Early Jurassic

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Early Jurassic

:For general context see Jurassic
Jurassic

The Jurassic is a geologic period that extends from about annum to Ma, that is, from the end of the Triassic to the beginning of the Cretaceous....
. The Early Jurassic epoch

Epoch

Periodization* Epoch - A defining moment in the beginning of, or characteristic of, a distinctive historical period or era.* On the geologic time scale, a span of time smaller than a "period" and larger than an "age"....
(in chronostratigraphy

Chronostratigraphy

Chronostratigraphy is the branch of stratigraphy that studies the age of rock stratum in relation to time.The ultimate aim of chronostratigraphy is to arrange the sequence of deposition and the time of deposition of all rocks within a geological region, and eventually, the entire geologic record of the Earth....
corresponding to the Lower Jurassic series

Series (stratigraphy)

Series are subdivisions of stratum made based on the age of the rock. A series is therefore a chronostratigraphy unit, unrelated to lithostratigraphy, which divides rock layers on their lithology....
, originally (and still in Europe) the "Lias") is the earliest of three epochs of the Jurassic

Jurassic

The Jurassic is a geologic period that extends from about annum to Ma, that is, from the end of the Triassic to the beginning of the Cretaceous....
period.

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Epoch

Chronostratigraphy

Series (stratigraphy)

Jurassic

The Jurassic is a geologic period that extends from about annum to Ma, that is, from the end of the Triassic to the beginning of the Cretaceous....
period. The Early Jurassic starts immediately after the Triassic-Jurassic extinction event

Triassic-Jurassic extinction event

The Triassic?Jurassic extinction event marks the boundary between the Triassic and Jurassic periods, , and is one of the major extinction events of the Phanerozoic eon, profoundly affecting life on land and in the oceans....
(199.6 Ma (million years ago)) and ends at the start of the Middle Jurassic

Middle Jurassic

The Middle Jurassic, called the Dogger in the European system of classification, is the second epoch of the Jurassic Period . It lasted from 176-161 million years ago....
(175.6 Ma).

Origin of the name Lias

There are two possible origins for the name Lias: the first reason is it was taken by a geologist

Geologist

For other uses, see Geologist .A geologist is a contributor to the science of geology, studying the physical structure and processes of the Earth and planets of the solar system ....
from an English

England

Dialect

A dialect is a variety of a language that is characteristic of a particular group of the language's speakers. The term is applied most often to regional speech patterns, but a dialect may also be defined by other factors, such as social class....
pronunciation of the word "layers"; secondly, sloops from North

North

North is one of the four cardinal directions, specifically the direction that, in Western culture, is treated as the fundamental direction:...
Cornwall

Cornwall

Cornwall , constitutional Duchy and palatine, is a metropolitan and non-metropolitan counties of England of England, United Kingdom, located at the tip of the south-western peninsula of Great Britain....
ports such as Bude

Bude

Bude is a small seaside resort town in North Cornwall, England, United Kingdom, at the mouth of the River Neet. Bude is twinned with Ergué-Gabéric, France....
would sail to the Vale of Glamorgan

Vale of Glamorgan

The Vale of Glamorgan is an exceptionally rich agricultural area in the southern part of Glamorgan, Wales. It has a rugged coastline, but its rolling countryside is quite atypical of Wales as a whole....
heritage coast to load up on lias limestone (lias limestone from South Wales was used throughout North Devon/North Cornwall as it contains calcium carbonate to fertilise the poor quality Devonian soils of the West Country); the Cornish would pronounce the layers of limestone as 'laiyers' or 'lias'.

Geology

There are extensive Liassic outcrops around the coast of the UK

United Kingdom

The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom , the UK or Britain,is a sovereign state located off the northwestern coast of continental Europe....
, in particular in the Dorset

Dorset

Dorset , is a Counties of England in South West England on the English Channel coast. The county town is Dorchester, Dorset, situated in the south of the county at ....
Jurassic coast

Jurassic Coast

The Jurassic Coast is a World Heritage Site on the English Channel coast of southern England. The site stretches from Orcombe Point near Exmouth, Devon in East Devon to Old Harry Rocks near Swanage in East Dorset, a distance of ....
, often associated with the pioneering work of Mary Anning

Mary Anning

Mary Anning was an early British fossil collector and paleontology....
of Lyme Regis

Lyme Regis

Lyme Regis is a coastal town in West Dorset, England, situated 25 miles west of Dorchester, Dorset and east of Exeter. The town lies in Lyme Bay, on the English Channel coast at the Dorset-Devon border....
. The facies

Facies

In geology, facies are a body of rock with specified characteristics. [Reading ] Ideally, a facies is a distinctive rock unit that forms under certain conditions of sedimentation, reflecting a particular process or environment....
of the Lower Jurassic in this area are predominantly of clays, thin limestones and siltstones, deposited under fully marine conditions.

