Pakistan the Islamic Republic of Pakistan, is a country in South Asia. It is the world’s sixth-most populous country with a population exceeding 212,742,631 people. In area, it is the 33rd-largest country. Pakistan has a 1,046-kilometre coastline along the Arabian Sea and Gulf of Oman in the south and is bordered by India to the east, Afghanistan to the west, Iran to the southwest, China in the far northeast, it is separated narrowly from Tajikistan by Afghanistan's Wakhan Corridor in the northwest, shares a maritime border with Oman. The territory that now constitutes Pakistan was the site of several ancient cultures and intertwined with the history of the broader Indian subcontinent; the ancient history involves the Neolithic site of Mehrgarh and the Bronze Age Indus Valley Civilisation, was home to kingdoms ruled by people of different faiths and cultures, including Hindus, Indo-Greeks, Turco-Mongols and Sikhs. The area has been ruled by numerous empires and dynasties, including the Persian Achaemenid Empire, Alexander III of Macedon, the Seleucid Empire, the Indian Maurya Empire, the Gupta Empire, the Arab Umayyad Caliphate, the Delhi Sultanate, the Mongol Empire, the Mughal Empire, the Afghan Durrani Empire, the Sikh Empire and, most the British Empire.
Pakistan is the only country to have been created in the name of Islam. It is an ethnically and linguistically diverse country, with a diverse geography and wildlife. A dominion, Pakistan adopted a constitution in 1956, becoming an Islamic republic. An ethnic civil war and Indian military intervention in 1971 resulted in the secession of East Pakistan as the new country of Bangladesh. In 1973, Pakistan adopted a new constitution which stipulated that all laws are to conform to the injunctions of Islam as laid down in the Quran and Sunnah. A regional and middle power, Pakistan has the sixth-largest standing armed forces in the world and is a nuclear power as well as a declared nuclear-weapons state, the second in South Asia and the only nation in the Muslim world to have that status. Pakistan has a semi-industrialised economy with a well-integrated agriculture sector and a growing services sector, it is ranked among the emerging and growth-leading economies of the world, is backed by one of the world's largest and fastest-growing middle class.
Pakistan's political history since independence has been characterized by periods of military rule, political instability and conflicts with India. The country continues to face challenging problems, including overpopulation, poverty and corruption. Pakistan is a member of the UN, the Shanghai Cooperation Organisation, the OIC, the Commonwealth of Nations, the SAARC and the Islamic Military Counter Terrorism Coalition; the name Pakistan means "land of the pure" in Urdu and Persian. It alludes to the word pāk meaning pure in Pashto; the suffix ـستان is a Persian word meaning the place of, recalls the synonymous Sanskrit word sthāna स्थान. The name of the country was coined in 1933 as Pakstan by Choudhry Rahmat Ali, a Pakistan Movement activist, who published it in his pamphlet Now or Never, using it as an acronym referring to the names of the five northern regions of British India: Punjab, Kashmir and Baluchistan; the letter i was incorporated to ease pronunciation. Some of the earliest ancient human civilisations in South Asia originated from areas encompassing present-day Pakistan.
The earliest known inhabitants in the region were Soanian during the Lower Paleolithic, of whom stone tools have been found in the Soan Valley of Punjab. The Indus region, which covers most of present day Pakistan, was the site of several successive ancient cultures including the Neolithic Mehrgarh and the Bronze Age Indus Valley Civilisation at Harappa and Mohenjo-Daro; the Vedic period was characterised by an Indo-Aryan culture. Multan was an important Hindu pilgrimage centre; the Vedic civilisation flourished in the ancient Gandhāran city of Takṣaśilā, now Taxila in the Punjab, founded around 1000 BCE. Successive ancient empires and kingdoms ruled the region: the Persian Achaemenid Empire, Alexander the Great's empire in 326 BCE and the Maurya Empire, founded by Chandragupta Maurya and extended by Ashoka the Great, until 185 BCE; the Indo-Greek Kingdom founded by Demetrius of Bactria included Gandhara and Punjab and reached its greatest extent under Menander, prospering the Greco-Buddhist culture in the region.
