England is a country, part of the United Kingdom. It shares land borders with Wales to Scotland to the north-northwest; the Irish Sea lies west of England and the Celtic Sea lies to the southwest. England is separated from continental Europe by the North Sea to the east and the English Channel to the south; the country covers five-eighths of the island of Great Britain, which lies in the North Atlantic, includes over 100 smaller islands, such as the Isles of Scilly and the Isle of Wight. The area now called England was first inhabited by modern humans during the Upper Palaeolithic period, but takes its name from the Angles, a Germanic tribe deriving its name from the Anglia peninsula, who settled during the 5th and 6th centuries. England became a unified state in the 10th century, since the Age of Discovery, which began during the 15th century, has had a significant cultural and legal impact on the wider world; the English language, the Anglican Church, English law – the basis for the common law legal systems of many other countries around the world – developed in England, the country's parliamentary system of government has been adopted by other nations.
The Industrial Revolution began in 18th-century England, transforming its society into the world's first industrialised nation. England's terrain is chiefly low hills and plains in central and southern England. However, there is upland and mountainous terrain in the west; the capital is London, which has the largest metropolitan area in both the United Kingdom and the European Union. England's population of over 55 million comprises 84% of the population of the United Kingdom concentrated around London, the South East, conurbations in the Midlands, the North West, the North East, Yorkshire, which each developed as major industrial regions during the 19th century; the Kingdom of England – which after 1535 included Wales – ceased being a separate sovereign state on 1 May 1707, when the Acts of Union put into effect the terms agreed in the Treaty of Union the previous year, resulting in a political union with the Kingdom of Scotland to create the Kingdom of Great Britain. In 1801, Great Britain was united with the Kingdom of Ireland to become the United Kingdom of Great Britain and Ireland.
In 1922 the Irish Free State seceded from the United Kingdom, leading to the latter being renamed the United Kingdom of Great Britain and Northern Ireland. The name "England" is derived from the Old English name Englaland, which means "land of the Angles"; the Angles were one of the Germanic tribes that settled in Great Britain during the Early Middle Ages. The Angles came from the Anglia peninsula in the Bay of Kiel area of the Baltic Sea; the earliest recorded use of the term, as "Engla londe", is in the late-ninth-century translation into Old English of Bede's Ecclesiastical History of the English People. The term was used in a different sense to the modern one, meaning "the land inhabited by the English", it included English people in what is now south-east Scotland but was part of the English kingdom of Northumbria; the Anglo-Saxon Chronicle recorded that the Domesday Book of 1086 covered the whole of England, meaning the English kingdom, but a few years the Chronicle stated that King Malcolm III went "out of Scotlande into Lothian in Englaland", thus using it in the more ancient sense.
According to the Oxford English Dictionary, its modern spelling was first used in 1538. The earliest attested reference to the Angles occurs in the 1st-century work by Tacitus, Germania, in which the Latin word Anglii is used; the etymology of the tribal name itself is disputed by scholars. How and why a term derived from the name of a tribe, less significant than others, such as the Saxons, came to be used for the entire country and its people is not known, but it seems this is related to the custom of calling the Germanic people in Britain Angli Saxones or English Saxons to distinguish them from continental Saxons of Old Saxony between the Weser and Eider rivers in Northern Germany. In Scottish Gaelic, another language which developed on the island of Great Britain, the Saxon tribe gave their name to the word for England. An alternative name for England is Albion; the name Albion referred to the entire island of Great Britain. The nominally earliest record of the name appears in the Aristotelian Corpus the 4th-century BC De Mundo: "Beyond the Pillars of Hercules is the ocean that flows round the earth.