Perhaps the best example of a Liassic coastline in the world are the superb cliffs of the Vale of Glamorgan

Vale of Glamorgan

Wales

native_name = Cymru|conventional_long_name = Wales|common_name = Wales|image_flag = Flag of Wales 2.svg|national_motto = ...
. Stretching for around 14 miles just outside Cardiff

Cardiff

Cardiff is the Capital , largest city and most populous Unitary authority#Wales in Wales. The city is Wales' chief commercial centre, the base for many national cultural and sport institutions, the Welsh national media, and the seat of Welsh Assembly Government ....
, the remarkable strata

Stratum

In geology and related fields, a stratum is a layer of rock or soil with internally consistent characteristics that distinguishes it from contiguous layers....
of the cliffs, situated on the Bristol Channel

Bristol Channel

The Bristol Channel is a major inlet in the island of Great Britain, separating South Wales from Devon and Somerset in South West England, and extending from the lower Severn Estuary of the River Severn to that part of the North Atlantic Ocean known as the Celtic Sea ....
are a mixture of Carboniferous

Carboniferous

The Carboniferous is a geologic period that extends from the end of the Devonian period, about 359.2 ? 2.5 annum , to the beginning of the Permian period, about 299.0 ? 0.8 Ma ...
sandstone

Sandstone

Sandstone is a sedimentary rock composed mainly of sand-size mineral or rock Particle size . Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust ....
/limestone

Limestone

File:Limestone Formation In Waitomo.jpgLimestone is a sedimentary rock composed largely of the mineral calcite . The deposition of limestone strata is often a by-product and indicator of biological activity in the geology record....
, shale

Shale

Shale is a fine-grained sedimentary rock whose original constituents were clay minerals or muds. It is characterized by thin laminae breaking with an irregular curving fracture, often splintery and usually parallel to the often-indistinguishable bedding plane....
and liassic limestone

Limestone

Variscan orogeny

The Variscan orogeny is a geologic mountain-building event caused by Late Paleozoic continental collision between Laurasia and Gondwana to form the supercontinent of Pangea....
.

Stratigraphy

There has been some debate over the actual base of the Hettangian

Hettangian

The Hettangian is the first faunal stage of the Early Jurassic epoch . It spans the time between 199.6 ? 0.6 annum and 196.5 ? 1 Ma . The stage follows the Rhaetian Stage of the Triassic Period....
stage, and so of the Jurassic system itself. Biostratigraphically

Biostratigraphy

Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock Stratum by using the fossil assemblages contained within them....
, the first appearance of psiloceratid ammonites has been used; but this depends on relatively complete ammonite faunas being present, a problem that makes correlation between sections in different parts of the world difficult. If this biostratigraphical indicator is used, then technically the Lias Group

Lias Group

The Lias Group or Lias is a lithostratigraphy unit found in a large area of western Europe, including the British Isles, the North Sea, the low countries and the north of Germany....
— a lithostratigraphical

Lithostratigraphy

Lithostratigraphy is a sub-discipline of stratigraphy, the geology science associated with the study of stratum or rock layers. Major focuses include geochronology, comparative geology, and petrology....
division — spans the Jurassic / Triassic

Triassic

The Triassic is a geologic period that extends from about 251 to 199 annum . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic....
boundary.

Life

Ammonites

During this period, ammonoids, which had almost died out at the end-of-Triassic extinction, radiated out into a huge diversity of new forms with complex suture patterns (the ammonites proper). Ammonites evolved so rapidly, and their shells are so often preserved, that they serve as important zone fossils. There were several distinct waves of ammonite evolution in Europe alone.

Marine reptiles

The Early Jurassic was an important time in the evolution of the marine reptiles. The Hettangian saw the already existing Rhaetian

Rhaetian

PaleogeographyAt this stage, Pangaea began to break-up, though the Atlantic Ocean was not yet formed....
ichthyosaur

Ichthyosaur

Ichthyosaurs were giant marine reptiles that resembled fish and dolphins. Ichthyosaurs thrived during much of the Mesozoic era; based on fossil evidence, they first appeared approximately 245 million years ago and disappeared about 90 million years ago, about 25 million years before the dinosaurs became extinct....
s and plesiosaur

Plesiosaur

Plesiosaurs were carnivore aquatic reptiles. After their discovery, they were somewhat fancifully said to have resembled , although they had no shell....
s continuing to flourish, while at the same time a number of new types of these marine reptile

Marine reptile

Marine reptiles are reptiles which have become secondarily adaptation for an aquatic animal or semi-aquatic life in a marine Natural environment....
s appeared, such as 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....
and Temnodontosaurus
Temnodontosaurus

Temnodontosaurus was an ichthyosaur from the Early Jurassic, some 198 and 185 million years ago , in Europe . It was a large genus, exceeded 12 meters in length....
among the ichthyosaurs, and Eurycleidus
Eurycleidus

is an extinct genus of plesiosaur.See also* List of plesiosaursReferences...
, Macroplata
Macroplata

