Sinemurian

In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic epoch or series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago).[2] The Sinemurian is preceded by the Hettangian and is followed by the Pliensbachian.[3]

In Europe the Sinemurian age, together with the Hettangian age, saw the deposition of the lower Lias, in Great Britain known as the Blue Lias.

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

Cliff Face East Quantoxhead - geograph.org.uk - 1003272
Jurassic rock strata in the cliffs at East Quantoxhead, near the Sinemurian golden spike.

The Sinemurian stage was defined and introduced into scientific literature by French palaeontologist Alcide d'Orbigny in 1842. It takes its name from the French town of Semur-en-Auxois, near Dijon. The calcareous soil formed from the Jurassic limestone of the region is in part responsible for the character of the classic Sancerre wines.

The base of the Sinemurian stage is at the first appearance of the ammonite genera Vermiceras and Metophioceras in the stratigraphic record. A global reference profile (GSSP or golden spike) for the Sinemurian stage is located in a cliff north of the hamlet of East Quantoxhead, 6 kilometres east of Watchet, Somerset, England.[4]

Eteoderoceras armatum sinemurian
Eteoderoceras armatum, a Sinemurian ammonite

The top of the Sinemurian (the base of the Pliensbachian) is at the first appearances of the ammonite species Bifericeras donovani and ammonite genus Apoderoceras.

The Sinemurian contains six ammonite biozones in the Tethys domain:

Palaeontology

†Ichthyosaurs

Synapsids

Non-Mammaliaform Synapsids of the Sinemurian
Taxa Presence Location Description Images

Lufeng Formation

Mammaliaformes

Mammaliaformes of the Sinemurian
Taxa Presence Location Description Images
Yunnan, China The earliest known example of several features distinctive to mammals, including mammal-like mandible and middle-ear structures and a relatively large brain cavity.
From Norian to Sinemurian Greenland and Western Europe A Late Triassic-Early Jurassic symmetrodontan.

†Ornithischians

†Plesiosaurs

Theropoda

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. ^ See for the description of the GSSP Bloos & Page (2001)

Sources

  • Bloos, G. & Page, K.N.; 2001: Global Stratotype Section and Point for base of the Sinemurian Stage (Lower Jurassic), Episodes 25(1), pp. 22–28, PDF
  • 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)

See also

External links

Bienosaurus

Bienosaurus (meaning "Bien's lizard") is a genus of thyreophoran dinosaur from the Lower Jurassic (probably Sinemurian) Lower Lufeng Formation in Yunnan Province in China.

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.

Chigutisauridae

Chigutisauridae is an extinct family of large temnospondyl amphibians. The only genera recognized as belonging to Chigutisauridae at the current time are all from Gondwana (Australia, Argentina, India and South Africa) and include Koolasuchus and Siderops.

Cryolophosaurus

Cryolophosaurus ( or ; "CRY-oh-loaf-oh-SAWR-us") is a genus of large theropods known from only a single species Cryolophosaurus ellioti, known from the early Jurassic period of Antarctica. It was about 6.5 metres (21.3 ft) long and 465 kilograms (1,025 lb) in weight, making it one of the largest theropods of its time. Individuals of this species may have grown even larger, because the only known specimen probably represents a sub-adult. Cryolophosaurus is known from a skull, a femur and other material, the skull and femur of which have caused its classification to vary greatly. The femur possesses many primitive characteristics that have classified Cryolophosaurus as a dilophosaurid or a neotheropod outside of Dilophosauridae and Averostra, where as the skull has many advanced features, leading the genus to be considered a tetanuran, an abelisaurid, a ceratosaur and even an allosaurid. Since its original description, the consensus is that Cryolophosaurus is either a primitive member of the Tetanurae or a close relative of that group.

Cryolophosaurus possessed a distinctive "pompadour" crest that spanned the head from side to side. Based on evidence from related species and studies of bone texture, it is thought that this bizarre crest was used for intra-species recognition. The brain of Cryolophosaurus was also more primitive than those of other theropods.

Cryolophosaurus was first excavated from Antarctica's Early Jurassic, Sinemurian to Pliensbachian aged Hanson Formation, formerly the upper Falla Formation, by paleontologist Dr. William Hammer in 1991. It was the first carnivorous dinosaur to be discovered in Antarctica and the first non-avian dinosaur from the continent to be officially named. The sediments in which its fossils were found have been dated at ~194 to 188 million years ago, representing the Early Jurassic Period.

Dianzhongia

Dianzhongia is an extinct genus of tritylodont therapsids from the Sinemurian (Early Jurassic) of Yunnan, China. Only partial cranial remains from the Zhangjiawa locality of the Lufeng Formation can so far be attributed to this animal. It may be synonymous with the related genus Lufengia.