In it are two large islands called Britannia. But modern scholarly consensus ascribes De Mundo not to Aristotle but to Pseudo-Aristotle, i.e. it was written in the Graeco-Roman period or afterwards. The word Albion or insula Albionum has two possible origins, it either derives from a cognate of the Latin albus meaning white, a reference to the white cliffs of Dover or from the phrase the "island of the Albiones" in the now lost Massaliote Periplus, attested through Avienus' Ora Maritima to which the former served as a source. Albion is now applied to England in a more poetic capacity. Another romantic name for England is Loegria, related to the Welsh word for England and made popular by its use in Arthurian legend; the earliest known evidence of human presence in the area now known as England was that of Homo antecessor, dating to approximate
The Chalk Group is the lithostratigraphic unit which contains the Late Cretaceous limestone succession in southern and eastern England. The same or similar rock sequences occur across the wider northwest European chalk'province', it is characterised by thick deposits of chalk, a soft porous white limestone, deposited in a marine environment. Chalk is a limestone. A biomicrite is a limestone composed of fossil calcium carbonate mud. Most of the fossil debris in chalk consists of the microscopic plates, which are called coccoliths, of microscopic green algae known as coccolithophores. In addition to the coccoliths, the fossil debris includes a variable, but minor, percentage of the fragments of foraminifera and mollusks; the coccolithophores lived in the upper part of the water column. When they died, the microscopic calcium carbonate plates, which formed their shells settled downward through the ocean water and accumulated on the ocean bottom to form a thick layer of calcareous ooze, which became the Chalk Group.
The Chalk Group shows few signs of bedding, other than lines of flint nodules which become common in the upper part. Nodules of the mineral pyrite occur and are oxidized to brown iron oxide on exposed surfaces. Well-known outcrops include the White Cliffs of Dover, Beachy Head, the southern coastal cliffs of the Isle of Wight and the quarries and motorway cuttings at Blue Bell Hill, at the Stokenchurch Gap on the Oxfordshire/Buckinghamshire border where the M40 motorway cuts through the Aston Rowant National Nature Reserve; the Chalk Group is now divided into a White Chalk Subgroup and a Grey Chalk Subgroup, both of which are further subdivided into formations. These modern divisions replace numerous earlier divisions, references to which occur on geological maps and in other geological literature. No subgroups were defined but three formations were identified. Different formations are defined within the'northern' and'southern' provinces, from Norfolk northwards and south of the Thames valley respectively.
A'transitional province' between the two and covering much of East Anglia and the Chiltern Hills is recognised. A different approach again is taken; the Grey Chalk Subgroup is relatively soft and greyish in colour. It is the most fossiliferous; the strata of this subgroup begin with the'Glauconitic Marl Member', named after the grains of the green minerals glauconite and chlorite which it contains. The remainder of the subgroup is argillaceous in its lower part (the West Melbury Marly Chalk Formation and becomes progressively purer in the'Zig-zag Chalk Formation'. In the central Chilterns the two parts are separated by the hard Totternhoe Stone, which forms a prominent scarp in some places. There are few, if any, flint nodules present; these two formations are not recognised within the northern province i.e. the outcrop north from East Anglia to Yorkshire, where the entire sequence is now referred to as the'Ferriby Chalk Formation'. The thickness of the Grey Chalk Subgroup strata varies, averaging around 200 ft, depending upon the location.
They contains fossils such as the ammonites Schloenbachia and Mantelliceras, the belemnite Actinocamax, the bivalves Inoceramus and Ostrea. The White Chalk Subgroup includes what were designated the Middle Chalk and Upper Chalk Formations, together with the Plenus Marls. In the southern province it is divided in the following way: Portsdown Chalk Formation Culver Chalk Formation Spetisbury Chalk Member Tarrant Chalk Member Newhaven Chalk Formation Seaford Chalk Formation Lewes Nodular Chalk Formation New Pit Chalk Formation Holywell Nodular Chalk Formation Plenus Marls MemberIn the northern province the sequence is divided thus: Rowe Chalk Formation Flamborough Chalk Formation Burnham Chalk Formation Welton Chalk Formation Plenus Marls MemberIn the southern province, the former Middle Chalk, now the Holywell Nodular Chalk Formation and overlying New Pit Formation, averages about 200 ft in thickness; the sparse fossils found in this sequence include the brachiopod Terebratulina and the echinoid Conulus.
