; Osete, M.; Perilli, N.; Villalaín, J. (September 2001). "The Global Boundary Stratotype Section and Point (GSSP) of the Toarcian-Aalenian Boundary (Lower-Middle Jurassic)" (PDF). Episodes. 24: 166–175. Retrieved 13 December 2020.
- ^ Benton, Michael J. (2012). Prehistoric Life. Edinburgh, Scotland: Dorling Kindersley. pp. 44–45. ISBN 978-0-7566-9910-9.
- ^ For a detailed geologic timescale see Gradstein et al. (2004)
- ^ 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.
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)
External links
- GeoWhen Database - Toarcian
- Lower Jurassic timescale, at the website of the subcommission for stratigraphic information of the ICS
- Stratigraphic chart of the Lower Jurassic, at the website of Norges Network of offshore records of geology and stratigraphy