India known as the Republic of India, is a country in South Asia. It is the seventh largest country by area and with more than 1.3 billion people, it is the second most populous country as well as the most populous democracy in the world. Bounded by the Indian Ocean on the south, the Arabian Sea on the southwest, the Bay of Bengal on the southeast, it shares land borders with Pakistan to the west. In the Indian Ocean, India is in the vicinity of Sri Lanka and the Maldives, while its Andaman and Nicobar Islands share a maritime border with Thailand and Indonesia; the Indian subcontinent was home to the urban Indus Valley Civilisation of the 3rd millennium BCE. In the following millennium, the oldest scriptures associated with Hinduism began to be composed. Social stratification, based on caste, emerged in the first millennium BCE, Buddhism and Jainism arose. Early political consolidations took place under the Gupta empires. In the medieval era, Zoroastrianism and Islam arrived, Sikhism emerged, all adding to the region's diverse culture.
Much of the north fell to the Delhi Sultanate. The economy expanded in the 17th century in the Mughal Empire. In the mid-18th century, the subcontinent came under British East India Company rule, in the mid-19th under British Crown rule. A nationalist movement emerged in the late 19th century, which under Mahatma Gandhi, was noted for nonviolent resistance and led to India's independence in 1947. In 2017, the Indian economy was the world's sixth largest by nominal GDP and third largest by purchasing power parity. Following market-based economic reforms in 1991, India became one of the fastest-growing major economies and is considered a newly industrialised country. However, it continues to face the challenges of poverty, corruption and inadequate public healthcare. A nuclear weapons state and regional power, it has the second largest standing army in the world and ranks fifth in military expenditure among nations. India is a federal republic governed under a parliamentary system and consists of 29 states and 7 union territories.
A pluralistic and multi-ethnic society, it is home to a diversity of wildlife in a variety of protected habitats. The name India is derived from Indus, which originates from the Old Persian word Hindush, equivalent to the Sanskrit word Sindhu, the historical local appellation for the Indus River; the ancient Greeks referred to the Indians as Indoi, which translates as "The people of the Indus". The geographical term Bharat, recognised by the Constitution of India as an official name for the country, is used by many Indian languages in its variations, it is a modernisation of the historical name Bharatavarsha, which traditionally referred to the Indian subcontinent and gained increasing currency from the mid-19th century as a native name for India. Hindustan is a Middle Persian name for India, it was introduced into India by the Mughals and used since then. Its meaning varied, referring to a region that encompassed northern India and Pakistan or India in its entirety; the name may refer to either the northern part of India or the entire country.
The earliest known human remains in South Asia date to about 30,000 years ago. Nearly contemporaneous human rock art sites have been found in many parts of the Indian subcontinent, including at the Bhimbetka rock shelters in Madhya Pradesh. After 6500 BCE, evidence for domestication of food crops and animals, construction of permanent structures, storage of agricultural surplus, appeared in Mehrgarh and other sites in what is now Balochistan; these developed into the Indus Valley Civilisation, the first urban culture in South Asia, which flourished during 2500–1900 BCE in what is now Pakistan and western India. Centred around cities such as Mohenjo-daro, Harappa and Kalibangan, relying on varied forms of subsistence, the civilization engaged robustly in crafts production and wide-ranging trade. During the period 2000–500 BCE, many regions of the subcontinent transitioned from the Chalcolithic cultures to the Iron Age ones; the Vedas, the oldest scriptures associated with Hinduism, were composed during this period, historians have analysed these to posit a Vedic culture in the Punjab region and the upper Gangetic Plain.
Most historians consider this period to have encompassed several waves of Indo-Aryan migration into the subcontinent from the north-west. The caste system, which created a hierarchy of priests and free peasants, but which excluded indigenous peoples by labeling their occupations impure, arose during this period. On the Deccan Plateau, archaeological evidence from this period suggests the existence of a chiefdom stage of political organisation. In South India, a progression to sedentary life is indicated by the large number of megalithic monuments dating from this period, as well as by nearby traces of agriculture, irrigation tanks, craft traditions. In the late Vedic period, around the 6th century BCE, the small states and chiefdoms of the Ganges Plain and the north-western regions had consolidated into 16 major oligarchies and monarchies that were known as the mahajanapadas; the emerging urbanisation gave rise to non-Vedic religious movements, two of which became independent religions. Jainism came into prominence during the life of Mahavira.
