Johann Friedrich Gmelin
Johann Friedrich Gmelin was a German naturalist, entomologist and malacologist. Johann Friedrich Gmelin was born as the eldest son of Philipp Friedrich Gmelin in 1748 in Tübingen, he studied medicine under his father at University of Tübingen and graduated with an MD in 1768, with a thesis entitled: Irritabilitatem vegetabilium, in singulis plantarum partibus exploratam ulterioribusque experimentis confirmatam. Defended under the presidency of Ferdinand Christoph Oetinger, whom he thanks with the words Patrono et praeceptore in aeternum pie devenerando, pro summis in medicina obtinendis honoribus. In 1769, Gmelin became an adjunct professor of medicine at University of Tübingen. In 1773, he became professor of philosophy and adjunct professor of medicine at University of Göttingen, he was promoted to full professor of medicine and professor of chemistry and mineralogy in 1778. He died in 1804 in Göttingen. Johann Friedrich Gmelin published several textbooks in the fields of chemistry, pharmaceutical science and botany.
He published the 13th edition of Systema Naturae by Carl Linnaeus in 1788 and 1789. This contained descriptions and scientific names of many new species, including birds that had earlier been catalogued without a scientific name by John Latham in his A General Synopsis of Birds. Gmelin's publication is cited as the authority for over 290 bird species and a number of butterfly species. Among his students were Georg Friedrich Hildebrandt, Carl Friedrich Kielmeyer, Friedrich Stromeyer, Wilhelm August Lampadius, he was the father of Leopold Gmelin. He described the redfin pickerel in 1789. In the scientific field of herpetology, he described many new species of reptiles. In the field of malacology, he named many species of gastropods; the abbreviation "Gmel." is found. Gmelin, Johann Friedrich. Irritabilitatem vegetabilium, in singulis plantarum partibus exploratam ulterioribusque experimentis confirmatam. Thesis Tübingen. OCLC 10717434. Allgemeine Geschichte der Gifte, 2 Vol. 1776/77 Digital edition of the University and State Library Düsseldorf.
Allgemeine Geschichte der Pflanzengifte, 1777 Allgemeine Geschichte der mineralischen Gifte. Nürnberg: Raspe, 1777. Digital edition of the University and State Library Düsseldorf. Johann Friedrich Gmelins... Einleitung in die Chemie zum Gebrauch auf Universitäten. Nürnberg: Raspe, 1780. Digital edition of the University and State Library Düsseldorf. Einleitung in die Pharmacie. Nürnberg: Raspe, 1781. Digital edition of the University and State Library Düsseldorf. Beyträge zur Geschichte des teutschen Bergbaus, 1783 Ueber die neuere Entdeckungen in der Lehre von der Luft, und deren Anwendung auf Arzneikunst, in Briefen an einen Arzt, von J. F. Gmelin. 1784 Grundsätze der technischen Chemie, 1786 Caroli a Linné, equitis aurati de stella polari, … Systema naturae per regna tria naturae, secundum classes, genera, cum characteribus, synonymis, locis. Editio decima tertia, reformata. Lipsiae, Georg Emanuel Beer, 1789-1790 Grundriß der Pharmazie, 1792 Apparatus Medicaminum tam simplicium quam praeparatorum et compositorum in Praxeos Adiumentum consideratus, Ps.
2, T. 1 - Ps. 2, T. 2. 1795–1796. Digital edition of the University and State Library Düsseldorf. Geschichte der Chemie, 1799 Allgemeine Geschichte der thierischen und mineralischen Gifte, 1806 Vane-Wright, R. I. 1975. The butterflies named by J. F. Gmelin. Bulletin of the British Museum,Entomology, 32: 17-64.pdf Gmelin's chemical genealogy Johann Friedrich Gmelin at the Mathematics Genealogy Project Johann Friedrich Gmelin in the German National Library catalogue "Author Details for Johann Friedrich Gmelin". International Plant Names Index. International Organization for Plant Information. Books by Johann Friedrich Gmelin at Internet Archive Zoologica Göttingen State and University Library
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
Neolamprologus pulcher is a species of cichlid endemic to Lake Tanganyika where it prefers locations with plenty of sedimentation. The common name for N. pulcher is the daffodil cichlid. This species can reach a length of 10 centimetres TL, it can be found in the aquarium trade. It was believed that N. pulcher and N. brichardi were two distinct species. Now they are considered the same species, the only difference being that Neolamprologus brichardi has a black stripe running from its eye to its gill cover and a yellow spot just above it, both of which are absent in N. pulcher. Because Neolamprologus pulcher is the older of the two scientific names, the rules of scientific nomenclature would make this the correct name for the species; the daffodil cichlid, when it was still known as N. brichardi, was named after Pierre Brichard, a Belgian who set up a collection station, for the export of Tanganyikan cichlids in 1971, named "Fishes of Burundi." Daffodil cichlids are endemic to Lake Tanganyika and are widespread in the southern part of the lake.
