''Macropterygius'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

ichthyosaur Ichthyosaurs (Ancient Greek for "fish lizard" – and ) are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia ('fish flippers' – a designation introduced by Sir Richard Owen in 1842, altho ...

s known from the

Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the ...

(

Kimmeridgian In the geologic timescale, the Kimmeridgian is an age in the Late Jurassic Epoch and a stage in the Upper Jurassic Series. It spans the time between 157.3 ± 1.0 Ma and 152.1 ± 0.9 Ma (million years ago). The Kimmeridgian follows the Oxford ...

age) of

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

(

Kimmeridge Clay The Kimmeridge Clay is a sedimentary deposit of fossiliferous marine clay which is of Late Jurassic to lowermost Cretaceous age and occurs in southern and eastern England and in the North Sea. This rock formation is the major source rock for Nor ...

formation). Though many specimens have been referred to this genus from all over Europe, the

type specimen In biology, a type is a particular specimen (or in some cases a group of specimens) 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 ...

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).

Discovery and species

Originally described by Owen (1840) as a species of the genus ''

Ichthyosaurus ''Ichthyosaurus'' (derived from Greek ' () meaning 'fish' and ' () meaning 'lizard') is a genus of ichthyosaurs from the Early Jurassic (Hettangian - Pliensbachian), with possible Late Triassic record, from Europe (Belgium, England, Germany, Sw ...

'' (''I. trigonus''). It has had an unstable taxonomic history, partly because the species was originally named without designating any particular specimen as the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

. 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 In biology, a type is a particular specimen (or in some cases a group of specimens) 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 th ...

. 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 The International Commission on Zoological Nomenclature (ICZN) is an organization dedicated to "achieving stability and sense in the scientific naming of animals". Founded in 1895, it currently comprises 26 commissioners from 20 countries. Orga ...

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 The Academy of Natural Sciences of Drexel University, formerly the Academy of Natural Sciences of Philadelphia, is the oldest natural science research institution and museum in the Americas. It was founded in 1812, by many of the leading natu ...

in Philadelphia, cataloged as specimen number ANSP 10124.ICZN (1993). "Opinion 1734: ''Ichthyosaurus trigonus'' Owen, 1840 (currently ''Macropterygius trigonus''; Reptilia, Ichthyopterygia): neotype replaced by rediscovered holotype." ''Bulletin of Zoological Nomenclature'', 50: 184-18

/ref> In 2000, Bardet and Fernández found that the holotype specimen of ''Macropterygius trigonus'' is undiagnosible beyond the level of

Ophthalmosauridae Ophthalmosauridae is an extinct family of thunnosaur ichthyosaurs from the Middle Jurassic to the early Late Cretaceous (Bajocian - Cenomanian) worldwide. Almost all ichthyosaurs from the Middle Jurassic onwards belong to the family, until the e ...

, thus this genus and species were considered ''

nomina dubia In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a s ...

''.Bardet N, Fernández M. 2000. A new ichthyosaur from the Upper Jurassic lithographic limestones of Bavaria.''Journal of Paleontology'' 74 (3): 503-511.

References

Fossil taxa described in 1840 Ichthyosaurs of Europe Late Jurassic ichthyosaurs Solnhofen fauna Ichthyosauromorph genera {{jurassic-reptile-stub

Discovery and species

See also

References