The Hettangian is the earliest age or lowest stage of the Jurassic

Jurassic

The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

 period of the geologic timescale. It spans the time between 199.6 ± 0.6 Ma and 196.5 ± 1 Ma (million years ago). The Hettangian follows the Rhaetian

Rhaetian

The Rhaetian is in geochronology the latest age of the Triassic period or in chronostratigraphy the uppermost stage of the Triassic system. It lasted from 203.6 ± 1.5 to 199.6 ± 0.6 million years ago...

 (part of the Triassic

Triassic

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

 period) and is followed by the Sinemurian

Sinemurian

In the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...

.

In Europe stratigraphy the Hettangian is a part of the time span in which the Lias

Lias

Lias may refer to:*In geology:**The Lias Group, a group in the stratigraphy of Great Britain, formed during the Late Triassic to Early Jurassic epochs. It includes the Blue Lias and White Lias...

 was deposited. An example is the British Blue Lias

Blue Lias

The Blue Lias is a geologic formation in southern, eastern and western England and parts of South Wales, part of the Lias Group. The Blue Lias consists of a sequence of limestone and shale layers, laid down in latest Triassic and early Jurassic times, between 195 and 200 million years ago...

, which has an upper Rhaetian to Sinemurian age.

Stratigraphic definitions

The Hettangian was introduced in the literature by Swiss palaeontologist, Eugène Renevier

Eugène Renevier

Eugène Renevier Swiss geologist, was born at Lausanne, Switzerland, as a descendant of a noble family.In 1857 he became professor of geology and paleontology in the University of Lausanne...

, in 1864. The stage takes its name from Hettange-Grande

Hettange-Grande

Hettange-Grande is a commune in the Moselle department in Lorraine in north-eastern France.-Geography:Hettange-Grande is located close to the borders between France, Germany, and Luxembourg.-History:...

, a town in northern France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, just south of the border with Luxembourg

Luxembourg

Luxembourg , officially the Grand Duchy of Luxembourg , is a landlocked country in western Europe, bordered by Belgium, France, and Germany. It has two principal regions: the Oesling in the North as part of the Ardennes massif, and the Gutland in the south...

 on the main road from Luxembourg City to Metz

Metz

Metz is a city in the northeast of France located at the confluence of the Moselle and the Seille rivers.Metz is the capital of the Lorraine region and prefecture of the Moselle department. Located near the tripoint along the junction of France, Germany, and Luxembourg, Metz forms a central place...

.

The base of the Hettangian stage (which is also the base of the Lower Jurassic series

Series (stratigraphy)

Series are subdivisions of rock layers made based on the age of the rock and corresponding to the dating system unit called an epoch, both being formally defined international conventions of the geological timescale. A series is therefore a sequence of rock depositions defining a...

 and the entire Jurassic system) is defined as the place in the stratigraphic column where fossils of the ammonite

Ammonite

Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct subclass within the Molluscan class Cephalopoda which are more closely related to living coleoids Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct...

 genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Psiloceras

Psiloceras

Psiloceras is an extinct genus of cephalopod belonging to the ammonite subclass. Psiloceras fossils are commonly found at Lyme Regis, Dorset Coast, England. Here smooth-shelled Psiloceras planorbis are to be found as usually flattened fossils in the Blue Lias....

first appear. A global reference profile (a GSSP) for the base had in 2009 not yet been appointed, but a section at Kuhjoch in western Austria

Austria

Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...

 has been proposed. The top of the Hettangian stage (the base of the Sinemurian) is at the first appearances of ammonite genera

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Vermiceras and Metophioceras.

Biostratigraphy

The Hettangian contains three ammonite biozone

Biozone

Biostratigraphic units or Biozones are intervals of geological strata that are defined on the basis of their characteristic fossil taxa....

s in the Tethys domain

Tethys Ocean

The Tethys Ocean was an ocean that existed between the continents of Gondwana and Laurasia during the Mesozoic era before the opening of the Indian Ocean.-Modern theory:...

:

• zone of Schlotheimia angulata
• zone of Alsatites liasicus
  Alsatites
  Alsatites is an extinct genus of cephalopod belonging to the Ammonite subclass....
  
  
• zone of Psiloceras planorbis
  Psiloceras
  Psiloceras is an extinct genus of cephalopod belonging to the ammonite subclass. Psiloceras fossils are commonly found at Lyme Regis, Dorset Coast, England. Here smooth-shelled Psiloceras planorbis are to be found as usually flattened fossils in the Blue Lias....
  
