This list of xiphosurans is a comprehensive listing of all

genera 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 nomenclat ...

that have ever been included in the order

Xiphosura Xiphosura () is an order of arthropods related to arachnids. They are more commonly known as horseshoe crabs (a name applied more specifically to the only extant family, Horseshoe crab, Limulidae). They first appeared in the Hirnantian (Late Ordo ...

, excluding purely vernacular terms. The list includes all commonly accepted genera, but also genera that are now considered invalid, doubtful (''

nomen dubium 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 ...

''), or were not formally published (''

nomen nudum In taxonomy, a ''nomen nudum'' ('naked name'; plural ''nomina nuda'') is a designation which looks exactly like a scientific name of an organism, and may have originally been intended to be one, but it has not been published with an adequate descr ...

''), as well as

junior synonyms The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linn ...

of more established names, genera that are no longer considered xiphosurans and misspellings. The list currently includes 54 names out of which 31 are considered valid xiphosuran genera. As of 2019, there were around 80 extinct species of xiphosurans and 4 extant species of xiphosurans recognized as valid.

Naming conventions and terminology

There is no "official" or "canonical" list of xiphosuran genera. The closest thing is found contained in the regularly updated ''Summary list of fossil spiders and their relatives'' in the

World Spider Catalog The World Spider Catalog (WSC) is an online searchable database concerned with spider taxonomy. It aims to list all accepted families, genera and species, as well as provide access to the related taxonomic literature. The WSC began as a series of ...

, which include just the extinct species. The vast majority or all of the content of the list below, including the valid genera, preoccupied names, junior synonyms, misspellings, taxonomical classifications and sites of discovery, is based upon the 2019 edition of the summary list. Naming conventions and terminology follow the

International Code of Zoological Nomenclature The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its publisher, the ...

. Technical terms used include: *

Junior synonym The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linna ...

: A name which describes the same taxon as a previously published name. If two or more genera are formally designated and the

type specimens 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 t ...

are later assigned to the same genus, the first to be published (in chronological order) is the senior synonym, and all other instances are junior synonyms. Senior synonyms are generally used, except by special decision of the ICZN, but junior synonyms cannot be used again, even if deprecated. Junior synonymy is often subjective, unless the genera described were both based on the same type specimen. * ''

Nomen nudum In taxonomy, a ''nomen nudum'' ('naked name'; plural ''nomina nuda'') is a designation which looks exactly like a scientific name of an organism, and may have originally been intended to be one, but it has not been published with an adequate descr ...

'' (Latin for "naked name"): A name that has appeared in print but has not yet been formally published by the standards of the ICZN. ''Nomina nuda'' (the plural form) are invalid, and are therefore not italicized as a proper generic name would be. If the name is later formally published, that name is no longer a ''nomen nudum'' and will be italicized on this list. Often, the formally published name will differ from any ''nomina nuda'' that describe the same specimen. * ''

Nomen oblitum In zoological nomenclature, a ''nomen oblitum'' (plural: ''nomina oblita''; Latin for "forgotten name") is a disused scientific name which has been declared to be obsolete (figuratively 'forgotten') in favour of another 'protected' name. In its p ...

'' (Latin for "forgotten name"): A name that has not been used in the scientific community for more than fifty years after its original proposal. * Preoccupied name: A name that is formally published, but which has already been used for another taxon. This second use is invalid (as are all subsequent uses) and the name must be replaced. As preoccupied names are not valid generic names, they will also go unitalicized on this list. * ''

Nomen dubium 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 ...

'' (Latin for "dubious name"): A name describing a fossil with no unique diagnostic features.

Xiphosuran genera

† = Extinct

Xiphosuran ichnogenera

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Kouphichnium ''Kouphichnium'' is an ichnogenus that has been attributed to limulids (horseshoe crabs). ''Kouphichnium'' fossils resemble the footprints of birds, sometimes in conjunction with a medial line, and were initially thought to be bird or pterosaur ...

'' , Nopcsa , 1923 , Valid ,

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

, * * * * * * * , -

References

{{reflist Xiphosura Lists of prehistoric arthropods

Naming conventions and terminology

Xiphosuran genera

Xiphosuran ichnogenera

See also

References