The former Upper Chalk by comparison is softer than the underlying sequence and the flint nodules it contains are far more abundant in the South of England, although in Yorkshire the underlying strata have the highest concentration of flints. It may contain gastropod fossils in some nodular layers; the thickness of this sequence varies often averaging around 300 ft. Fossils may be abundant and include the bivalve Spondylus, the brachiopods Terebratulina and Gibbithyris, the echinoids Sternotaxis, Micraster and Tylocidaris, the crinoid Marsupites, the small sponge Porosphaera
Ornithischia is an extinct clade of herbivorous dinosaurs characterized by a pelvic structure similar to that of birds. The name Ornithischia, or "bird-hipped", reflects this similarity and is derived from the Greek stem ornith-, meaning "of a bird", ischion, plural ischia, meaning "hip joint". However, birds are only distantly related to this group. Ornithischians with well known anatomical adaptations include the ceratopsians or "horn-faced" dinosaurs, armored dinosaurs such as stegosaurs and ankylosaurs, pachycephalosaurids and the ornithopods. There is strong evidence that certain groups of ornithischians lived in herds segregated by age group, with juveniles forming their own flocks separate from adults; some were at least covered in filamentous pelts, there is much debate over whether these filaments found in specimens of Tianyulong and Kulindadromeus may have been primitive feathers. In 1887, Harry Seeley divided Dinosauria into two clades: Saurischia. Ornithischia is a supported clade with an abundance of diagnostic characters.
The two most notable traits are a "bird-like" hip and beak-like predentary structure, though they shared other features as well. The ornithischian pelvis was "opisthopubic", meaning that the pubis pointed down and backwards, parallel with the ischium. Additionally, the ilium had a forward-pointing process to support the abdomen; this resulted in a four-pronged pelvic structure. In contrast to this, the saurischian pelvis was "propubic", meaning the pubis pointed toward the head, as in ancestral reptiles; the opisthopubic pelvis independently evolved at least three times in dinosaurs. Some argue that the opisthopubic pelvis evolved a fourth time, in the clade Dromaeosauridae, but this is controversial, as other authors argue that dromaeosaurids are mesopubic. Ornithischians shared; this unpaired bone was situated at the front of the lower jaw. The predentary coincided with the premaxilla in the upper jaw. Together, they formed a beak-like apparatus used to clip off plant material. In ceratopsian dinosaurs, it opposed the rostral bone.
In 2017 Baron & Barrett suggested that Chilesaurus may represent an early diverging ornithischian that had not yet acquired the predentary of all other ornithischians. Ornithischians had paired premaxillary bones that were toothless and roughened at the tip of the snout. Ornithischians developed a narrow "eyebrow", or palpebral bone, across the outside of the eye socket. Ornithischians had reduced, or closed-off, antorbital fenestrae. Ornithischian jaw joints were lowered below the level of the teeth, bringing the teeth into simultaneous occlusion. Ornithischians had "leaf-shaped" cheek teeth. Ornithischian backbones were stiffened near the pelvis by the ossification of tendons above the sacrum. Additionally, ornithischians had at least five sacral vertebrae attaching to the pelvis. Ornithischia is a branch-based taxon defined as all dinosaurs more related to Triceratops horridus Marsh, 1889 than to either Passer domesticus or Saltasaurus loricatus Bonaparte & Powell, 1980. Genasauria comprises the clades Neornithischia.
Thyreophora includes Ankylosauria. Neornithischia comprises several basal taxa and Ornithopoda. Cerapoda is a recent concept; the cladogram below follows a 2009 analysis by colleagues. All tested. Cladogram after Butler et al. 2011. Ornithopoda includes Hypsilophodon and others; the exact placement of Ornithischia within the dinosaur lineage is a contentious issue. Traditionally, Ornithischia is considered the sister group of Saurischia. However, in the alternative hypothesis of dinosaur relationships, proposed by Baron, Norman & Barrett in the journal Nature in 2017, Ornithischia was recovered as the sister group to the Theropoda, which grouped together in the clade Ornithoscelida; this hypothesis was challenged by an international consortium of early dinosaur experts led by Max Langer. However, the data that supported the more traditional placement of Ornithischia, as sister taxon of Saurischia, was found not to be statistically significant from the evidence that supported the Ornithoscelida hypothesis, in both the study by Langer et al. and the reply to the study by Baron et al.