  

†Ichthyosaurs

Ichthyosauria of the Hettangian
Taxa	Presence	Location	Description	Images
Ichthyosaurus Ichthyosaurus Ichthyosaurus is an extinct genus of ichthyosaur from the Early Jurassic of Europe . It is among the best known ichthyosaur genera, with the Order Ichthyosauria being named after it...	From Hettangian to Sinemurian Sinemurian In the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...	Belgium, England, Germany	Among the best known ichthyosaur genera, was smaller than most of its relatives, measuring 2 m (6 ft 6 inches) in length.

Mammaliaformes

Mammaliaformes Mammaliaformes Mammaliaformes is a clade that contains the mammals and their closest extinct relatives. Phylogenetically, it is defined as a clade including the most recent common ancestor of Sinoconodon, morganuconodonts, docodonts, Monotremata, Marsupialia, Placentalia, extinct members of this clade, and all...  of the Hettangian
Taxa	Presence	Location	Description	Images
Haramiya Haramiya Haramiya is a mammaliform that is a lineage either unrelated or a paraphyletic parent to multituberculates from the Mesozoic era.Only Haramiyas teeth and skull have been found; judging from these it has been constructed as a 12 cm creature with a resemblance to modern voles...

†Ornithischians

Ornithischians of the Hettangian
Taxa	Presence	Location	Description	Images
Abrictosaurus Abrictosaurus Abrictosaurus is a genus of heterodontosaurid dinosaur from the Early Jurassic Period of what is now southern Africa. It was a small bipedal herbivore or omnivore, approximately 1.2 meters long, and weighing less than 45 kilograms .This dinosaur is known from the fossil remains of only...	From Hettangian to Sinemurian Sinemurian In the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...	Upper Elliot Formation Upper Elliot Formation The Upper Elliot Formation is a geological formation dating to roughly between 200 to 190 million years ago and covering the Hettangian to Sinemurian stages. The Upper Elliot Formation is found in South Africa and Lesotho and is a member of the Stormberg Group. It consists mainly of limestone,... , Lesotho and Cape Province, South Africa	Considered the most basal member of the family Heterodontosauridae
Fabrosaurus Fabrosaurus Fabrosaurus ) was a genus of herbivorous dinosaur which lived during the Early Jurassic . 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.Fabrosaurus was around 1 meter long...	From Hettangian to Sinemurian Sinemurian In the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...	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 Lesothosaurus Lesothosaurus is an herbivorous ornithischian dinosaur. It was named by paleontologist Peter Galton in 1978, the name meaning "lizard from Lesotho". The genus is monotypic, having only one valid species, Lesothosaurus diagnosticus, within the genus.... .
Heterodontosaurus Heterodontosaurus Heterodontosaurus is a genus of small herbivorous dinosaur with prominent canine teeth which lived in the Early Jurassic of South Africa. It was similar to a hypsilophodont in shape, and ate plants, despite its canines.Heterodontosaurus is currently known from specimens of the SAFM from South...		Upper Elliot Formation Upper Elliot Formation The Upper Elliot Formation is a geological formation dating to roughly between 200 to 190 million years ago and covering the Hettangian to Sinemurian stages. The Upper Elliot Formation is found in South Africa and Lesotho and is a member of the Stormberg Group. It consists mainly of limestone,... , Cape Province, South Africa	A small, fleet-footed ornithischian that reached a maximum size of about 3 feet. The hand of Heterodontosaurus had five fingers, two of which seem to be opposable, allowing Heterodontosaurus to grasp and manipulate food. Another interesting feature is the specialization of teeth which gave rise to the animal's name. At the front of the jaw beside the beak were small teeth likely used for chopping off leaves and stems.
Lanasaurus	From Hettangian to Sinemurian Sinemurian In the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...	Upper Elliot Formation Upper Elliot Formation The Upper Elliot Formation is a geological formation dating to roughly between 200 to 190 million years ago and covering the Hettangian to Sinemurian stages. The Upper Elliot Formation is found in South Africa and Lesotho and is a member of the Stormberg Group. It consists mainly of limestone,... , Orange Free State, South Africa	A heterodontosaurid ornithischian
Lycorhinus Lycorhinus Lycorhinus is a genus of heterodontosaurid ornithischian dinosaur hailing from the Early Jurassic strata of the Elliot Formation located in the Cape Province, South Africa....	From Hettangian to Sinemurian Sinemurian In the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...	Upper Elliot Formation Upper Elliot Formation The Upper Elliot Formation is a geological formation dating to roughly between 200 to 190 million years ago and covering the Hettangian to Sinemurian stages. The Upper Elliot Formation is found in South Africa and Lesotho and is a member of the Stormberg Group. It consists mainly of limestone,... , 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
Scelidosaurus Scelidosaurus Scelidosaurus is a genus of quadrupedal, lightly plated, herbivorous dinosaur about long. It lived during the Early Jurassic Period, during the Hettangian to Sinemurian stages around 199.6 to 194 million years ago. Its fossils have been found in both England and in Arizona, in the United...	From Hettangian to Sinemurian Sinemurian In the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...	Charmouth Charmouth Charmouth is a village at the mouth of the River Char in West Dorset, England, with a population of 1,687 according to the 2001 census.-The village:... , West Dorset, England; Kayenta Formation Kayenta Formation The Kayenta Formation is a geologic layer in the Glen Canyon Group that is spread across the Colorado Plateau province of the United States, including northern Arizona, northwest Colorado, Nevada, and Utah. This rock formation is particularly prominent in southeastern Utah, where it is seen in the... , Arizona, USA	A genus of quadrupedal, lightly plated, herbivorous dinosaur about 4 meters long (13 ft)
Scutellosaurus Scutellosaurus Scutellosaurus is a genus of herbivorous dinosaur that lived in North America around 200 to 196 million years ago, in the Early Jurassic times....		Arizona, USA	A bipedal armored herbivore, was around 1.3 m (4 ft 4 inches) long, 0.5 m (18 in) tall at the hips, and weighed 10 kg (22 lb).
Stormbergia Stormbergia Stormbergia is a genus of early ornithischian dinosaur known from the upper Elliot Formation of South Africa and Lesotho, named by Richard Butler in 2005...	From Hettangian to Sinemurian Sinemurian In the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...	Stormberg Series Formations, South Africa, Lesotho	A primitive ornithischian, about 2 meters long. The proportions of the posterior limbs show differences with those of Lesothosaurus Lesothosaurus Lesothosaurus is an herbivorous ornithischian dinosaur. It was named by paleontologist Peter Galton in 1978, the name meaning "lizard from Lesotho". The genus is monotypic, having only one valid species, Lesothosaurus diagnosticus, within the genus.... , and reveal a lower ability to run