Buddhism, based on the teachings of Gautama Buddha, attracted followers from all social classes excepting the middle
Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 millionths of a metre to 33.6 metres and have complex interactions with each other and their environments, forming intricate food webs. The category includes humans, but in colloquial use the term animal refers only to non-human animals; the study of non-human animals is known as zoology. Most living animal species are in the Bilateria, a clade whose members have a bilaterally symmetric body plan; the Bilateria include the protostomes—in which many groups of invertebrates are found, such as nematodes and molluscs—and the deuterostomes, containing the echinoderms and chordates.
Life forms interpreted. Many modern animal phyla became established in the fossil record as marine species during the Cambrian explosion which began around 542 million years ago. 6,331 groups of genes common to all living animals have been identified. Aristotle divided animals into those with those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between animal taxa. Humans make use of many other animal species for food, including meat and eggs. Dogs have been used in hunting, while many aquatic animals are hunted for sport.
Non-human animals have appeared in art from the earliest times and are featured in mythology and religion. The word "animal" comes from the Latin animalis, having soul or living being; the biological definition includes all members of the kingdom Animalia. In colloquial usage, as a consequence of anthropocentrism, the term animal is sometimes used nonscientifically to refer only to non-human animals. Animals have several characteristics. Animals are eukaryotic and multicellular, unlike bacteria, which are prokaryotic, unlike protists, which are eukaryotic but unicellular. Unlike plants and algae, which produce their own nutrients animals are heterotrophic, feeding on organic material and digesting it internally. With few exceptions, animals breathe oxygen and respire aerobically. All animals are motile during at least part of their life cycle, but some animals, such as sponges, corals and barnacles become sessile; the blastula is a stage in embryonic development, unique to most animals, allowing cells to be differentiated into specialised tissues and organs.
All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. During development, the animal extracellular matrix forms a flexible framework upon which cells can move about and be reorganised, making the formation of complex structures possible; this may be calcified, forming structures such as shells and spicules. In contrast, the cells of other multicellular organisms are held in place by cell walls, so develop by progressive growth. Animal cells uniquely possess the cell junctions called tight junctions, gap junctions, desmosomes. With few exceptions—in particular, the sponges and placozoans—animal bodies are differentiated into tissues; these include muscles, which enable locomotion, nerve tissues, which transmit signals and coordinate the body. There is an internal digestive chamber with either one opening or two openings. Nearly all animals make use of some form of sexual reproduction, they produce haploid gametes by meiosis.
These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement, it first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. In most cases, a third germ layer, the mesoderm develops between them; these germ layers differentiate to form tissues and organs. Repeated instances of mating with a close relative during sexual reproduction leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for avoiding close inbreeding. In some species, such as the splendid fairywren, females benefit by mating with multiple males, thus producing more offspring of higher genetic quality; some animals are capable of asexual reproduction, which results
Reginald Innes Pocock
Reginald Innes Pocock F. R. S. was a British zoologist. Pocock was born in Clifton, the fourth son of Rev. Nicholas Pocock and Edith Prichard, he began showing interest in natural history at Oxford. He received tutoring in zoology from Sir Edward Poulton, was allowed to explore comparative anatomy at the Oxford Museum, he studied biology and geology at University College, Bristol under Conwy Lloyd Morgan and William Johnson Sollas. In 1885 he became an assistant at the Natural History Museum, worked in the section of Entomology for a year, he was put in charge of the collections of Myriapoda. He was tasked with arranging the British birds collections, in the course of which he developed a lasting interest in ornithology; the 200 papers he published in his eighteen years at the museum soon brought him recognition as an authority on Arachnida and Myriapoda: he described between 300-400 species of millipede alone, described the scorpion genus Brachistosternus. In 1904 he left to become Superintendent of London Zoo, remaining so until his retirement in 1923.
He worked, as a voluntary researcher, in the British Museum, in the mammals department. He described the Leopon in a 1912 letter to The Field, based on examination of a skin sent to him by W. S. Millard, the Secretary of the Bombay Natural History Society, his brother Edward Innes Pocock played international rugby for Scotland and was part of Cecil Rhodes' Pioneer Column. His great grandfather was marine artist Captain Nicholas Pocock. Pocock, R. I.. "On some points in the morphology of the Arachnida with notes on the classification of the group". Annals and Magazine of Natural History. 6. 11: 1–19. Pocock, R. I.. The Fauna of British India, including Ceylon and Burma. Arachnida. London: Trustees of the British Museum. Pocock, R. I.. "Some new and old genera of South American Aviculariidae". The Annals and Magazine of Natural History. 7. 8: 540−555. Pocock, R. I.. "Arachnida. Scorpiones and Solifugae". Biologia Centrali-Americana: zoology and archaeology. London: R. H. Porter. Pocock, R. I.. "On some genera and species of South-American Aviculariidae".
