Toarcian

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.

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]

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

†Sauropods

†Thalattosuchians

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)

External links

Aalenian

The Aalenian ( ) is a subdivision of the Middle Jurassic epoch/series of the geologic timescale that extends from about 174.1 Ma to about 170.3 Ma (million years ago). It was preceded by the Toarcian and succeeded by the Bajocian.

Allkaruen

Allkaruen (meaning "ancient brain") is a genus of rhamphorhynchoid pterosaur from the Early-to-Middle Jurassic Cañadon Asfalto Formation in Argentina. It contains a single species, A. koi.

Amygdalodon

Amygdalodon (; "almond tooth" for its almond shaped teeth) was a genus of basal sauropod from the Middle Jurassic of Argentina.

Brachaelurus

Brachaelurus (blind sharks) is the sole genus of sharks in the family Brachaeluridae in the order Orectolobiformes. Only two species of blind sharks occur, both of which are native to shallow coastal waters up to 110 m (360 ft) deep, off the eastern coast of Australia.They are distinguished by the presence of long barbels, large spiracles, and a groove around the nostrils. They have two dorsal fins, placed close together on the back, and a relatively short tail. Blind sharks have fully functioning eyes, but their name was given to them because when caught by anglers these eyes are closed (probably to protect them).Blind sharks feed on small fish, cuttlefish, sea anemones, and crustaceans. The female retains the eggs in her body until they hatch (ovoviviparity), during which time the embryos feed solely on the egg yolk.

Brachyphyllum

Brachyphyllum is a form genus of fossil coniferous plant foliage. Plants of the genus have been variously assigned to several different conifer groups including Araucariaceae and Cheirolepidiaceae. They are known from around the globe from the Late Carboniferous to the Late Cretaceous periods.

Cetiosauridae

Cetiosauridae is a family of sauropod dinosaurs. While traditionally a wastebasket taxon containing various unrelated species, some recent studies have found that it may represent a natural clade. Additionally, at least one study has suggested that the mamenchisaurids may represent a sub-group of the cetiosaurids, which would be termed Mamenchisaurinae.

Condorchelys

Condorchelys was a genus of stem turtle from Early to Middle Jurassic Cañadon Asfalto Formation of Argentina. Only one species is described, Condorchelys antiqua.

Mamenchisauridae

Mamenchisauridae is a family of sauropod dinosaurs known from the Jurassic and Early Cretaceous of Asia and Africa.

Novialoidea

Novialoidea (meaning "new wings") is an extinct clade of macronychopteran pterosaurs that lived from the latest Early Jurassic to the latest Late Cretaceous (early Toarcian to late Maastrichtian age), their fossils having been found on all continents except Antarctica. It was named by Alexander Wilhelm Armin Kellner in 2003 as a node-based taxon consisting of the last common ancestor of Campylognathoides, Quetzalcoatlus and all its descendants. This name was derived from Latin novus "new", and ala, "wing", in reference to the wing synapomorphies that the members of the clade possess. Unwin (2003) named Lonchognatha in the same issue of the journal that published Novialoidea (Geological Society of London, Special Publications 217) and defined it as Eudimorphodon ranzii, Rhamphorhynchus muensteri, their most recent common ancestor and all its descendants (as a node-based taxon). Under Unwin's and Kellner's phylogenetic analyses (where Eudimorphodon and Campylognathoides form a family that basal to both Rhamphorhynchus and Quetzalcoatlus), and because Novialoidea was named first (in pages 105-137, while Lonchognatha was named in pages 139-190), Lonchognatha is an objective junior synonym of the former. However, other analyses find Lonchognatha to be valid (Andres et al., 2010) or synonymous with the Pterosauria (Andres, 2010 and Andres, in press).

Orionides

Orionides is a clade of tetanuran theropod dinosaurs from the Middle Jurassic to the Present. The clade includes most theropod dinosaurs, including birds.

Pelagosaurus

Pelagosaurus (meaning "lizard of the open sea") is an extinct genus of thalattosuchian crocodyliform that lived during the Toarcian stage of the Lower Jurassic, around 183 Ma to 175 Ma (million years ago), in shallow epicontinental seas that covered much of what is now Western Europe. The systematic taxonomy of Pelagosaurus has been fiercely disputed over the years, and was assigned to Thalattosuchia after its systematics within Teleosauridae were disputed. Pelagosaurus measured 3 m (10 ft) in length with a weight of 450 kg (1000 lbs), and was markedly similar to the modern-day gharial, which has similar adaptions and carnivorous feeding habits.