Macroplata is an extinct genus of Early Jurassic pliosaur, which grew up to 4.5 meters in length. Like other pliosaurs, Macroplata probably lived on a diet of fish, using its sharp needle-like teeth to catch prey....
, and Rhomaleosaurus
Rhomaleosaurus

Rhomaleosaurus is an extinct genus of sauropterygian reptile belonging to the pliosaur superfamily. It was about long and lived in the Early Jurassic Period....
among the plesiosaurs (all Rhomaleosauridae, although as currently defined this group is probably paraphyletic). All these plesiosaurs had medium-sized necks and large heads. In the Toarcian

Toarcian

The Toarcian Stage was the last faunal stage of the Early Jurassic period. It is usually used to cover the period from 183 annum to 175 Ma .The Toarcian stage began with the Toarcian turnover, the extinction event that set it apart from the previous Pliensbachian stage....
, at the end of the Early Jurassic, the thalattosuchians

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....
(marine "crocodiles

Crocodylomorpha

The Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now....
") appeared, as did new genera

Genus

A genus is a low-level taxonomic rank used in the classification of living and fossil organisms. The taxonomic ranks are domain , kingdom , phylum, class , order , family , genus, and species....
of ichthyosaurs (Stenopterygius
Stenopterygius

Stenopterygius is an extinct genus of ichthyosaur from the Early to Middle Jurassic from Europe . Maximum length was 4 m....
, Eurhinosaurus
Eurhinosaurus

Eurhinosaurus is an extinct genus of ichthyosaur from the Early Jurassic of Europe . It was a large genus, exceeding 6 m in length....
, and the persistently primitive Suevoleviathan) and plesiosaurs (the elasmosaurs

Elasmosauridae

Elasmosauridae was the family of plesiosaurs. They had the longest necks of the plesiosaurs and survived from the Early Jurassic to the end of the Cretaceous....
(long-necked) Microcleidus
Microcleidus

Microcleidus is an extinct genus of sauropterygian reptile belonging to the plesiosaur suborder. It was about the size of a whale.Species include: Microcleidus homalospondylus and Microcleidus macropterus ....
and Occitanosaurus
Occitanosaurus

Occitanosaurus is an extinction genus of plesiosaur from the Early Jurassic of what is now France. The type species is Occitanosaurus tournemirensis , first named by Sciau et al. in 1990....
, and the pliosaur Hauffiosaurus
Hauffiosaurus

is an extinct genus of plesiosaur.See also* List of plesiosaursReferences...
).

Terrestrial animals

On land, a number of new types of dinosaurs - the heterodontosaurids

Heterodontosauridae

Heterodontosauridae is a family of early ornithischian dinosaurs that have often been considered Basal ornithopods, although recent studies suggest they may have been more closely related to marginocephalians....
, scelidosaurs

Scelidosaurus

Scelidosaurus is a genus of quadrupedal, lightly plated, Herbivore dinosaur about 4 metres long . It lived during the Early Jurassic Period , during the Hettangian to Sinemurian faunal stage around 208 to 194 mya ....
, stegosaurs, and tetanurae

Tetanurae

Tetanurae, or "stiff tails", is a clade that includes most theropod dinosaurs, as well as birds. Tetanurans first appear during the early Jurassic period....
, appeared, and joined those groups like the podokesaurs

Podokesaurus

Podokesaurus was a small carnivore dinosaur of the Early Jurassic Period , and as such is one of the earliest known dinosaurs to inhabit the eastern United States ....
, prosauropods

Prosauropoda

Prosauropoda or prosauropods were a group of early herbivorous dinosaurs that lived during the Triassic and early Jurassic periods. They were frequently the predominant herbivore in their environment, and quickly reached large size ....
and the sauropods that had continued over from the Triassic. Accompanying them as small carnivores were the sphenosuchid

Sphenosuchia

Sphenosuchia is the name of a suborder of basal crocodylomorphs that first appeared in the Triassic and occurred into the Middle Jurassic. Most were small, gracile animals with an erect limb posture....
and protosuchid

Protosuchus

Protosuchus is an extinct genus of carnivorous crocodylomorph from the Early Jurassic. The name Protosuchus means "first crocodile", and is among the earliest animals that resemble crocodilians....
crocodilians. In the air, new types of pterosaur

Pterosaur

Pterosaurs were flying reptiles of the clade or Order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight....
s replaced those that had died out at the end of the Triassic. While in the undergrowth were various types of early mammals, as well as tritylodont

Tritylodontidae

Tritylodontids were small to medium-sized, highly specialized and extremely mammal-like cynodonts. They were the last family of the non-mammalian synapsids....
mammal-like reptiles, lizard-like sphenodonts, and early Lissamphibia

Lissamphibia

The Subclass Lissamphibia includes all recent amphibians.Extant amphibians fall into one of three orders - the Anura , the Caudata or Urodela , and the Gymnophiona or Apoda ....
ns.