A further 2017 study found some support for the abandoned Phytodinosauria model, which classifies ornithischians together with sauropodomorphs. Ornithischians shifted from bipedal to quadrupedal posture at least three times in their evolutionary history and it has been shown primitive members may have been capable of both forms of movement. Most ornithischians were herbivorous. In fact, most of the unifying characters of Ornithischia are thought to be related to this herbivory. For example, the shift to an opisthopubic pelvis is thought to be related to the development of a large stomach or stomachs and gut which would allow ornithischians to digest plant matter better; the smallest known ornithischian is Fruitadens haagarorum. The largest Fruitadens individuals reached just 65–75 cm. Only carnivorous, sa
Nodosauridae is a family of ankylosaurian dinosaurs, from the Late Jurassic to the Late Cretaceous Period of what are now Americas, Europe and Antarctica. Nodosaurids, like their close relatives the ankylosaurids, were armored dinosaurs adorned with rows of bony armor nodules and spines which were covered in keratin sheaths. All nodosaurids, like other ankylosaurians, were medium-sized to large built quadrupedal herbivorous dinosaurs, possessing small leaf-shaped teeth. Unlike ankylosaurids, nodosaurids lacked mace-like tail clubs. Many nodosaurids had spikes projecting outward from their shoulders. One well-preserved nodosaurid "mummy", known as the Suncor nodosaur, preserved a nearly complete set of armor in life position, as well as the keratin covering and mineralized remains of the underlying skin which indicate the animal had red and white camouflage; the family Nodosauridae was erected by Othniel Charles Marsh in 1890, anchored on the genus Nodosaurus. The clade Nodosauridae was first defined by Paul Sereno in 1998 as "all ankylosaurs closer to Panoplosaurus than to Ankylosaurus," a definition followed by Vickaryous, Teresa Maryańska, Weishampel in 2004.
Vickaryous et al. considered two genera of nodosaurids to be of uncertain placement: Struthiosaurus and Animantarx, considered the most primitive member of the Nodosauridae to be Cedarpelta. The cladogram below follows the most resolved topology from a 2011 analysis by paleontologists Richard S. Thompson, Jolyon C. Parish, Susannah C. R. Maidment and Paul M. Barrett; the placement of Polacanthinae follows its original definition by Kenneth Carpenter in 2001. The near simultaneous appearance of nodosaurids in both North America and Europe is worthy of consideration. Europelta is the oldest nodosaurid from Europe, it is derived from the lower Albian Escucha Formation; the oldest western North American nodosaurid is Sauropelta, from the lower Albian Little Sheep Mudstone Member of the Cloverly Formation, at an age of 108.5±0.2 million years. Eastern North American fossils seem older. Teeth of Priconodon crassus from the Arundel Clay of the Potomac Group of Maryland, which dates near the Aptian–Albian boundary.
The Propanoplosaurus hatchling from the base of the underlying Patuxent Formation, dating to the upper Aptian, is the oldest known nodosaurid. Polacanthids are known from pre-Aptian fauna from both North America; the timing of the appearance of nodosaurids on both continents indicates that the origins of the clade preceded the isolation of North America and Europe, pushing the group's date of evolution back to at least the "middle" Aptian. The separation of Nodosauridae into European Struthiosaurinae and North American Nodosaurinae by the end of the Aptian provides a revised date for the isolation of the continents from each other by rising sealevels. Below is a table showing the age difference between continents. North American nodosaurids are teal, European nodosaurids are green, European polacanthids are blue, North American polacanthids are brown. Other nodosaurids or polacanthids are black; this table supports the observations by Kirkland et al.. James Kirkland et al. considers Mymoorapelta, Hylaeosaurus, Polacanthus and Gastonia to be Polacanthids, outside of Nodosauridae.