They are found along the rocky coastlines of the countries of Burundi, the Democratic Republic of the Congo and Zambia. There are number of different geographical varieties; the variety known as the "daffodil" is popular and is found along the steep rocky slopes of Kantalamba and Kambwinba. Like other Lamprologini cichlids, daffodil cichlids are variable and are found in all kinds of habitats, they are found both at the surface and in deep waters, but all species are substrate spawners. They have a body that can be somewhat elongated to elongated, their colors tend to be brown, blue, black or a combination or all four. Black is a striping, either vertical or horizontal. Like other genus in the tribe, N. pulcher will mate with females of other Lamprologini. Daffodil cichlids inhabit rocky coastlines and swim in large schools that consist of hundreds of fish; when breeding however, they will spawn in caves. They are found in waters at depths of deeper, they feed on swarms of plankton drifting in the lake water along with microorganisms such as small crustaceans and invertebrates.
Daffodil cichlids are graceful fish with bodies. The tail fin is lyre shaped and they develop long flowing filaments on all unpaired fins, they reach up to about 4 - 5 inches in length, but can sometimes get a bit bigger in the aquarium reaching up to 6 inches. They can live 8 – 10 years with proper care; these fish have a light colored tan body washed with hints of bluish purple spots. The yellow is stronger along the upper portion of the body and onto the dorsal fin, around the base of the pectoral fin. There are two vertical crescent shaped bars just behind the eye highlighted with a bit of blue; the dorsal fin is lyre shaped and they develop long flowing filaments on all unpaired fins. The fins are tipped with an icy blue, they have brilliant blue eyes. Daffodil cichlids are omnivorous and feed on swarms of plankton in the water column as well as small crustaceans and invertebrates; the daffodil cichlid inhabits permanent social groups composed of one breeding pair and helpers of both sexes. Absolute breeding success has been shown to be higher for breeding pairs with helpers compared to those without helpers.
Egg size tends to decrease as the number of helpers within groups increases, which suggests that the presence of helpers enables breeder females to strategically reduce their investment per egg in a manner that maximizes breeder fitness. When parents and helpers care for offspring, the protection may reduce the predation risk to offspring, which may allow mothers to invest less per single offspring. Daffodil cichlid helpers reduce the offspring's mortality rate. Therefore, dominant females are expected to reduce their investment per egg when more helpers are present. Experiments show that females do indeed reduce egg size with increasing number of helpers but not when perceived neighbor density is high. In cooperatively breeding groups that have a mix of related and unrelated individuals, being able to identify and differentially cooperate with relatives can bring indirect fitness benefits to helpers; when given a choice between associating with unfamiliar kin or unfamiliar non-kin, juvenile daffodil cichlids spend longer time associating with kin.
Relatedness, rather than familiarity, is more important in the association preferences of the daffodil cichlid, advantageous because not all familiar individuals within a cooperatively breeding group are relatives. Having the ability to recognize kin from non-kin brings fitness advantages through kin selection and inbreeding avoidance. Kin selection can explain the evolution of cooperative breeding, the distribution of relatives within a population may influence the benefits of cooperative behavior. Females are more to inherit the breeding position of their mother or sister in larger groups. Helper to breeder relatedness decreases steeply with increasing helper age for breeding males. Helper to helper relatedness is age-associative and declines with age. Since daffodil cichlids are a species that uses cooperative breeding, this means that each individual is ranked in terms of social status. Breeders have a higher social rank than non-breeders. Social status has significant effects on daffodil cichlid behavior.
