Genus ( plural genera ) is a
taxonomic rank
In biological classification, taxonomic rank is the relative level of a group of organisms (a taxon) in an ancestral or hereditary hierarchy. A common system consists of species, genus, family (biology), family, order (biology), order, class (b ...
used in the
biological classification
In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are given ...
of
living
Living or The Living may refer to:
Common meanings
*Life, a condition that distinguishes organisms from inorganic objects and dead organisms
** Living species, one that is not extinct
*Personal life, the course of an individual human's life
* Hu ...
and
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
organism
In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
s as well as
virus
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsky's 1 ...
es.
In the hierarchy of biological classification, genus comes above
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
and below
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
. In
binomial nomenclature
In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...
, the genus name forms the first part of the binomial species name for each species within the genus.
:E.g. ''
Panthera leo
The lion (''Panthera leo'') is a large cat of the genus ''Panthera'' native to Africa and India. It has a muscular, broad-chested body; short, rounded head; round ears; and a hairy tuft at the end of its tail. It is sexually dimorphic; adult ...
'' (lion) and ''
Panthera onca
The jaguar (''Panthera onca'') is a large cat species and the only living member of the genus ''Panthera'' native to the Americas. With a body length of up to and a weight of up to , it is the largest cat species in the Americas and the thi ...
'' (jaguar) are two species within the genus ''
Panthera
''Panthera'' is a genus within the family (biology), family Felidae that was named and described by Lorenz Oken in 1816 who placed all the spotted cats in this group. Reginald Innes Pocock revised the classification of this genus in 1916 as co ...
''. ''Panthera'' is a genus within the family
Felidae
Felidae () is the family of mammals in the order Carnivora colloquially referred to as cats, and constitutes a clade. A member of this family is also called a felid (). The term "cat" refers both to felids in general and specifically to the ...
.
The composition of a genus is determined by
taxonomists
In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are given ...
. The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful:
#
monophyly
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...
– all descendants of an
ancestral
An ancestor, also known as a forefather, fore-elder or a forebear, is a parent or (recursively) the parent of an antecedent (i.e., a grandparent, great-grandparent, great-great-grandparent and so forth). ''Ancestor'' is "any person from whom ...
taxon
In biology, a taxon (back-formation from ''taxonomy''; plural 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 nam ...
are grouped together (i.e.
phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
analysis should clearly demonstrate both monophyly and validity as a separate lineage).
# reasonable compactness – a genus should not be expanded needlessly.
# distinctness – with respect to evolutionarily relevant criteria, i.e.
ecology
Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ...
,
morphology
Morphology, from the Greek and meaning "study of shape", may refer to:
Disciplines
* Morphology (archaeology), study of the shapes or forms of artifacts
* Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...
, or
biogeography
Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, ...
;
DNA sequences
A nucleic acid sequence is a succession of bases signified by a series of a set of five different letters that indicate the order of nucleotides forming alleles within a DNA (using GACT) or RNA (GACU) molecule. By convention, sequences are usua ...
are a ''consequence'' rather than a ''condition'' of diverging evolutionary lineages except in cases where they directly
inhibit
Inhibitor or inhibition may refer to:
In biology
* Enzyme inhibitor, a substance that binds to an enzyme and decreases the enzyme's activity
* Reuptake inhibitor, a substance that increases neurotransmission by blocking the reuptake of a neurotra ...
gene flow
In population genetics, gene flow (also known as gene migration or geneflow and allele flow) is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent a ...
(e.g.
postzygotic barrier
The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, behaviors and physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensure that any offspring ...
s).
Moreover, genera should be composed of
phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
units of the same kind as other (analogous) genera.
Etymology
The term "genus" comes from the
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
, a noun form
cognate
In historical linguistics, cognates or lexical cognates are sets of words in different languages that have been inherited in direct descent from an etymology, etymological ancestor in a proto-language, common parent language. Because language c ...
with ' ('to bear; to give birth to'). The Swedish taxonomist
Carl Linnaeus
Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...
popularized its use in his 1753 ''
Species Plantarum
' (Latin for "The Species of Plants") is a book by Carl Linnaeus, originally published in 1753, which lists every species of plant known at the time, classified into genera. It is the first work to consistently apply binomial names and was the ...
'', but the French botanist
Joseph Pitton de Tournefort
Joseph Pitton de Tournefort (5 June 165628 December 1708) was a French botanist, notable as the first to make a clear definition of the concept of genus for plants. Botanist Charles Plumier was his pupil and accompanied him on his voyages.
Lif ...
(1656–1708) is considered "the founder of the modern concept of genera".