Timeline of ankylosaur research Carpenter, K.. "Phylogenetic analysis of the Ankylosauria." In Carpenter, K. 2001: The Armored Dinosaurs. Indiana University Press, Bloomington & Indianapolis, 2001, pp. xv-526 Osi, Attila. Hungarosaurus tormai, a new ankylosaur from the Upper Cretaceous of Hungary. Journal of Vertebrate Paleontology 25:370-383, June 2003. Alberta oilsands discovery of 2011
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago, although the exact origin and timing of the evolution of dinosaurs is the subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201 million years ago. Reverse genetic engineering and the fossil record both demonstrate that birds are modern feathered dinosaurs, having evolved from earlier theropods during the late Jurassic Period; as such, birds were the only dinosaur lineage to survive the Cretaceous–Paleogene extinction event 66 million years ago. Dinosaurs can therefore be divided into birds; this article deals with non-avian dinosaurs. Dinosaurs are a varied group of animals from taxonomic and ecological standpoints. Birds, at over 10,000 living species, are the most diverse group of vertebrates besides perciform fish. Using fossil evidence, paleontologists have identified over 500 distinct genera and more than 1,000 different species of non-avian dinosaurs.
Dinosaurs are represented on every continent by fossil remains. Through the first half of the 20th century, before birds were recognized to be dinosaurs, most of the scientific community believed dinosaurs to have been sluggish and cold-blooded. Most research conducted since the 1970s, has indicated that all dinosaurs were active animals with elevated metabolisms and numerous adaptations for social interaction; some were herbivorous, others carnivorous. Evidence suggests that egg-laying and nest-building are additional traits shared by all dinosaurs and non-avian alike. While dinosaurs were ancestrally bipedal, many extinct groups included quadrupedal species, some were able to shift between these stances. Elaborate display structures such as horns or crests are common to all dinosaur groups, some extinct groups developed skeletal modifications such as bony armor and spines. While the dinosaurs' modern-day surviving avian lineage are small due to the constraints of flight, many prehistoric dinosaurs were large-bodied—the largest sauropod dinosaurs are estimated to have reached lengths of 39.7 meters and heights of 18 meters and were the largest land animals of all time.
Still, the idea that non-avian dinosaurs were uniformly gigantic is a misconception based in part on preservation bias, as large, sturdy bones are more to last until they are fossilized. Many dinosaurs were quite small: Xixianykus, for example, was only about 50 cm long. Since the first dinosaur fossils were recognized in the early 19th century, mounted fossil dinosaur skeletons have been major attractions at museums around the world, dinosaurs have become an enduring part of world culture; the large sizes of some dinosaur groups, as well as their monstrous and fantastic nature, have ensured dinosaurs' regular appearance in best-selling books and films, such as Jurassic Park. Persistent public enthusiasm for the animals has resulted in significant funding for dinosaur science, new discoveries are covered by the media; the taxon'Dinosauria' was formally named in 1841 by paleontologist Sir Richard Owen, who used it to refer to the "distinct tribe or sub-order of Saurian Reptiles" that were being recognized in England and around the world.
The term is derived from Ancient Greek δεινός, meaning'terrible, potent or fearfully great', σαῦρος, meaning'lizard or reptile'. Though the taxonomic name has been interpreted as a reference to dinosaurs' teeth and other fearsome characteristics, Owen intended it to evoke their size and majesty. Other prehistoric animals, including pterosaurs, ichthyosaurs and Dimetrodon, while popularly conceived of as dinosaurs, are not taxonomically classified as dinosaurs. Pterosaurs are distantly related to dinosaurs; the other groups mentioned are, like dinosaurs and pterosaurs, members of Sauropsida, except Dimetrodon. Under phylogenetic nomenclature, dinosaurs are defined as the group consisting of the most recent common ancestor of Triceratops and Neornithes, all its descendants, it has been suggested that Dinosauria be defined with respect to the MRCA of Megalosaurus and Iguanodon, because these were two of the three genera cited by Richard Owen when he recognized the Dinosauria. Both definitions result in the same set of animals being defined as dinosaurs: "Dinosauria = Ornithischia + Saurischia", encompassing ankylosaurians, ceratopsians, ornithopods and sauropodomorphs.
