In biology , a taxon ( back-formation from taxonomy ; pl. : taxa ) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and given a particular ranking , especially if and when it is accepted or becomes established. It is very common, however, for taxonomists to remain at odds over what belongs to a taxon and the criteria used for inclusion, especially in the context of rank-based (" Linnaean ") nomenclature (much less so under phylogenetic nomenclature ). If a taxon is given a formal scientific name , its use is then governed by one of the nomenclature codes specifying which scientific name is correct for a particular grouping.
31-513: Acanthomorpha (meaning "thorn-shaped") is an extraordinarily diverse taxon of teleost fishes with spiny fin rays . The clade contains about one-third of the world's modern species of vertebrates: over 14,000 species. A key anatomical innovation in acanthomorphs is hollow and unsegmented spines at the anterior edge of the dorsal and anal fins. A fish can extend these sharp bony spines to protect itself from predators, but can also retract them to decrease drag when swimming. Another shared feature
62-416: A catalogue of the plants that are on show in the royal garden of Montpellier] 1720 , Novus caracter [sic] plantarum, in duo tractatus divisus: primus, de herbis & subfructibus, secundus, de fructibus & arboribus. Montpellier, posthumous edition, attended to by his son, Antoine Magnol (1676–1759). [New character of plants, divided into two treatises: the first on herbs and small shrublike plants,
93-635: A list of the plants growing around Montpellier, with descriptions and plates of several plants added. With an appendix that contains plants newly found and corrects previous errors] 1689 , Prodromus historiae generalis plantarum, in quo familiae plantarum per tabulas disponuntur. Montpellier. [Precursor to a general history of plants, in which the families of plants are arranged in tables] 1697 , Hortus regius Monspeliense, sive Catalogus plantarum quae in Horto Regio Monspeliensi demonstrantur. Montpellier. [The royal garden of Montpellier, or rather
124-440: A natural classification of groups of plants that have features in common. Pierre Magnol was born into a family of apothecaries (pharmacists). His father Claude ran a pharmacy as did his grandfather Jean Magnol. Pierre's mother was from a family of physicians. Pierre's older brother Cesar succeeded his father in the pharmacy. Pierre, being one of the younger children, had more freedom to choose his own profession, and wanted to become
155-514: A physician. He had become devoted to natural history and especially botany at an early stage in his life. He enrolled as a student in medicine at the University of Montpellier on 19 May 1655. By Magnol's time the city of Montpellier was already long established as an important commercial and educational centre. The University of Montpellier was the first French university to establish a botanic garden, donated in 1593 by King Henry IV of France for
186-470: Is a particular rostral cartilage, associated with ligaments attached to the rostrum and premaxilla, that enables the fish to protrude its jaws considerably to catch food. Rosen coined the name in 1973 to describe a clade comprising Acanthopterygii, Paracanthopterygii, and also ctenothrissiform fossils from the Cretaceous period, such as Aulolepis and Ctenothrissa . Those fossils share several details of
217-545: Is included in the Reptilia (birds are traditionally placed in the class Aves , and mammals in the class Mammalia ). The term taxon was first used in 1926 by Adolf Meyer-Abich for animal groups, as a back-formation from the word taxonomy ; the word taxonomy had been coined a century before from the Greek components τάξις ( táxis ), meaning "arrangement", and νόμος ( nómos ), meaning " method ". For plants, it
248-500: Is relative, and restricted to a particular systematic schema. For example, liverworts have been grouped, in various systems of classification, as a family, order, class, or division (phylum). The use of a narrow set of ranks is challenged by users of cladistics ; for example, the mere 10 ranks traditionally used between animal families (governed by the International Code of Zoological Nomenclature (ICZN)) and animal phyla (usually
279-533: Is without doubt the invention of the concept of plant families, a natural classification, based on combinations of morphological characters, as set out in his Prodromus historiae generalis plantarum, in quo familiae plantarum per tabulas disponuntur (1689) (See under major works ). His work may be regarded as one of the first steps towards the composition of a tree of life. In his Prodromus he developed 76 tables, which not only grouped plants into families but also allowed for an easy and rapid identification by means of
310-530: The Edict of Nantes (1598), Protestants officially had religious freedom and the right to work in any field or for the state. The edict did not end religious persecution and discrimination. In his life, Magnol was several times denied a position because of religious discrimination. With the revocation of the Edict of Nantes in 1685, Magnol renounced Protestantism and converted to Catholicism. In December 1663 Magnol received