Taxila had one of the earliest universities and centres of higher education in the world, established during the late Vedic period in 6th century BCE. The school consisted of several monasteries without large dormitories or lecture halls where the religious instruction was provided on an individualistic basis; the ancient university was documented by the invading forces of Alexander the Great, "the like of which had not been seen in Greece," and was recorded by Chinese pilgrims in the 4th or 5th century CE. At its zenith, the Rai Dynasty of Sindh ruled the surrounding territories; the Pala Dynasty was the last Buddhist empire, under Dharmapala and Devapala, stretched across South Asia from what is now Bangladesh through Northern India to Pakistan. The Arab conqueror Muhammad bin Qasim conquered Sindh in 711 CE; the Pakistan government's official chronol
The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.2 million years from the end of the Cambrian Period 485.4 million years ago to the start of the Silurian Period 443.8 Mya. The Ordovician, named after the Celtic tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same rock beds in northern Wales into the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed strata were different from those of either the Cambrian or the Silurian systems, placed them in a system of their own; the Ordovician received international approval in 1960, when it was adopted as an official period of the Paleozoic Era by the International Geological Congress. Life continued to flourish during the Ordovician as it did in the earlier Cambrian period, although the end of the period was marked by the Ordovician–Silurian extinction events.
Invertebrates, namely molluscs and arthropods, dominated the oceans. The Great Ordovician Biodiversification Event increased the diversity of life. Fish, the world's first true vertebrates, continued to evolve, those with jaws may have first appeared late in the period. Life had yet to diversify on land. About 100 times as many meteorites struck the Earth per year during the Ordovician compared with today; the Ordovician Period began with a major extinction called the Cambrian–Ordovician extinction event, about 485.4 Mya. It lasted for about 42 million years and ended with the Ordovician–Silurian extinction events, about 443.8 Mya which wiped out 60% of marine genera. The dates given are recent radiometric dates and vary from those found in other sources; this second period of the Paleozoic era created abundant fossils that became major petroleum and gas reservoirs. The boundary chosen for the beginning of both the Ordovician Period and the Tremadocian stage is significant, it correlates well with the occurrence of widespread graptolite and trilobite species.
The base of the Tremadocian allows scientists to relate these species not only to each other, but to species that occur with them in other areas. This makes it easier to place many more species in time relative to the beginning of the Ordovician Period. A number of regional terms have been used to subdivide the Ordovician Period. In 2008, the ICS erected a formal international system of subdivisions. There exist Baltoscandic, Siberian, North American, Chinese Mediterranean and North-Gondwanan regional stratigraphic schemes; the Ordovician Period in Britain was traditionally broken into Early and Late epochs. The corresponding rocks of the Ordovician System are referred to as coming from the Lower, Middle, or Upper part of the column; the faunal stages from youngest to oldest are: Late Ordovician Hirnantian/Gamach Rawtheyan/Richmond Cautleyan/Richmond Pusgillian/Maysville/Richmond Middle Ordovician Trenton Onnian/Maysville/Eden Actonian/Eden Marshbrookian/Sherman Longvillian/Sherman Soudleyan/Kirkfield Harnagian/Rockland Costonian/Black River Chazy Llandeilo Whiterock Llanvirn Early Ordovician Cassinian Arenig/Jefferson/Castleman Tremadoc/Deming/Gaconadian The Tremadoc corresponds to the Tremadocian.
The Floian corresponds to the lower Arenig. The Llanvirn occupies the rest of the Darriwilian, terminates with it at the base of the Late Ordovician; the Sandbian represents the first half of the Caradoc. During the Ordovician, the southern continents were collected into Gondwana. Gondwana started the period in equatorial latitudes and, as the period progressed, drifted toward the South Pole. Early in the Ordovician, the continents of Laurentia and Baltica were still independent continents, but Baltica began to move towards Laurentia in the period, causing the Iapetus Ocean between them to shrink; the small continent Avalonia separated from Gondwana and began to move north towards Baltica and Laurentia, opening the Rheic Ocean between Gondwana and Avalonia. The Taconic orogeny, a major mountain-building episode, was well under way in Cambrian times. In the early and middle Ordovician, temperatures were mild, but at the beginning of the Late Ordovician, from 460 to 450 Ma, volcanoes along the margin of the Iapetus Ocean spewed massive amounts of carbon dioxide, a greenhouse gas, into the atmosphere, turning the planet into a hothouse.