Birds are now recognized as being the sole surviving lineage of theropod dinosaurs. In traditional taxonomy, birds were considered a separate class that had evolved from dinosaurs, a distinct superorder. However, a majority of contemporary paleontologists concerned with dinosaurs reject the traditional style of classification in favor of phylogenetic taxonomy. Birds are thus considered to be dinosaurs and dinosaurs are, not extinct. Birds are classified as belonging to the subgroup M
The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 mya. It is the last period of the Mesozoic Era, the longest period of the Phanerozoic Eon; the Cretaceous Period is abbreviated K, for its German translation Kreide. The Cretaceous was a period with a warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas; these oceans and seas were populated with now-extinct marine reptiles and rudists, while dinosaurs continued to dominate on land. During this time, new groups of mammals and birds, as well as flowering plants, appeared; the Cretaceous ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs and large marine reptiles died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary, a geologic signature associated with the mass extinction which lies between the Mesozoic and Cenozoic eras.
The Cretaceous as a separate period was first defined by Belgian geologist Jean d'Omalius d'Halloy in 1822, using strata in the Paris Basin and named for the extensive beds of chalk, found in the upper Cretaceous of Western Europe. The name Cretaceous was derived from Latin creta; the Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series. In older literature the Cretaceous is sometimes divided into three series: Neocomian and Senonian. A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide. In many parts of the world, alternative local subdivisions are still in use; as with other older geologic periods, the rock beds of the Cretaceous are well identified but the exact age of the system's base is uncertain by a few million years. No great extinction or burst of diversity separates the Cretaceous from the Jurassic. However, the top of the system is defined, being placed at an iridium-rich layer found worldwide, believed to be associated with the Chicxulub impact crater, with its boundaries circumscribing parts of the Yucatán Peninsula and into the Gulf of Mexico.
This layer has been dated at 66.043 Ma. A 140 Ma age for the Jurassic-Cretaceous boundary instead of the accepted 145 Ma was proposed in 2014 based on a stratigraphic study of Vaca Muerta Formation in Neuquén Basin, Argentina. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a "first step" toward formally changing the age in the International Union of Geological Sciences. From youngest to oldest, the subdivisions of the Cretaceous period are: Late Cretaceous Maastrichtian – Campanian – Santonian – Coniacian – Turonian – Cenomanian – Early Cretaceous Albian – Aptian – Barremian – Hauterivian – Valanginian – Berriasian – The high sea level and warm climate of the Cretaceous meant large areas of the continents were covered by warm, shallow seas, providing habitat for many marine organisms; the Cretaceous was named for the extensive chalk deposits of this age in Europe, but in many parts of the world, the deposits from the Cretaceous are of marine limestone, a rock type, formed under warm, shallow marine circumstances.
Due to the high sea level, there was extensive space for such sedimentation. Because of the young age and great thickness of the system, Cretaceous rocks are evident in many areas worldwide. Chalk is a rock type characteristic for the Cretaceous, it consists of coccoliths, microscopically small calcite skeletons of coccolithophores, a type of algae that prospered in the Cretaceous seas. In northwestern Europe, chalk deposits from the Upper Cretaceous are characteristic for the Chalk Group, which forms the white cliffs of Dover on the south coast of England and similar cliffs on the French Normandian coast; the group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not consolidated and the Chalk Group still consists of loose sediments in many places; the group has other limestones and arenites. Among the fossils it contains are sea urchins, belemnites and sea reptiles such as Mosasaurus. In southern Europe, the Cretaceous is a marine system consisting of competent limestone beds or incompetent marls.