Goniopholididae

Goniopholididae is an extinct family of moderate-sized semi-aquatic crocodyliforms superficially similar to living crocodiles (but see below). They lived between the Early Jurassic and the Late Cretaceous.

Hettangian

The Hettangian is the earliest age and lowest stage of the Jurassic period of the geologic timescale. It spans the time between 201.3 ± 0.2 Ma and 199.3 ± 0.3 Ma (million years ago). The Hettangian follows the Rhaetian (part of the Triassic period) and is followed by the Sinemurian.In European stratigraphy the Hettangian is a part of the time span in which the Lias was deposited. An example is the British Blue Lias, which has an upper Rhaetian to Sinemurian age. Another example is the lower Lias from the Northern Limestone Alps where well-preserved but very rare ammonites, including Alsatites, have been found.

Kayentasuchus

Kayentasuchus (meaning "Kayenta Formation crocodile") is a genus of sphenosuchian, a type of basal crocodylomorph, the clade that comprises the crocodilians and their closest kin. It is known from a single skeleton found in rocks of the Sinemurian-Pliensbachian-age Lower Jurassic Kayenta Formation, northeastern Arizona.

Kunminia

Kunminia is a genus of cynodont synapsids from the Early Jurassic (Sinemurian) Lufeng Formation of China.

Ledumahadi

Ledumahadi (meaning "a giant thunderclap" in Sesotho language) is a genus of lessemsaurid sauropodomorph dinosaur from the Early Jurassic Elliot Formation in Free State Province, South Africa. The type and only species is L. mafube, known from a singular incomplete postcranial specimen. A quadruped, it was one of the first giant sauropodomorphs, reaching a weight of around 12 tonnes (26,000 lb), despite not having evolved columnar limbs like its later huge relatives.

Lufengia

Lufengia is an extinct genus of tritylodonts from the Sinemurian (Early Jurassic) of Yunnan, China. It may be a senior synonym to the related genus Dianzhongia, found nearby.

Lytoceras

Lytoceras is an ammonite genus that was extant during most of the Jurassic and Cretaceous periods, and is the type genus for the family Lytoceratidae. These cephalopods were fast-moving nektonic carnivores.

Mesoeucrocodylia

Mesoeucrocodylia is the clade that includes Eusuchia and crocodyliforms formerly placed in the paraphyletic group Mesosuchia. The group appeared during the Early Jurassic, and continues to the present day.

Microcleididae

Microcleididae is an extinct family of basal plesiosauroid plesiosaurs from the Early Jurassic (middle Sinemurian to late Toarcian stages) of France, Germany, Portugal and the United Kingdom. Currently, the oldest and the most known microcleidid is Eretmosaurus from the middle Sinemurian of the United Kingdom. Microcleididae was formally named and described by Roger B. J. Benson, Mark Evans and Patrick S. Druckenmiller in 2012.

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.

Pradhania

Pradhania is a genus of massospondylid sauropodomorph dinosaur from the Sinemurian-age (Early Jurassic) Upper Dharmaram Formation of India. It was first named by T. S. Kutty, Sankar Chatterjee, Peter M. Galton and Paul Upchurch in 2007 and the type species is Pradhania gracilis. It was a sauropodomorph of modest size, only about four meters (13 ft) long, and is known from fragmentary remains. It was originally regarded as a basal sauropodomorph but new cladistic analysis performed by Novas et al., 2011 suggests that Pradhania is a massospondylid. Pradhania presents two synapomorphies of Massospondylidae recovered in their phylogenetic analysis.

Protosuchidae

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

Pulanesaura

Pulanesaura is an extinct genus of basal sauropod known from the Early Jurassic (late Hettangian to Sinemurian) Upper Elliot Formation of the Free State, South Africa. It contains a single species, Pulanesaura eocollum, known from partial remains of at least two subadult to adult individuals.

Thalattosuchia

Thalattosuchia is the name given to a clade of marine crocodylomorphs from the Early Jurassic to the Early Cretaceous that had a cosmopolitan distribution. They are colloquially referred to as marine crocodiles or sea crocodiles, though they are not members of Crocodilia.

The term Thalattosuchia was coined by Fraas in 1901. Various authors considered Thalattosuchia an infraorder or a suborder within "Mesosuchia". However, the term "Mesosuchia" is a paraphyletic group, and as such is no longer used. For consistency, the Thalattosuchia are here placed at suborder rank, although the order that contains it is unnamed.

Since Buffetaut (1982) demonstrated the shared characteristics of the early forms of Metriorhynchidae and Teleosauridae, Thalattosuchia has consisted of these two families.Some of the early members of Teleosauridae have been discovered in non-marine deposits. The systematics of the genus Pelagosaurus are confused, with differencing topologies placing it as either a teleosaurid, or as the sister taxon to a Teleosauridae + Metriorhynchidae clade. Others considered Pelagosaurus to be a basal metriorhynchid.

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)
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