Within a group of breeding and helper cichlids, there exists a dominance hierarchy among every fish in the group. The breeder males and females are dominant individuals who have offspring, while the helper cichlids are su
The Serengeti ecosystem is a geographical region in Africa. It is located in northern Tanzania, it spans 30,000 km2. The Serengeti hosts the second largest terrestrial mammal migration in the world, which helps secure it as one of the Seven Natural Wonders of Africa, as one of the ten natural travel wonders of the world; the Serengeti is renowned for its large lion population and is one of the best places to observe prides in their natural environment. The region contains the Serengeti National Park in several game reserves. 70 large mammal and 500 bird species are found there. This high diversity is a function of diverse habitats, including riverine forests, kopjes and woodlands. Blue wildebeests, gazelles and buffalos are some of the found large mammals in the region. There has been controversy about a proposed road to be built through the Serengeti. Serengeti is derived from Maa. Much of the Serengeti was known to outsiders as Maasailand; the Maasai are known as fierce warriors and live alongside most wild animals with an aversion to eating game and birds, subsisting on their cattle.
Their strength and reputation kept the newly arrived Europeans from exploiting the animals and resources of most of their land. A rinderpest epidemic and drought during the 1890s reduced the numbers of both Maasai and animal populations; the Tanzanian government in the 20th century re-settled the Maasai around the Ngorongoro Crater. Poaching and the absence of fires, the result of human activity, set the stage for the development of dense woodlands and thickets over the next 30–50 years. Tsetse fly populations now prevented any significant human settlement in the area. By the mid-1970s, wildebeest and the Cape buffalo populations had recovered and were cropping the grass, reducing the amount of fuel available for fires; the reduced intensity of fires has allowed acacia to once again become established. In the 21st century, mass rabies vaccination programmes for domestic dogs in the Serengeti have not only indirectly prevented hundreds of human deaths, but protected wildlife species such as the endangered African wild dog.
Each year around the same time, the circular great wildebeest migration begins in the Ngorongoro Conservation Area of the southern Serengeti in Tanzania and loops in a clockwise direction through the Serengeti National Park and north towards the Masai Mara reserve in Kenya. This migration is a natural phenomenon determined by the availability of grazing; the initial phase lasts from January to March, when the calving season begins – a time when there is plenty of rain-ripened grass available for the 260,000 zebra that precede 1.7 million wildebeest and the following hundreds of thousands of other plains game, including around 470,000 gazelles. During February, the wildebeest spend their time on the short grass plains of the southeastern part of the ecosystem and giving birth to 500,000 calves within a 2 to 3-week period. Few calves are born ahead of time and of these, hardly any survive; the main reason is that young calves are more noticeable to predators when mixed with older calves from the previous year.
As the rains end in May, the animals start moving northwest into the areas around the Grumeti River, where they remain until late June. The crossings of the Grumeti and Mara rivers beginning in July are a popular safari attraction because crocodiles are lying in wait; the herds arrive in Kenya in late July / August, where they stay for the remainder of the dry season, except that the Thomson's and Grant's gazelles move only east/west. In early November, with the start of the short rains the migration starts moving south again, to the short grass plains of the southeast arriving in December in plenty of time for calving in February. About 250,000 wildebeest die during the journey from Tanzania to the Maasai Mara National Reserve in southwestern Kenya, a total of 800 kilometres. Death is from thirst, exhaustion, or predation; the Serengeti has some of East Africa's finest game areas. Besides being known for the great migration, the Serengeti is famous for its abundant large predators; the ecosystem is home to over 3,000 lions, 1,000 leopards, 7,700 to 8,700 spotted hyenas..
The East African cheetah are present in Serengeti. Wild dogs are scarce in much of the Serengeti; this is true in places such as Serengeti National Park, in which lions and spotted hyenas, predators that steal wild dog kills and are a direct cause of wild dog mortality, are abundant. The Serengeti is home to a diversity of grazers, including African buffalo, Grant's gazelle, eland and topi; the Serengeti can support this remarkable variety of grazers only because each species those that are related, has a different diet. For example, wildebeests prefer to consume shorter grasses. Dik-diks eat the lowest leaves of a tree, impalas eat the leaves that are higher up, giraffes eat leaves that are higher; the governments of Tanzania and Kenya maintain a number of protected areas, including national parks, conservation areas, game reserves, that give legal protection to over 80 percent of the Serengeti. The southeastern area lies in the rain shadow of the Ngorongoro Conservation Area's highlands and is composed of shortgrass treeless plains with abundant small dicots.