Use
The scientific name (or the scientific epithet) of a genus is also called the generic name; in modern style guides and science it is always capitalised. It plays a fundamental role in
binomial nomenclature
In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...
, the system of naming
organism
In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
s, where it is combined with the scientific name of a
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
: see
Botanical name
A botanical name is a formal scientific name conforming to the '' International Code of Nomenclature for algae, fungi, and plants'' (ICN) and, if it concerns a plant cultigen, the additional cultivar or Group epithets must conform to the ''Intern ...
and
Specific name (zoology)
In zoological nomenclature, the specific name (also specific epithet or species epithet) is the second part (the second name) within the scientific name of a species (a binomen). The first part of the name of a species is the name of the genus or ...
.
Use in nomenclature
The rules for the
scientific name
In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...
s of
organism
In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
s are laid down in the
nomenclature codes
Nomenclature codes or codes of nomenclature are the various rulebooks that govern biological taxonomic nomenclature, each in their own broad field of organisms. To an end-user who only deals with names of species, with some awareness that species ...
, which allow each species a single unique name that, for
animal
Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...
s (including
protist
A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the exc ...
s),
plant
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...
s (also including
algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
and
fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
) and
prokaryote
A prokaryote () is a single-celled organism that lacks a nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Greek πρό (, 'before') and κάρυον (, 'nut' or 'kernel').Campbell, N. "Biology:Concepts & Connec ...
s (
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
and
archaea
Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...
), is
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
and binomial in form; this contrasts with
common or vernacular names, which are non-standardized, can be non-unique, and typically also vary by country and language of usage.
Except for
viruses
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsky's 1 ...
, the standard format for a
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
name comprises the generic name, indicating the genus to which the species belongs, followed by the specific epithet, which (within that genus) is unique to the species. For example, the
gray wolf
The wolf (''Canis lupus''; : wolves), also known as the gray wolf or grey wolf, is a large canine native to Eurasia and North America. More than thirty subspecies of ''Canis lupus'' have been recognized, and gray wolves, as popularly ...
's scientific name is with ''
Canis
''Canis'' is a genus of the Caninae which includes multiple extant species, such as wolves, dogs, coyotes, and golden jackals. Species of this genus are distinguished by their moderate to large size, their massive, well-developed skulls and den ...
'' (
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
for 'dog') being the generic name shared by the wolf's close relatives and (Latin for 'wolf') being the specific name particular to the wolf. A botanical example would be ''
Hibiscus arnottianus
Hawaiian hibiscus are seven species of hibiscus native to Hawaii. The yellow hibiscus is Hawaii's state flower. Most commonly grown as ornamental plants in the Hawaiian Islands are the non-native Chinese hibiscus (''Hibiscus rosa-sinensis'') and i ...
'', a particular species of the genus ''
Hibiscus
''Hibiscus'' is a genus of flowering plants in the mallow family, Malvaceae. The genus is quite large, comprising several hundred species that are native to warm temperate, subtropical and tropical regions throughout the world. Member species ...
'' native to Hawaii. The specific name is written in lower-case and may be followed by
subspecies
In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...
names in
zoology
Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the Animal, animal kingdom, including the anatomy, structure, embryology, evolution, Biological clas ...
or a variety of
infraspecific name
In botany, an infraspecific name is the scientific name for any taxon below the rank of species, i.e. an infraspecific taxon or infraspecies. (A "taxon", plural "taxa", is a group of organisms to be given a particular name.) The scientific names ...
s in
botany
Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...
.
When the generic name is already known from context, it may be shortened to its initial letter, for example ''C. lupus'' in place of ''Canis lupus''. Where species are further subdivided, the generic name (or its abbreviated form) still forms the leading portion of the scientific name, for example, for the
Eurasian wolf
The Eurasian wolf (''Canis lupus lupus''), also known as the common wolf,Mech, L. David (1981), ''The Wolf: The Ecology and Behaviour of an Endangered Species'', University of Minnesota Press, p. 354, is a subspecies of grey wolf native to Euro ...
subspecies, or as a botanical example, . Also, as visible in the above examples, the Latinised portions of the scientific names of genera and their included species (and infraspecies, where applicable) are, by convention, written in
italics
In typography, italic type is a cursive font based on a stylised form of calligraphic handwriting. Owing to the influence from calligraphy, italics normally slant slightly to the right. Italics are a way to emphasise key points in a printed tex ...
.