Annals and Magazine of Natural History. 7. 11: 81–115. Pocock, R. I.. "The Classification of existing Felidae". The Annals and Magazine of Natural History. 8. XX: 329–350. Pocock, R. I.. "The Panthers and Ounces of Asia". Journal of the Bombay Natural History Society. 34: 65–82. Pocock, R. I.. "The marbled, Pardofelis marmorata and some other Oriental species, with a definition of a new genus of the Felidae". Proceedings of the Zoological Society of London. 102: 741–766. Pocock, R. I.. The Fauna of British India, including Ceylon and Burma – Mammalia. Volume 1, Primates and Carnivora. London: Trustees of the British Museum. Pocock, R. I.. Description of a new race of puma, with a note on an abnormal tooth growth in the genus; the Annals and Magazine of Natural History. 11. VI. pp. 307–313. Pocock, R. I.. The Fauna of British India, including Ceylon and Burma – Mammalia. Volume 2, Carnivora: Aeluroidea, Arctoidea. London: Trustees of the British Museum. Pocock, R. I.. Catalogue of the Genus Felis. London: Trustees of the British Museum.
Works by or about Reginald Innes Pocock at Internet Archive Works by Reginald Innes Pocock, at the Biodiversity Heritage Library
Myanmar the Republic of the Union of Myanmar and known as Burma, is a country in Southeast Asia. Myanmar is bordered by India and Bangladesh to its west and Laos to its east and China to its north and northeast. To its south, about one third of Myanmar's total perimeter of 5,876 km forms an uninterrupted coastline of 1,930 km along the Bay of Bengal and the Andaman Sea; the country's 2014 census counted the population to be 51 million people. As of 2017, the population is about 54 million. Myanmar is 676,578 square kilometres in size, its capital city is Naypyidaw, its largest city and former capital is Yangon. Myanmar has been a member of the Association of Southeast Asian Nations since 1997. Early civilisations in Myanmar included the Tibeto-Burman-speaking Pyu city-states in Upper Burma and the Mon kingdoms in Lower Burma. In the 9th century, the Bamar people entered the upper Irrawaddy valley and, following the establishment of the Pagan Kingdom in the 1050s, the Burmese language and Theravada Buddhism became dominant in the country.
The Pagan Kingdom fell. In the 16th century, reunified by the Taungoo dynasty, the country was for a brief period the largest empire in the history of Mainland Southeast Asia; the early 19th century Konbaung dynasty ruled over an area that included modern Myanmar and controlled Manipur and Assam as well. The British took over the administration of Myanmar after three Anglo-Burmese Wars in the 19th century and the country became a British colony. Myanmar was granted independence as a democratic nation. Following a coup d'état in 1962, it became a military dictatorship under the Burma Socialist Programme Party. For most of its independent years, the country has been engrossed in rampant ethnic strife and its myriad ethnic groups have been involved in one of the world's longest-running ongoing civil wars. During this time, the United Nations and several other organisations have reported consistent and systematic human rights violations in the country. In 2011, the military junta was dissolved following a 2010 general election, a nominally civilian government was installed.
This, along with the release of Aung San Suu Kyi and political prisoners, has improved the country's human rights record and foreign relations, has led to the easing of trade and other economic sanctions. There is, continuing criticism of the government's treatment of ethnic minorities, its response to the ethnic insurgency, religious clashes. In the landmark 2015 election, Aung San Suu Kyi's party won a majority in both houses. However, the Burmese military remains a powerful force in politics. Myanmar is a country rich in jade and gems, natural gas and other mineral resources. In 2013, its GDP stood at its GDP at US$221.5 billion. The income gap in Myanmar is among the widest in the world, as a large proportion of the economy is controlled by supporters of the former military government; as of 2016, Myanmar ranks 145 out of 188 countries in human development, according to the Human Development Index. Both the names Myanmar and Burma derive from the earlier Burmese Mranma, an ethnonym for the majority Bamar ethnic group, of uncertain etymology.
The terms are popularly thought to derive from "Brahma Desha" after Brahma. In 1989, the military government changed the English translations of many names dating back to Burma's colonial period or earlier, including that of the country itself: "Burma" became "Myanmar"; the renaming remains a contested issue. Many political and ethnic opposition groups and countries continue to use "Burma" because they do not recognise the legitimacy of the ruling military government or its authority to rename the country. In April 2016, soon after taking office, Aung San Suu Kyi clarified that foreigners are free to use either name, "because there is nothing in the constitution of our country that says that you must use any term in particular"; the country's official full name is the "Republic of the Union of Myanmar". Countries that do not recognise that name use the long form "Union of Burma" instead. In English, the country is popularly known as either "Burma" or "Myanmar". Both these names are derived from the name of the majority Burmese Bamar ethnic group.