341-668: The Languedoc , the Provence , to the Alps and to the Pyrenees . In 1664 there was a vacancy for 'Demonstrator of plants' in Montpellier and Magnol was proposed for the position. He was denied the appointment because of religious discrimination. This happened again in 1667 when he was the leading candidate for the chair of Professor of medicine. Meanwhile Magnol had contacts with many prominent botanist and
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#1733092852835372-463: The clade , is equivalent to the taxon, assuming that taxa should reflect evolutionary relationships. Similarly, among those contemporary taxonomists working with the traditional Linnean (binomial) nomenclature, few propose taxa they know to be paraphyletic . An example of a long-established taxon that is not also a clade is the class Reptilia , the reptiles; birds and mammals are the descendants of animals traditionally classed as reptiles, but neither
403-1413: The early part of the Late Cretaceous from the Cenomanian to the Campanian , but become exceedingly rare throughout the Maastrichtian and the Paleocene (spanning the likely origins of a number of modern taxa) before a second explosion in fossil abundance and diversity in the Eocene . This mysterious gap is known as "Patterson's Gap" after paleontologist Colin Patterson , who first identified it in 1993. The phylogeny of living bony fishes Lampridiformes ( oarfish , opah , ribbonfish ) [REDACTED] Percopsiformes (troutperches) [REDACTED] Zeiformes (dories) [REDACTED] Stylephoriformes (tube-eyes, thread-fins) Gadiformes (cods) [REDACTED] Polymixiiformes (beardfish) [REDACTED] Beryciformes (alfonsinos; whalefishes) [REDACTED] Trachichthyiformes (pinecone fishes; slimeheads) [REDACTED] Holocentriformes (squirrelfish; soldier fishes) [REDACTED] Percomorpha [REDACTED] Some otoliths , calcium carbonate structures that form
434-595: The ears of fishes, have been found from the Jurassic Period that may belong to acanthomorphs, but the oldest body fossils from this taxon are only known from the middle of the Cretaceous Period, about 100 million years ago. Acanthomorphs from the early Late Cretaceous were small, typically about 4 centimeters long, and fairly rare. Toward the beginning of the Cenozoic era, they exploded in an adaptive radiation, so by
465-476: The fairly sophisticated folk taxonomies. Much later, Aristotle, and later still, European scientists, like Magnol , Tournefort and Carl Linnaeus 's system in Systema Naturae , 10th edition (1758), , as well as an unpublished work by Bernard and Antoine Laurent de Jussieu , contributed to this field. The idea of a unit-based system of biological classification was first made widely available in 1805 in
496-567: The founding members of the Société Royale des Sciences de Montpellier (1706) and held one of the three chairs in botany. In 1709 he was called to Paris to occupy the seat in the Académie Royale des Sciences de Paris that was left empty when his former student Joseph Pitton de Tournefort died prematurely. Among Magnol's students were Tournefort and the brothers Antoine and Bernard de Jussieu . Magnol's most important contribution to science
527-466: The highest relevant rank in taxonomic work) often cannot adequately represent the evolutionary history as more about a lineage's phylogeny becomes known. In addition, the class rank is quite often not an evolutionary but a phenetic or paraphyletic group and as opposed to those ranks governed by the ICZN (family-level, genus-level and species -level taxa), can usually not be made monophyletic by exchanging
558-405: The honorary title brevet de médecine royal through mediation of Antoine Vallot , an influential physician of the king. No means of his financial stability are mentioned (Magnol did not have a wealthy family to support him) but it is suggested that he was practicing medicine and had an income out of that. From 1659 on he devoted much of his time to the study of botany and made several trips through
589-682: The introduction of Jean-Baptiste Lamarck 's Flore françoise , and Augustin Pyramus de Candolle 's Principes élémentaires de botanique . Lamarck set out a system for the "natural classification" of plants. Since then, systematists continue to construct accurate classifications encompassing the diversity of life; today, a "good" or "useful" taxon is commonly taken to be one that reflects evolutionary relationships . Many modern systematists, such as advocates of phylogenetic nomenclature , use cladistic methods that require taxa to be monophyletic (all descendants of some ancestor). Therefore, their basic unit,
620-516: The morphological characters, the same he used to compose the groups (Magnol, 1689). 1676 , Botanicum Monspeliense, sive Plantarum circa Monspelium nascentium index. Lyon. [Flora of Montpellier, or rather a list of the plants growing around Montpellier] 1686 , Botanicum Monspeliense, sive Plantarum circa Monspelium nascentium index. Adduntur variarum plantarum descriptiones et icones. Cum appendice quae plantas de novo repertas continet et errata emendat. Montpellier. [Flora of Montpellier, or rather