†Plesiosaurs

Plesiosauria Plesiosauria Plesiosauria is an order of Mesozoic marine reptiles. Plesiosaurs first appeared in the Early Jurassic Period and became especially common during the Jurassic Period, thriving until the K-T extinction at the end of the Cretaceous Period.The name "plesiosaur" is used to refer to the order...  of the Hettangian
Taxa	Presence	Location	Description	Images
Macroplata Macroplata Macroplata , meaning, , is an extinct genus of Early Jurassic basal plesiosaur which grew up to in length. Like other plesiosaurs, Macroplata probably lived on a diet of fish, using its sharp needle-like teeth to catch prey. Its shoulder bones were fairly large, indicating a powerful forward...	Hettangian to Toarcian Toarcian The Toarcian is, in the ICS' geologic timescale, an age or stage in the Early or Lower Jurassic. It spans the time between 183.0 Ma and 175.6 Ma...	Harbury Harbury Harbury is a village and civil parish in the Stratford-on-Avon district of Warwickshire, England. In the 2001 census it had a population of 2,485.... , Warwickshire, UK
Rhomaleosaurus Rhomaleosaurus Rhomaleosaurus is an extinct genus of Early Jurassic rhomaleosaurid pliosauroid known from Northamptonshire and from Yorkshire of the United Kingdom. It was first named by Harry Seeley in 1874 and the type species is Rhomaleosaurus cramptoni...	Hettangian and Toarcian Toarcian The Toarcian is, in the ICS' geologic timescale, an age or stage in the Early or Lower Jurassic. It spans the time between 183.0 Ma and 175.6 Ma...	Barrow-upon-Soar, Leicestershire, England	A genus of sauropterygian carnivorous reptile belonging to the pliosaur superfamily, it was about 7m long.

Literature

; 2004: A Geologic Time Scale 2004, Cambridge University Press

Cambridge University Press

Cambridge University Press is the publishing business of the University of Cambridge. Granted letters patent by Henry VIII in 1534, it is the world's oldest publishing house, and the second largest university press in the world...

.: Notices géologiques et paléontologiques sur les Alpes Vaudoises, et les régions environnantes. I. Infralias et Zone à Avicula contorta (Étage Rhaetien) des Alpes Vaudoises Bulletin de la Société Vaudoise des Sciences Naturelles 8, p. 39-97.

External links

• GeoWhen Database - Hettangian
• 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