Myanmar is considered to be the literary form of the name of the group, while Burma is derived from "Bamar", the colloquial form of the group's name. Depending on the register used, the pronunciation would be Myamah; the name Burma has been in use in English since the 18th century. Burma continues to be used in English by the governments of countries such as the United Kingdom. Official United States policy retains Burma as the country's name, although the State Department's website lists the country as "Burma" and Barack Obama has referred to the country by both names; the government of Canada has in the past used Burma, such as in its 2007 legislation imposing sanctions, but as of the mid-2010s uses Myanmar. The Czech Republic uses Myanmar, although its Ministry of Foreign Affairs mentions both Myanmar and Burma on its website; the United Nations uses Myanmar, as do the Association of Southeast Asian Nations, Russia, China, Bangladesh, Norway and Switzerland. Most English-speaking international news media refer to the country by the name Myanmar, including the BBC, CNN, Al Jazeera and the Australian Broadcasting Corporation /Ra
Binomial nomenclature called binominal nomenclature or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages. Such a name is called a binomen, binominal name or a scientific name; the first part of the name – the generic name – identifies the genus to which the species belongs, while the second part – the specific name or specific epithet – identifies the species within the genus. For example, humans belong within this genus to the species Homo sapiens. Tyrannosaurus rex is the most known binomial; the formal introduction of this system of naming species is credited to Carl Linnaeus beginning with his work Species Plantarum in 1753. But Gaspard Bauhin, in as early as 1623, had introduced in his book Pinax theatri botanici many names of genera that were adopted by Linnaeus; the application of binomial nomenclature is now governed by various internationally agreed codes of rules, of which the two most important are the International Code of Zoological Nomenclature for animals and the International Code of Nomenclature for algae and plants.
Although the general principles underlying binomial nomenclature are common to these two codes, there are some differences, both in the terminology they use and in their precise rules. In modern usage, the first letter of the first part of the name, the genus, is always capitalized in writing, while that of the second part is not when derived from a proper noun such as the name of a person or place. Both parts are italicized when a binomial name occurs in normal text, thus the binomial name of the annual phlox is now written as Phlox drummondii. In scientific works, the authority for a binomial name is given, at least when it is first mentioned, the date of publication may be specified. In zoology "Patella vulgata Linnaeus, 1758"; the name "Linnaeus" tells the reader who it was that first published a description and name for this species of limpet. "Passer domesticus". The original name given by Linnaeus was Fringilla domestica; the ICZN does not require that the name of the person who changed the genus be given, nor the date on which the change was made, although nomenclatorial catalogs include such information.
In botany "Amaranthus retroflexus L." – "L." is the standard abbreviation used in botany for "Linnaeus". "Hyacinthoides italica Rothm. – Linnaeus first named this bluebell species Scilla italica. The name is composed of two word-forming elements: "bi", a Latin prefix for two, "-nomial", relating to a term or terms; the word "binomium" was used in Medieval Latin to mean a two-term expression in mathematics. Prior to the adoption of the modern binomial system of naming species, a scientific name consisted of a generic name combined with a specific name, from one to several words long. Together they formed a system of polynomial nomenclature; these names had two separate functions. First, to designate or label the species, second, to be a diagnosis or description. In a simple genus, containing only two species, it was easy to tell them apart with a one-word genus and a one-word specific name; such "polynomial names" may sometimes look like binomials, but are different. For example, Gerard's herbal describes various kinds of spiderwort: "The first is called Phalangium ramosum, Branched Spiderwort.
