Macropterygius Temporal range: Late Jurassic, | |
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Scientific classification | |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Order: | † Ichthyosauria |
Family: | † Ophthalmosauridae |
Genus: | † Macropterygius Huene, 1922 ( nomen conservandum ) |
Species: | †M. trigonus |
Binomial name | |
†Macropterygius trigonus (Owen, 1840) (nomen conservandum) | |
Synonyms | |
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Macropterygius is a genus of ichthyosaurs known from the Late Jurassic (Kimmeridgian age) of England (Kimmeridge Clay formation). Though many specimens have been referred to this genus from all over Europe, the type specimen of the only recognized species, M. trigonus, consists of just a single vertebra. Because this cannot be used to distinguish ichthyosaurs from one another, the genus and species are currently considered nomina dubia (doubtful names). [2]
Originally described by Owen (1840) as a species of the genus Ichthyosaurus (I. trigonus). It has had an unstable taxonomic history, partly because the species was originally named without designating any particular specimen as the holotype. In 1889, the original type specimen of I. trigonus used by richard Owen was thought to be lost, and so Lydekker named several isolated vertebrae as the "type" of this species, though during this time there was no formal concept of a neotype. This created a problem, because the vertebrae selected by Lydekker came from unknown sediments and were not definitely associated with the original specimens named and described by Owen. Matters were complicated when the original holotype used by Owen was re-discovered, making the designation of a neotype unnecessary. This situation was not officially fixed until 1993, when the International Commission on Zoological Nomenclature formally declared that Lydekker's statement about the "type" did not count as designating a neotype, and so the designation did not need to be reversed in light of the holotype's re-discovery. The ICZN, in the same decision (Opinion 1734, Case 2779), added the genus Macropterygius and species M. trigonus (originally I. trigonus) to the list of generic and specific names, making both names nomina conservanda . The original holotype specimen is currently held by the Academy of Natural Sciences in Philadelphia, cataloged as specimen number ANSP 10124. [3]
In 2000, Bardet and Fernández found that the holotype specimen of Macropterygius trigonus is undiagnosible beyond the level of Ophthalmosauridae, thus this genus and species were considered nomina dubia . [2]
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example 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.
In biology, a type is a particular specimen of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the defining features of that particular taxon. In older usage, a type was a taxon rather than a specimen.
In binomial nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application.
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This is a list of terms and symbols used in scientific names for organisms, and in describing the names. For proper parts of the names themselves, see List of Latin and Greek words commonly used in systematic names. Note that many of the abbreviations are used with or without a stop.
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