Soils are high in nutrients, overlying a shallow calcareous hardpan due to natrocarbonatite eruptions from Ol Do
A frog is any member of a diverse and carnivorous group of short-bodied, tailless amphibians composing the order Anura. The oldest fossil "proto-frog" appeared in the early Triassic of Madagascar, but molecular clock dating suggests their origins may extend further back to the Permian, 265 million years ago. Frogs are distributed, ranging from the tropics to subarctic regions, but the greatest concentration of species diversity is in tropical rainforests. There are accounting for over 85 % of extant amphibian species, they are one of the five most diverse vertebrate orders. Warty frog species tend to be called toads, but the distinction between frogs and toads is informal, not from taxonomy or evolutionary history. An adult frog has a stout body, protruding eyes, anteriorly-attached tongue, limbs folded underneath, no tail. Frogs have glandular skin, with secretions ranging from distasteful to toxic, their skin varies in colour from well-camouflaged dappled brown and green to vivid patterns of bright red or yellow and black to show toxicity and ward off predators.
Adult frogs live on dry land. Frogs lay their eggs in water; the eggs hatch into aquatic larvae called tadpoles that have internal gills. They have specialized rasping mouth parts suitable for herbivorous, omnivorous or planktivorous diets; the life cycle is completed. A few species bypass the tadpole stage. Adult frogs have a carnivorous diet consisting of small invertebrates, but omnivorous species exist and a few feed on fruit. Frog skin has a rich microbiome, important to their health. Frogs are efficient at converting what they eat into body mass, they are an important food source for predators and part of the food web dynamics of many of the world's ecosystems. The skin is semi-permeable, making them susceptible to dehydration, so they either live in moist places or have special adaptations to deal with dry habitats. Frogs produce a wide range of vocalizations in their breeding season, exhibit many different kinds of complex behaviours to attract mates, to fend off predators and to survive.
Frogs are valued as food by humans and have many cultural roles in literature and religion. Frog populations have declined since the 1950s. More than one third of species are considered to be threatened with extinction and over 120 are believed to have become extinct since the 1980s; the number of malformations among frogs is on the rise and an emerging fungal disease, has spread around the world. Conservation biologists are working to resolve them; the use of the common names "frog" and "toad" has no taxonomic justification. From a classification perspective, all members of the order Anura are frogs, but only members of the family Bufonidae are considered "true toads"; the use of the term "frog" in common names refers to species that are aquatic or semi-aquatic and have smooth, moist skins. There are numerous exceptions to this rule; the European fire-bellied toad has a warty skin and prefers a watery habitat whereas the Panamanian golden frog is in the toad family Bufonidae and has a smooth skin.
The origin of the order name Anura — and its original spelling Anoures — is the Ancient Greek "alpha privative" prefix ἀν- "without", οὐρά, meaning "animal tail". It refers to the tailless character of these amphibians; the origins of the word frog are debated. The word is first attested in Old English as frogga, but the usual Old English word for the frog was frosc, it is agreed that the word frog is somehow related to this. Old English frosc remained in dialectal use in English as frosh and frosk into the nineteenth century, is paralleled in other Germanic languages, with examples in the modern languages including German Frosch, Icelandic froskur, Dutch vors; these words allow us to reconstruct a Common Germanic ancestor *froskaz. The third edition of the Oxford English Dictionary finds that the etymology of *froskaz is uncertain, but agrees with arguments that it could plausibly derive from a Proto-Indo-European base along the lines of *preu = "jump". How Old English frosc gave rise to frogga is, uncertain, as the development does not involve a regular sound-change.
Instead, it seems that there was a trend in Old English to coin nicknames for animals ending in -g, with examples—themselves all of uncertain etymology—including dog, pig and wig. Frog appears to have been adapted from frosc as part of this trend. Meanwhile, the word toad, first attested as Old English tādige, is unique to English and is of uncertain etymology, it is the basis for the word tadpole, first attested as Middle English taddepol meaning'toad-head'. About 88% of amphibian species are classified in the order Anura; these include over 7,000 species in 56 families, of which the Craugastoridae, Hylidae and Bufonidae are the richest in species. The Anura include any fossil species that fit within the anuran definition; the characteristics of anuran adults include: 9 or fewer presacral vertebrae, the presence of a urostyle formed of fused vertebrae, no tail, a long and forward-sloping ilium, shorter fore limbs than hind limbs and ulna fused and fibula fused, elongated an
Millipedes are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments. Each double-legged segment is a result of two single segments fused together. Most millipedes have elongated cylindrical or flattened bodies with more than 20 segments, while pill millipedes are shorter and can roll into a ball. Although the name "millipede" derives from the Latin for "thousand feet", no known species has 1,000. There are 12,000 named species classified into 16 orders and around 140 families, making Diplopoda the largest class of myriapods, an arthropod group which includes centipedes and other multi-legged creatures. Most millipedes are eating decaying leaves and other dead plant matter; some eat fungi or suck plant fluids, a small minority are predatory. Millipedes are harmless to humans, although some can become household or garden pests. Millipedes can be unwanted in greenhouses where they can cause severe damage to emergent seedlings. Most millipedes defend themselves with a variety of chemicals secreted from pores along the body, although the tiny bristle millipedes are covered with tufts of detachable bristles.