Pliensbachian

The Pliensbachian is an age of the geologic timescale and stage in the stratigraphic column. It is part of the Early or Lower Jurassic epoch or series and spans the time between 190.8 ± 1.5 Ma and 182.7 ± 1.5 Ma (million years ago). The Pliensbachian is preceded by the Sinemurian and followed by the Toarcian.The Pliensbachian ended with the extinction event called the Toarcian turnover. During the Pliensbachian, the middle part of the Lias was deposited in Europe. The Pliensbachian is roughly coeval with the Charmouthian regional stage of North America.

Protosuchidae

Protosuchidae was a family of crocodylmorph reptiles from the Late Triassic, Jurassic, and Cretaceous time periods. They were closely related to the Gobiosuchidae.

Rhamphorhynchidae

Rhamphorhynchidae is a group of early "rhamphorhynchoid" pterosaurs named after Rhamphorhynchus, that lived in the Late Jurassic. The family Rhamphorhynchidae was named in 1870 by Harry Govier Seeley.

Steneosaurus

Steneosaurus is an extinct genus of teleosaurid crocodyliform from the Early Jurassic to Middle Jurassic (Toarcian to Callovian). Fossil specimens have been found in England, France, Germany, Switzerland and Morocco. The largest species, S. heberti, reached up to 5 metres (16 ft) in length, though 2.5 to 3.5 metres (8.2 to 11.5 ft) was more common.

Tazoudasaurus

Tazoudasaurus is a genus of vulcanodontid sauropod dinosaurs hailing from the Early Jurassic Toundoute Group located in the High Atlas Mountains of Morocco in North Africa. The remains, consisting of a partial adult skeleton and associated partial juvenile skeleton found in continental detrital sediments of the Toarcian aged Toundoute Continental Series, were described by Ronan Allain et al. in early 2004. The generic name derives from one of the localities, Tazouda, while the specific descriptor is a latinization of the Arabic term for "slender" due to the animal's small size for a sauropod. Its fossil was found alongside that of Berberosaurus.

Tazoudasaurus, a small sauropod at 9 meters (30 feet) long, is characterized by rather primitive features such as the prosauropod-like mandible with spatulate and denticle-bearing teeth, lack of a U-shaped mandibular symphysis as other more derived sauropods. Teeth wear in V-shaped marks indicates tooth occlusion, suggesting that vulcanodontids processed food orally when feeding. The neck is flexible with elongate vertebrae that lack true pleurocoels while dorsal and caudal vertebrae series tend to be more rigid. T. naimi bears the most complete fossil skeleton for Early Jurassic sauropod remains found to date due to the scarcity of exposed strata of that age. This sauropod is most closely related to Vulcanodon, differing only in caudal vertebrae features while it also possesses characters that place it outside Eusauropoda.

Teleosauridae

The teleosaurids were marine crocodyliforms similar to the modern gharial that lived from the Early Jurassic to the Early Cretaceous. They had long snouts, indicative of piscivory (fish eating) and were the closest relatives to the Metriorhynchidae, the Mesozoic crocodilians that returned to the sea and evolved paddle-like forelimbs and a shark-like tail.

Toarcian turnover

The term Toarcian turnover, alternatively the Toarcian extinction, the Pliensbachian-Toarcian extinction, or the Early Jurassic extinction, refers to the wave of extinctions that marked the end of the Pliensbachian stage and the start of the Toarcian stage of the Early Jurassic period, c. 183 million years ago.

The Toarcian turnover was most strongly manifested in aquatic lifeforms, notably in mollusk groups like ammonites. Its reach was global in extent, as evidenced by research in European (peninsula of Peniche, Portugal) and Japanese waters, the Andean basin, the floor of the former Tethys Sea. Evidence points to anoxic bottom waters as the probable cause of these marine extinctions, linked in turn to the massive volcanism of the Karoo-Ferrar eruptions in the relevant era. The Toarcian turnover was the seventh-largest mass extinction in Earth's history.

Vulcanodontidae

The Early Jurassic sauropod dinosaurs Zizhongosaurus, Barapasaurus, Tazoudasaurus, and Vulcanodon may form a natural group of basal sauropods called the Vulcanodontidae. Basal vulcanodonts include some of the earliest known examples of sauropods. The family-level name Vulcanodontidae was erected by M.R. Cooper in 1984. In 1995 Hunt et al. published the opinion that the family is synonymous with the Barapasauridae. One of the key morphological features specific to the family is an unusually narrow sacrum.

Cenozoic era
(present–66.0 Mya)
Mesozoic era
(66.0–251.902 Mya)
Paleozoic era
(251.902–541.0 Mya)
Proterozoic eon
(541.0 Mya–2.5 Gya)
Archean eon (2.5–4 Gya)
Hadean eon (4–4.6 Gya)

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