Because the Alpine mountain chains did not yet exist in the Cretaceous, these deposits formed on the southern edge of the European continental shelf, at the margin of the Tethys Ocean. Stagnation of deep sea currents in middle Cretaceous times caused anoxic conditions in the sea water leaving the deposited organic matter undecomposed. Half the worlds petroleum reserves were laid down at this time in the anoxic conditions of what would become the Persian Gulf and the Gulf of Mexico. In many places around the world, dark anoxic shales were formed during this interval; these shales are an important source rock for oil and gas, for example in the subsurface of the North Sea. During th
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals have mouthparts adapted to rasping or grinding. Horses and other herbivores have wide flat teeth that are adapted to grinding grass, tree bark, other tough plant material. A large percentage of herbivores have mutualistic gut flora that help them digest plant matter, more difficult to digest than animal prey; this flora is made up of cellulose-digesting bacteria. Herbivore is the anglicized form of a modern Latin coinage, cited in Charles Lyell's 1830 Principles of Geology. Richard Owen employed the anglicized term in an 1854 work on fossil skeletons. Herbivora is derived from the Latin herba meaning a small plant or herb, vora, from vorare, to eat or devour. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants and photosynthesizing bacteria.
More organisms that feed on autotrophs in general are known as primary consumers. Herbivory is limited to animals that eat plants. Fungi and protists that feed on living plants are termed plant pathogens, while fungi and microbes that feed on dead plants are described as saprotrophs. Flowering plants that obtain nutrition from other living plants are termed parasitic plants. There is, however, no single exclusive and definitive ecological classification of consumption patterns. In zoology, an herbivore is an animal, adapted to eat plant matter. Our understanding of herbivory in geological time comes from three sources: fossilized plants, which may preserve evidence of defence, or herbivory-related damage. Although herbivory was long thought to be a Mesozoic phenomenon, fossils have shown that within less than 20 million years after the first land plants evolved, plants were being consumed by arthropods. Insects fed on the spores of early Devonian plants, the Rhynie chert provides evidence that organisms fed on plants using a "pierce and suck" technique.
During the next 75 million years, plants evolved a range of more complex organs, such as roots and seeds. There is no evidence of any organism being fed upon until the middle-late Mississippian, 330.9 million years ago. There was a gap of 50 to 100 million years between the time each organ evolved and the time organisms evolved to feed upon them. Further than their arthropod status, the identity of these early herbivores is uncertain. Hole feeding and skeletonisation are recorded in the early Permian, with surface fluid feeding evolving by the end of that period. Herbivory among four-limbed terrestrial vertebrates, the tetrapods developed in the Late Carboniferous. Early tetrapods were large amphibious piscivores. While amphibians continued to feed on fish and insects, some reptiles began exploring two new food types and plants; the entire dinosaur order ornithischia was composed with herbivores dinosaurs. Carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation.
In contrast, a complex set of adaptations was necessary for feeding on fibrous plant materials. Arthropods evolved herbivory in four phases, changing their approach to it in response to changing plant communities. Tetrapod herbivores made their first appearance in the fossil record of their jaws near the Permio-Carboniferous boundary 300 million years ago; the earliest evidence of their herbivory has been attributed to dental occlusion, the process in which teeth from the upper jaw come in contact with teeth in the lower jaw is present. The evolution of dental occlusion led to a drastic increase in plant food processing and provides evidence about feeding strategies based on tooth wear patterns. Examination of phylogenetic frameworks of tooth and jaw morphologes has revealed that dental occlusion developed independently in several lineages tetrapod herbivores; this suggests that evolution and spread occurred within various lineages. Herbivores form an important link in the food chain because they consume plants in order to digest the carbohydrates photosynthetically produced by a plant.
Carnivores in turn consume herbivores for the same reason, while omnivores can obtain their nutrients from either plants or animals. Due to a herbivore's ability to survive on tough and fibrous plant matter, they are termed the primary consumers in the food cycle. Herbivory and omnivory can be regarded as special cases of Consumer-Resource Systems. Herbivores come in all sizes in the animal kingdom, they include aquatic and non-aquatic vertebrates. They can be large, like an elephant. Many herbivores found living in close proximity to humans, such as rodents, cows and camels. Two herbivore feeding strategies are browsing. For a terrestrial mammal to be called a grazer, at least 90% of the forage has to be grass, for a browser at least 90% tree leaves and/or twigs. An intermediate feeding strategy is called "mixed-feeding". In their daily need to take up energy from forage, herbivores of different body mass may be selective in choosing their food. "Selective" means that herbivores may choose their forage source depending on, e.g. season or food avail