A holotype is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several examples, but explicitly designated as the holotype. Under the International Code of Zoological Nomenclature (ICZN), a holotype is one of several kinds of name-bearing types. In the International Code of Nomenclature for algae, fungi, and plants (ICN) and ICZN, the definitions of types are similar in intent but not identical in terminology or underlying concept.
For example, the holotype for the butterfly Plebejus idas longinus is a preserved specimen of that subspecies, held by the Museum of Comparative Zoology at Harvard University. In botany, an isotype is a duplicate of the holotype, where holotype and isotypes are often pieces from the same individual plant or samples from the same gathering.
A holotype is not necessarily "typical" of that taxon, although ideally it is. Sometimes just a fragment of an organism is the holotype, particularly in the case of a fossil. For example, the holotype of Pelorosaurus humerocristatus (Duriatitan), a large herbivorous dinosaur from the early Jurassic period, is a fossil leg bone stored at the Natural History Museum in London. Even if a better specimen is subsequently found, the holotype is not superseded.
Under the ICN, an additional and clarifying type could be designated an epitype under article 9.8, where the original material is demonstrably ambiguous or insufficient.
A conserved type (ICN article 14.3) is sometimes used to correct a problem with a name which has been misapplied; this specimen replaces the original holotype.
In the absence of a holotype, another type may be selected, out of a range of different kinds of type, depending on the case, a lectotype or a neotype.
For example, in both the ICN and the ICZN a neotype is a type that was later appointed in the absence of the original holotype.
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thumb|Holotype de l'étoile de mer fossile Marocaster, au Muséum de Toulouse. thumb|Holotype de la rascasse fossile Scorpaena jeanneli, au Muséum de Paris. thumb|220px|Holotype de Lethe corbieri, papillon fossile de l'Oligocène de Provence. thumb|Holotype de Testudo hermanni Gmelin, 1789 (plastron détaché), Musée zoologique de Strasbourg En systématique, un type est l'élément de référence attaché à un nom scientifique à partir duquel une espèce a été décrite.
vignette| redresse=1.2| L'espèce est l'unité de base de la classification du vivant. Dans les sciences du vivant, l’espèce (du latin species, « type » ou « apparence ») est le taxon de base de la systématique. La définition la plus communément admise est celle du concept biologique : une espèce est un ensemble d'individus qui peuvent effectivement ou potentiellement se reproduire entre eux et engendrer une descendance viable et féconde, dans des conditions naturelles.
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Delamination propagation in fibrous laminates is often accompanied by development of a damage zone, within which intact fibers bridge the crack faces that constitutes a major toughening mechanism. A direct experimental assessment of the crack closure tract ...
EPFL2016
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Fiber reinforced composites can develop large scale bridging upon mode I fracture. This toughening mechanism depends on the constituents and the geometry of the specimen, and is especially important in unidirectional laminates when fracture is parallel to ...
It was recently proposed that Fornasinius insignis ab. funereus Burgeon, 1937 be raised from the synonymy with Fornasinius fornasini Bertoloni, 1853 and recognized as a good species (Tauzin, 2017). Regrettably, this proposition was based on the misidentifi ...