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]

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]

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.

Stratigraphic definitions
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, 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

Amphibians
Amphibians of the Pliensbachian
Taxa Presence Location Description Images
Kayenta Formation, Arizona Currently the oldest known anuran, which lived well before the first known modern frog, Callobatrachus of the Early Cretaceous .
Prosalirus

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.

Sauropsids

†Ichthyosaurs
Ichthyosauria of the Sinemurian
Taxa Presence Location Description Images
From Hettangian to Sinemurian Belgium, England, Germany Among the best known ichthyosaur genera, was smaller than most of its relatives, measuring 2 m (6 ft 7 in) in length.
Ichthyosaurus
Europe
Hettangian to Toarcian All over Europe An ichthyosaur that exceeded 12 metres (39 ft) in length

†Plesiosaurs
Plesiosauria of the Sinemurian
Taxa Presence Location Description Images
Blue Lias Formation, England A rhomaleosaurid pliosaur.
Archaeonectrus
Attenborosaurus
Plesiosaurus
Blue Lias Formation, England A basal pliosaurid around 5 meters long.
Granby, Leicestershire, England May have been a rhomaleosaurid, pliosaurid, microcleidid or elasmosaurid
Sinemurian and Toarcian Lyme Regis, Dorset, England 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

Archosaurs
Crocodylomorpha
Crocodylomorphs of the Sinemurian
Taxa Presence Location Description Images
Dark Red Beds, Lufeng Formation, Yunnan, China Dibothrosuchus was a sphenosuchian, a basal crocodylomorph.
Dibothrosuchus
Kayenta Formation, Arizona Despite the similar cranial morphology with crocodilians, the genus is currently regarded as a basal crocodyliform although more derived than protosuchians.
South Africa A small, gracile non-crocodyliform sphenosuchian crocodylomorph.
Litargosuchus leptorhynchus
Red Beds Formation, Qacha's Nek Province, Lesotho A genus of small protosuchian crocodyliforms.
Dark Red Beds, Lufeng Formation, Yunnan, China A sphenosuchian crocodylomorph. Because some of its teeth were leaf-shaped it does not appear to have been a strict carnivore like most other crocodylomorphs.
†Ornithischians
Ornithischians of the Sinemurian
Taxa Presence Location Description Images
From Hettangian to Sinemurian Upper Elliot Formation, Lesotho and Cape Province, South Africa Considered the most basal member of the family Heterodontosauridae
Abrictosaurus
Scelidosaurus
Scutellosaurus
Lower Lufeng Formation, Yunnan, China A dubious genus of thyreophoran dinosaur. Possibly identical to Tatisaurus.
From Hettangian to Sinemurian Lesotho As the only fossil known of it is a partial jawbone with three teeth, Fabrosaurus is a nomen dubium and may in fact be the same as Lesothosaurus.
Clarence Formation, Cape Province, South Africa With few remains, it is considered a nomen dubium. It is classified as an ornithischian based on the jaw.
From Hettangian to Sinemurian Upper Elliot Formation, Orange Free State, South Africa A heterodontosaurid ornithischian
Date disputed Unknown location in Portugal Only known from a partial snout with teeth. Lusitanosaurus is a genus of large basal thyreophoran dinosaur, probably closely related to Scelidosaurus.
From Hettangian to Sinemurian Upper Elliot Formation, Cape Province, South Africa A small herbivore dinosaur despite long canines it sported in its jaws; due to this unique characteristic it is very clearly allied to Heterodontosaurus
  • Merosaurus
 England Disputed, considered by some to be a tetanuran theropod
From Hettangian to Sinemurian Charmouth, West Dorset, England; Kayenta Formation, Arizona, USA A genus of quadrupedal, lightly plated, herbivorous dinosaur about 4 meters (13 feet) long. A basal member of Thyreophora.
Sinemurian Kayenta Formation, Arizona, USA One of the earliest representatives of the armored dinosaurs and the basalmost form discovered to date. It was a small, lightly-built, ground-dwelling, herbivore, that could grow up to an estimated 1.2 m (3.9 ft) long.
From Hettangian to Sinemurian Stormberg Series Formations, South Africa, Lesotho A primitive ornithischian, about 2 meters (6 feet 7 inches) long. The proportions of the posterior limbs show differences with those of Lesothosaurus, and reveal a lower ability to run
Lufeng Formation, Yunnan, China Tatisaurus is a genus of basal ornithischian dinosaur from China. Little is known as the remains are fragmentary but it's likely a thyreophoran related to Scutellosaurus and Scelidosaurus.
Theropoda
Theropods of the Sinemurian
Taxa Presence Location Description Images
Sinemurian Kayenta Formation, Arizona, USA A medium-small sized theropod, C. kayentakatae had two small, parallel crests which may demonstrate an evolutionary step toward later and larger neotheropods, such as the more advanced and larger Dilophosaurus and Sinosaurus.
Coelophysis kayentakatae
Sinosaurus
Sinemurian to Pliensbachian Arizona, USA Measured around six meters (20 ft) long and may have weighed half a ton. The most distinctive characteristic of Dilophosaurus is the pair of rounded crests on its skull, possibly used for display.
Sinemurian Leicestershire, England Measured around 3.5 meters (11 feet) long. The most distinctive characteristic of Sarcosaurus is its pelvis which is remarkably similar to Dilophosaurus
Early Sinemurian Saltrio, Northern Italy Measured 7,5 meters and weighed one ton. It was a basal Ceratosaur.
Sinemurian Zhangjiawa Member, Lufeng Formation, Yunnan, China Sinosaurus was a tetanuran theropod. It measured approximately 5.6 meters in length.
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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
  • Komlosaurus carbonis
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