651-429: The second on shrubs and trees] In 1703 Charles Plumier (1646–1704) named a flowering tree from the island of Martinique Magnolia , after Magnol. The name was later adopted by William Sherard , when he did the nomenclatural parts of Hortus Elthamensis by Johann Jacob Dillenius , and The Natural History of Carolina by Mark Catesby , to denote a flowering tree now known as Magnolia virginiana , taking it for
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#1733092852835682-565: The skeleton, and especially of the skull, with modern acanthomorphs. Originally based on anatomy, Acanthomorpha has been borne out by more recent molecular analyses. The oldest acanthomorphs were initially reported by Louis Agassiz from the Cenomanian Sannine Formation of Lebanon, and were considered as such for over a century until slightly older remains were identified from the end- Albian of Mexico . Early acanthomorph fossils are diverse and well-preserved in formations from
713-405: The study of medicine and pharmacology. Its medical school attracted students from all over Europe. Individuals well-known in medicine and botany such as Leonhart Fuchs (1501–1566), Guillaume Rondelet (1507–1566), Charles de l'Ecluse (1526–1609), Pierre Richer de Belleval (c. 1564–1632), and the great writer (and doctor) François Rabelais (c. 1493–1553), all studied at this university. So it
744-544: The taxa contained therein. This has given rise to phylogenetic taxonomy and the ongoing development of the PhyloCode , which has been proposed as a new alternative to replace Linnean classification and govern the application of names to clades . Many cladists do not see any need to depart from traditional nomenclature as governed by the ICZN, International Code of Nomenclature for algae, fungi, and plants , etc. Pierre Magnol Pierre Magnol (8 June 1638 – 21 May 1715)
775-556: The time their fossils begin appear more frequently in Eocene-aged strata, they had reached their modern diversity of 300 families. Recently discovered fish scales from Poland suggest that the oldest acanthomorphs occurred in the Late Triassic. Notes Sources Taxon Initial attempts at classifying and ordering organisms (plants and animals) were presumably set forth in prehistoric times by hunter-gatherers, as suggested by
806-516: Was a French botanist . He was born in the city of Montpellier , where he lived and worked for most of his life. He became Professor of Botany and Director of the Royal Botanic Garden of Montpellier and held a seat in the Académie Royale des Sciences de Paris for a short while. He was one of the innovators who devised the botanical scheme of classification. He was the first to publish the concept of plant families as they are understood today,
837-420: Was always used for animals, whereas "division" was traditionally often used for plants , fungi , etc. A prefix is used to indicate a ranking of lesser importance. The prefix super- indicates a rank above, the prefix sub- indicates a rank below. In zoology , the prefix infra- indicates a rank below sub- . For instance, among the additional ranks of class are superclass, subclass and infraclass. Rank
868-556: Was highly esteemed by his contemporaries. He corresponded with John Ray , William Sherard and James Petiver (England), Paul Hermann and Petrus Houttuyn ( Leiden ), Jan Commelin (Amsterdam), J.H. Lavater ( Zürich ) and J. Salvador ( Barcelona ), among others. In 1687, after his conversion to Catholicism, Magnol eventually became 'Demonstrator of plants' at the botanic garden of Montpellier. In 1693, recommended by Guy-Crescent Fagon (1638–1718), then court physician, and his own student Joseph Pitton de Tournefort (1656–1708), he
899-420: Was in one of the intellectual and botanical capitals that Magnol took his education. He got his doctor's degree (M.D.) on 11 January 1659. After receiving his degree, his attention once again shifted to botany, this time even more seriously. Montpellier was a bastion of Protestantism and Magnol was raised in the tradition of Calvinism . At that time, Roman Catholicism was the official state church, but since
930-457: Was nominated 'doctor to the kings court'. In 1694 he finally was appointed Professor of medicine at the University of Montpellier. Through intervention of Fagon, he received a brevet de professeur royale . Magnol was also appointed Director of the botanic garden in 1696, for a three-year period. After that, he received the title 'Inspector of the garden' for the rest of his life. Magnol was one of
961-543: Was proposed by Herman Johannes Lam in 1948, and it was adopted at the VII International Botanical Congress , held in 1950. The glossary of the International Code of Zoological Nomenclature (1999) defines a A taxon can be assigned a taxonomic rank , usually (but not necessarily) when it is given a formal name. " Phylum " applies formally to any biological domain , but traditionally it