The other... is aptly termed Phalangium Ephemerum Virginianum, Soon-Fading Spiderwort of Virginia". The Latin phrases are short descriptions, rather than identifying labels; the Bauhins, in particular Caspar Bauhin, took some important steps towards the binomial system, by pruning the Latin descriptions, in many cases to two words. The adoption by biologists of a system of binomial nomenclature is due to Swedish botanist and physician Carl von Linné, more known by his Latinized name Carl Linnaeus, it was in his 1753 Species Plantarum that he first began using a one-word "trivial name" together with a generic name in a system of binomial nomenclature. This trivial name is what is now known as specific name; the Bauhins' genus names were retained in many of these, but the descriptive part was reduced to a single word. Linnaeus's trivial names introduced an important new idea, namely that the function of a name could be to give a species a unique label; this meant. Thus Gerard's Phalangium ephemerum virginianum became Tradescantia virgi
The Bovidae are the biological family of cloven-hoofed, ruminant mammals that includes bison, African buffalo, water buffalo, wildebeest, gazelles, goats and domestic cattle. A member of this family is called a bovid. With 143 extant species and 300 known extinct species, the family Bovidae consists of eight major subfamilies apart from the disputed Peleinae and Pantholopinae; the family evolved 20 million years ago, in the early Miocene. The bovids show great variation in pelage colouration. Excepting some domesticated forms, all male bovids have two or more horns, in many species females possess horns, too; the size and shape of the horns vary but the basic structure is always one or more pairs of simple bony protrusions without branches having a spiral, twisted or fluted form, each covered in a permanent sheath of keratin. Most bovids bear 30 to 32 teeth. Most bovids are diurnal. Social activity and feeding peak during dawn and dusk. Bovids rest before dawn, during midday, after dark, they have various methods of social organisation and social behaviour, which are classified into solitary and gregarious behaviour.
Bovids use different forms of vocal and tangible communication. Most species alternately ruminate throughout the day. While small bovids forage in dense and closed habitat, larger species feed on high-fiber vegetation in open grasslands. Most bovids are polygynous. Mature bovids mate at least once a year and smaller species may mate twice. In some species, neonate bovids remain hidden for a week to two months nursed by their mothers; the greatest diversities of bovids occur in Africa. The maximum concentration of species is in the savannas of eastern Africa. Other bovid species occur in Europe and North America. Bovidae includes three of the five domesticated mammals whose use has spread outside their original ranges, namely cattle and goats. Dairy products such as milk and cheese are manufactured from domestic cattle. Bovids provide leather and wool; the name "Bovidae" was given by the British zoologist John Edward Gray in 1821. The word "Bovidae" is the combination of the prefix bov- and the suffix -idae.
The family Bovidae is placed in the order Artiodactyla. It includes 143 extant species, accounting for nearly 55% of the ungulates, 300 known extinct species. Molecular studies have supported monophyly in the family Bovidae; the number of subfamilies in Bovidae is disputed, with suggestions of as many as ten and as few as two subfamilies. However, molecular and fossil evidence indicates the existence of eight distinct subfamilies: Aepycerotinae, Antilopinae, Caprinae, Cephalophinae and Reduncinae. In addition, three extinct subfamilies are known: Hypsodontinae and the subfamily Tethytraginae, which contains Tethytragus. In 1992, Alan W. Gentry of the Natural History Museum, London divided the eight major subfamilies of Bovidae into two major clades on the basis of their evolutionary history: the Boodontia, which comprised only the Bovinae, the Aegodontia, which consisted of the rest of the subfamilies. Boodonts have somewhat primitive teeth, resembling those of oxen, whereas aegodonts have more advanced teeth like those of goats.
A controversy exists about the recognition of Peleinae and Patholopinae, comprising the genera Pelea and Pantholops as subfamilies. In 2000, American biologist George Schaller and palaeontologist Elisabeth Vrba suggested the inclusion of Pelea in Reduncinae, though the grey rhebok, the sole species of Pelea, is different from kobs and reduncines in morphology. Pantholops, earlier classified in the Antilopinae, was placed in its own subfamily, Pantholopinae; however and morphological analysis supports the inclusion of Pantholops in Caprinae. Below is a cladogram based on Gatesy et Gentry et al.. In the early Miocene, bovids giraffids; the earliest bovids, whose presence in Africa and Eurasia in the latter part of early Miocene has been ascertained, were small animals, somewhat similar to modern gazelles, lived in woodland environments. Eotragus, the earliest known bovid, weighed 18 kg and was nearly the same in size as the Thompson's gazelle. Early in their evolutionary history, the bovids split into two main clades: Boodontia and Aegodontia.
This early split between Boodontia and Aegodontia has been attributed to the continental divide between these land masses. When these continents were rejoined, this barrier was removed, either group expanded into the territory of the other; the tribes Bovini and Tragelaphini diverged in the early Miocene. Bovids are known to have reached the Americas in the Pleistocene by crossing the Bering land bridge; the present genera of Alcelaphinae appeared in the Pliocene. The extinct Alcelaphine genus Paramularius, the same in size as the hartebeest, is believed to have come into being in the Pliocene, but became extinct in the middle Pleistocene. Several genera of Hippotraginae are known
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