Sea levels were high, but as Gondwana moved south, ice accumulated into glaciers and sea levels dropped. At first, low-lying sea beds increased diversity, but glaciation led to mass extinctions as the seas drained and continental shelves became dry land. During the Ordovician, in fact during the Tremadocian, marine transgressions worldwide were the greatest for which evidence is preserved; these volcanic island arcs collided with proto North America to form the Appalachian mountains. By the end of the Late Ordovician the volcanic emissions had stopped. Gondwana had by that time neared the South Pole and was glaciated
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
The Jurassic period was a geologic period and system that spanned 56 million years from the end of the Triassic Period 201.3 million years ago to the beginning of the Cretaceous Period 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era known as the Age of Reptiles; the start of the period was marked by the major Triassic–Jurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian-Toarcian extinction in the Early Jurassic, the Tithonian event at the end; the Jurassic period is divided into three epochs: Early and Late. In stratigraphy, the Jurassic is divided into the Lower Jurassic, Middle Jurassic, Upper Jurassic series of rock formations; the Jurassic is named after the Jura Mountains within the European Alps, where limestone strata from the period were first identified. By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north, Gondwana to the south; this created more coastlines and shifted the continental climate from dry to humid, many of the arid deserts of the Triassic were replaced by lush rainforests.
On land, the fauna transitioned from the Triassic fauna, dominated by both dinosauromorph and crocodylomorph archosaurs, to one dominated by dinosaurs alone. The first birds appeared during the Jurassic, having evolved from a branch of theropod dinosaurs. Other major events include the appearance of the earliest lizards, the evolution of therian mammals, including primitive placentals. Crocodilians made the transition from a terrestrial to an aquatic mode of life; the oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, while pterosaurs were the dominant flying vertebrates. The chronostratigraphic term "Jurassic" is directly linked to the Jura Mountains, a mountain range following the course of the France–Switzerland border. During a tour of the region in 1795, Alexander von Humboldt recognized the limestone dominated mountain range of the Jura Mountains as a separate formation that had not been included in the established stratigraphic system defined by Abraham Gottlob Werner, he named it "Jura-Kalkstein" in 1799.
The name "Jura" is derived from the Celtic root *jor via Gaulish *iuris "wooded mountain", borrowed into Latin as a place name, evolved into Juria and Jura. The Jurassic period is divided into three epochs: Early and Late. In stratigraphy, the Jurassic is divided into the Lower Jurassic, Middle Jurassic, Upper Jurassic series of rock formations known as Lias and Malm in Europe; the separation of the term Jurassic into three sections originated with Leopold von Buch. The faunal stages from youngest to oldest are: During the early Jurassic period, the supercontinent Pangaea broke up into the northern supercontinent Laurasia and the southern supercontinent Gondwana; the Jurassic North Atlantic Ocean was narrow, while the South Atlantic did not open until the following Cretaceous period, when Gondwana itself rifted apart. The Tethys Sea closed, the Neotethys basin appeared. Climates were warm, with no evidence of a glacier having appeared; as in the Triassic, there was no land over either pole, no extensive ice caps existed.
The Jurassic geological record is good in western Europe, where extensive marine sequences indicate a time when much of that future landmass was submerged under shallow tropical seas. In contrast, the North American Jurassic record is the poorest of the Mesozoic, with few outcrops at the surface. Though the epicontinental Sundance Sea left marine deposits in parts of the northern plains of the United States and Canada during the late Jurassic, most exposed sediments from this period are continental, such as the alluvial deposits of the Morrison Formation; the Jurassic was a time of calcite sea geochemistry in which low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate. Carbonate hardgrounds were thus common, along with calcitic ooids, calcitic cements, invertebrate faunas with dominantly calcitic skeletons; the first of several massive batholiths were emplaced in the northern American cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny. Important Jurassic exposures are found in Russia, South America, Japan and the United Kingdom.