Reproduction in most species is carried out by modified male legs called gonopods, which transfer packets of sperm to females. First appearing in the Silurian period, millipedes are some of the oldest known land animals; some members of prehistoric groups grew to over 2 m. The longest extant species is the giant African millipede. Among myriapods, millipedes have traditionally been considered most related to the tiny pauropods, although some molecular studies challenge this relationship. Millipedes can be distinguished from the somewhat similar but only distantly related centipedes, which move are carnivorous, have only a single pair of legs on each body segment; the scientific study of millipedes is known as diplopodology, a scientist who studies them is called a diplopodologist. The scientific name "Diplopoda" comes from the Ancient Greek words διπλοῦς, "double" and ποδός, "foot", referring to the appearance of two pairs of legs on most segments, as described below; the common name "millipede" is a compound word formed from the Latin roots ped.
The term "millipede" is widespread in popular and scientific literature, but among North American scientists, the term "milliped" is used. Other vernacular names include "thousand-legger" or "diplopod"; the science of millipede biology and taxonomy is called diplopodology: the study of diplopods. 12,000 millipede species have been described. Estimates of the true number of species on earth range from 15,000 to as high as 80,000. Few species of millipede are at all widespread; these factors have favoured genetic isolation and rapid speciation, producing many lineages with restricted ranges. The living members of the Diplopoda are divided into sixteen orders in two subclasses; the basal subclass Penicillata contains Polyxenida. All other millipedes belong to the subclass Chilognatha consisting of two infraclasses: Pentazonia, containing the short-bodied pill millipedes, Helminthomorpha, containing the great majority of the species; the higher-level classification of millipedes is presented below, based on Shear, 2011, Shear & Edgecombe, 2010.
Recent cladistic and molecular studies have challenged the traditional classification schemes above, in particular the position of the orders Siphoniulida and Polyzoniida is not yet well established. The placement and positions of extinct groups known only from fossils is tentative and not resolved. After each name is listed the author citation: the name of the person who coined the name or defined the group if not at the current rank. Class Diplopoda de Blainville in Gervais, 1844 Subclass Penicillata Latrielle, 1831 Order Polyxenida Verhoeff, 1934 Subclass †Arthropleuridea Order †Arthropleurida Waterlot, 1934 Order †Eoarthropleurida Shear & Selden, 1995 Order †Microdecemplicida Wilson & Shear, 2000 Subclass Chilognatha Latrielle, 1802 Order †Zosterogrammida Wilson, 2005 Infraclass Pentazonia Brandt, 1833 Order †Amynilyspedida Hoffman, 1969 Superorder Limacomorpha Pocock, 1894 Order Glomeridesmida Cook, 1895 Superorder Oniscomorpha Pocock, 1887 Order Glomerida Brandt, 1833 Order Sphaerotheriida Brandt, 1833 Infraclass Helminthomorpha Pocock, 1887 Superorder †Archipolypoda Scudder, 1882 Order †Archidesmida Wilson & Anderson 2004 Order †Cowiedesmida Wilson & Anderson 2004 Order †Euphoberiida Hoffman, 1969 Order †Palaeosomatida Hannibal & Krzeminski, 2005 Order †Pleurojulida Schneider & Werneburg, 1998 Subterclass Colobognatha Brandt, 1834 Order Platydesmida Cook, 1895 Order Polyzoniida Cook, 1895 Order Siphonocryptida Cook, 1895 Order Siphonophorida Newport, 1844 Subterclass Eugnatha Attems, 1898 Superorder Juliformia Attems, 1926 Order Julida Brandt, 1833 Order Spirobolida Cook, 1895 Order Spirostreptida Brandt, 1833 Superfamily †Xyloiuloidea Cook, 1895 Superorder Nematophora Verhoeff, 1913 Order Callipodida Pocock, 1894 Order Chordeumatida Pocock 1894 Order Stemmiulida Cook, 1895 Order Siphoniulida Cook, 1895 Superorder Merocheta C
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