In Africa, Early Jurassic strata are distributed in a similar fashion to Late Triassic beds, with more common outcrops in the south and less common fossil beds which are predominated by tracks to the north. As the Jurassic proceeded and more iconic groups of dinosaurs like sauropods and ornithopods proliferated in Africa. Middle Jurassic strata are neither well studied in Africa. Late Jurassic strata are poorly represented apart from the spectacular Tendaguru fauna in Tanzania; the Late Jurassic life of Tendaguru is similar to that found in western North America's Morrison Formation. During the Jurassic period, the primary vertebrates living in the sea were marine reptiles; the latter include ichthyosaurs, which were at the peak of their diversity, plesiosaurs and marine crocodiles of the families Teleosauridae and Metriorhynchidae. Numerous turtles could be found in rivers. In the invertebrate world, several new groups appeared, including rudists (a reef-formi
A chordate is an animal constituting the phylum Chordata. During some period of their life cycle, chordates possess a notochord, a dorsal nerve cord, pharyngeal slits, an endostyle, a post-anal tail: these five anatomical features define this phylum. Chordates are bilaterally symmetric; the Chordata and Ambulacraria together form the superphylum Deuterostomia. Chordates are divided into three subphyla: Vertebrata. There are extinct taxa such as the Vetulicolia. Hemichordata has been presented as a fourth chordate subphylum, but now is treated as a separate phylum: hemichordates and Echinodermata form the Ambulacraria, the sister phylum of the Chordates. Of the more than 65,000 living species of chordates, about half are bony fish that are members of the superclass Osteichthyes. Chordate fossils have been found from as early as the Cambrian explosion, 541 million years ago. Cladistically, vertebrates - chordates with the notochord replaced by a vertebral column during development - are considered to be a subgroup of the clade Craniata, which consists of chordates with a skull.
The Craniata and Tunicata compose the clade Olfactores. Chordates form a phylum of animals that are defined by having at some stage in their lives all of the following anatomical features: A notochord, a stiff rod of cartilage that extends along the inside of the body. Among the vertebrate sub-group of chordates the notochord develops into the spine, in wholly aquatic species this helps the animal to swim by flexing its tail. A dorsal neural tube. In fish and other vertebrates, this develops into the spinal cord, the main communications trunk of the nervous system. Pharyngeal slits; the pharynx is the part of the throat behind the mouth. In fish, the slits are modified to form gills, but in some other chordates they are part of a filter-feeding system that extracts particles of food from the water in which the animals live. Post-anal tail. A muscular tail that extends backwards behind the anus. An endostyle; this is a groove in the ventral wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus.
It stores iodine, may be a precursor of the vertebrate thyroid gland. There are soft constraints that separate chordates from certain other biological lineages, but are not part of the formal definition: All chordates are deuterostomes; this means. All chordates are based on a bilateral body plan. All chordates are coelomates, have a fluid filled body cavity called a coelom with a complete lining called peritoneum derived from mesoderm; the following schema is from the third edition of Vertebrate Palaeontology. The invertebrate chordate classes are from Fishes of the World. While it is structured so as to reflect evolutionary relationships, it retains the traditional ranks used in Linnaean taxonomy. Phylum Chordata †Vetulicolia? Subphylum Cephalochordata – Class Leptocardii Clade Olfactores Subphylum Tunicata – Class Ascidiacea Class Thaliacea Class Appendicularia Class Sorberacea Subphylum Vertebrata Infraphylum incertae sedis Cyclostomata Superclass'Agnatha' paraphyletic Class Myxini Class Petromyzontida or Hyperoartia Class †Conodonta Class †Myllokunmingiida Class †Pteraspidomorphi Class †Thelodonti Class †Anaspida Class †Cephalaspidomorphi Infraphylum Gnathostomata Class †Placodermi Class Chondrichthyes Class †Acanthodii Superclass Osteichthyes Class Actinopterygii Class Sarcopterygii Superclass Tetrapoda Class Amphibia Class Sauropsida Class Synapsida Craniates, one of the three subdivisions of chordates, all have distinct skulls.
They include the hagfish. Michael J. Benton commented that "craniates are characterized by their heads, just as chordates, or all deuterostomes, are by their tails". Most craniates are vertebrates; these consist of a series of bony or cartilaginous cylindrical vertebrae with neural arches that protect the spinal cord, with projections that link the vertebrae. However hagfish have incomplete braincases and no vertebrae, are therefore not regarded as vertebrates, but as members of the craniates, the group from which vertebrates are thought to have evolved; however the cladistic exclusion of hagfish from the vertebrates is controversial, as they ma
Jeffrey A. Wilson
Jeffrey A. Wilson known as "JAW" is a professor of geological sciences and assistant curator at the Museum of Paleontology at the University of Michigan, his doctoral dissertation was on sauropod evolution and phylogeny, he has continued this work in cladistic analysis and revision of the group. With Paul Sereno, he defined the clades Somphospondyli. Wilson was involved in the discovery and description of Pabwehshi pakistanensis, the first discovery of decent Cretaceous crocodylian fossil remains from the Indian subcontinent, in the discovery of Rajasaurus narmadensis, the most known theropod dinosaur from India and a member of the family Abelisauridae, description of a number of North African dinosaurs from Niger, rediscriptions of the Cretaceous sauropods Titanosaurus colberti and Nemegtosaurus, his younger brother, Dr. Gregory P. Wilson, studies Mesozoic mammals and is an assistant professor in the Department of Biology at the University of Washington, adjunct curator of vertebrate paleontology at the Burke Museum of Natural History and Culture.
Wilson, J. A. and Sereno, P. C. Higher-level phylogeny of sauropod dinosaurs. Journal of Vertebrate Paleontology, Supplement 14:52A. Wilson, J. A. & Sereno, P. C.. Early evolution and Higher-level phylogeny of sauropod dinosaurs. Society of Vertebrate Paleontology, Memoir 5, 1-68. Sereno, P. C. Beck, A. L. Dutheil, D. B. Gado, B. Larsson, H. C. E. Lyon, G. H. Marcot, J. D. Rauhut, O. W. M. Sadleir, R. W. Sidor, C. A. Varricchio, D. J. Wilson, G. P. & Wilson, J. A. 1998. A long-snouted predatory dinosaur from Africa and the evolution of spinosaurids. Science 282:1298-1302. Document in pdf format Wilson, J. A. and M. T. Carrano. Titanosaurs and the origin of'wide-gauge' trackways: a biomechanical and systematic perspective on sauropod locomotion. Paleobiology 25:252-267. Wilson, J. A. R. N. Martinez & O. Alcober.. Distal tail segment of a titanosaur from the Upper Cretaceous of Mendoza, Argentina. Journal of Vertebrate Paleontology 19:591-594. Wilson, J A.. A nomenclature for vertebral laminae in other saurischian dinosaurs.
Journal of Vertebrate Paleontology 19:639-653. Wilson, J. A; the evolution and phylogeny of sauropod dinosaurs. Ph. D. dissertation, University of Chicago, 384pp Sereno, P. C. Beck, A. L. Dutheil, D. B. Larsson, H. C. E. Lyon, G. H. Moussa, B. Sadleir, R. W. Sidor, C. A. Varricchio, D. J. Wilson, G. P. & Wilson, J. A. Cretaceous Sauropods from the Sahara and the Uneven Rate of Skeletal Evolution Among Dinosaurs, Science 286: 1342-1347 ) Wilson, J. A. Malkani, M. S. and Gingerich, P. D. New crocodyliform from the Upper Cretaceous Pab Formation of Balochistan. Contributions from the Museum of Paleontology, University of Michigan 30: 321-336. Wilson, J. A. Sauropod dinosaur phylogeny: critique and cladistic analysis, Zoological Journal of the Linnean Society 136:215-275 Wilson, J. A. and Upchurch, P A revision of Titanosaurus Lydekker, the first dinosaur genus with a "Gondwanan" distribution, Journal of Systematic Palaeontology Volume 1 Issue 3 - September 2003 Wilson, J. A. Sereno, P. C. Srivastava, S. Bhatt, D. K. Khosla, A. and Sahni, A.
A new abelisaurid from the Lameta Formation of India. Contributions from the Museum of Paleontology, University of Michigan 31:1-42 Wilson, J. A.. Redescription of the Mongolian sauropod Nemegtosaurus mongoliensis Nowinski and comments on Late Cretaceous sauropod diversity. Journal of Systematic Palaeontology 3: 283-318. (shows that Nemegtosaurus and Quaesitosaurus are related and belong to the titanosaur group, rather than the diplodocoidea. See New Nemegtosaurus paper for more. Curry Rogers, K. A. and Wilson, J. A. 2005, The Sauropods: Evolution and Paleobiology, University of California Press, Berkeley, ISBN 0-520-24623-3 Wilson, J. A. "Overview of Sauropod Phylogeny and Evolution", in The Sauropods: Evolution and Paleobiology (broad overview of phylogenetic characteristics and evolution development of the main sauropod clades phylocode-style definitions for each clade. Wilson, J. A. and Sereno, P. C. "Structure and Evolution of a Sauropod Tooth Battery" in The Sauropods: Evolution and Paleobiology
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