The scientific names of
virus
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsky's 1 ...
species are descriptive, not binomial in form, and may or may not incorporate an indication of their containing genus; for example, the virus species "
Salmonid herpesvirus 1
''Salmonid herpesvirus 1'' (SalHV-1) is a species of virus in the genus ''Salmonivirus'', family ''Alloherpesviridae'', and order ''Herpesvirales
The ''Herpesvirales'' is an order of dsDNA viruses (Baltimore group I) with animal hosts, charact ...
", "
Salmonid herpesvirus 2
''Salmonid herpesvirus 2'' (SalHV-2) is a species of virus in the genus ''Salmonivirus'', family ''Alloherpesviridae'', and order ''Herpesvirales
The ''Herpesvirales'' is an order of dsDNA viruses (Baltimore group I) with animal hosts, charact ...
" and "
Salmonid herpesvirus 3
''Salmonid herpesvirus 3'' (SalHV-3) is a species of virus in the genus '' Salmonivirus'', family '' Alloherpesviridae'', and order ''Herpesvirales
The ''Herpesvirales'' is an order of dsDNA viruses (Baltimore group I) with animal hosts, chara ...
" are all within the genus ''
Salmonivirus
''Salmonivirus'' is a genus of viruses in the order ''Herpesvirales'', in the family '' Alloherpesviridae''. Salmonidae serve as natural hosts. There are three species in this genus. Diseases associated with this genus include: salHV-3: epizootic ...
'', however, the genus to which the species with the formal names "
Everglades virus
''Everglades virus'' (EVEV) is an alphavirus included in the Venezuelan equine encephalitis virus complex. The virus circulates among rodents and vector mosquitoes and sometimes infects humans, causing a febrile illness with occasional neurologic ...
" and "
Ross River virus
''Ross River virus'' (RRV) is a small encapsulated single-strand RNA ''Alphavirus'' endemic to Australia, Papua New Guinea and other islands in the South Pacific. It is responsible for a type of mosquito-borne non-lethal but extremely debilita ...
" are assigned is ''
Alphavirus
''Alphavirus'' is a genus of RNA viruses, the sole genus in the ''Togaviridae'' family. Alphaviruses belong to group IV of the Baltimore classification of viruses, with a positive-sense, single-stranded RNA genome. There are 32 alphaviruses, ...
''.
As with scientific names at other ranks, in all groups other than viruses, names of genera may be cited with their authorities, typically in the form "author, year" in zoology, and "standard abbreviated author name" in botany. Thus in the examples above, the genus ''Canis'' would be cited in full as "''Canis'' Linnaeus, 1758" (zoological usage), while ''Hibiscus'', also first established by
Linnaeus
Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...
but in 1753, is simply "''Hibiscus'' L." (botanical usage).
The type concept
Each genus should have a designated
type, although in practice there is a backlog of older names without one. In zoology, this is the
type species
In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...
, and the generic name is permanently associated with the
type specimen
In biology, a type is a particular wiktionary:en:specimen, 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 a ...
of its type species. Should the specimen turn out to be assignable to another genus, the generic name linked to it becomes a
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 ...
and the remaining
taxa
In biology, a taxon (back-formation from ''taxonomy''; plural 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 nam ...
in the former genus need to be reassessed.
Categories of generic name
In zoological usage, taxonomic names, including those of genera, are classified as "available" or "unavailable". Available names are those published in accordance with 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 ...
; the earliest such name for any taxon (for example, a genus) should then be selected as the "
valid" (i.e., current or accepted) name for the taxon in question.
Consequently, there will be more available names than valid names at any point in time, which names are currently in use depending on the judgement of taxonomists in either combining taxa described under multiple names, or splitting taxa which may bring available names previously treated as synonyms back into use. "Unavailable" names in zoology comprise names that either were not published according to the provisions of the ICZN Code, e.g., incorrect original or subsequent spellings, names published only in a thesis, and generic names published after 1930 with no type species indicated.
According to "Glossary" section of the zoological Code, suppressed ''names'' (per published "Opinions" of the International Commission of Zoological Nomenclature) remain available but cannot be used as the valid name for a taxon, however the names published in suppressed ''works'' are made unavailable via the relevant Opinion dealing with the work in question.
In botany, similar concepts exist but with different labels. The botanical equivalent of zoology's "available name" is a
validly published name
In botanical nomenclature, a validly published name is a name that meets the requirements in the '' International Code of Nomenclature for algae, fungi, and plants'' for valid publication. Valid publication of a name represents the minimum requir ...
. An invalidly published name is a ' or '; a rejected name is a ' or '; a later homonym of a validly published name is a ' or '; for a full list refer to the
''International Code of Nomenclature for algae, fungi, and plants'' and the work cited above by Hawksworth, 2010.
In place of the "valid taxon" in zoology, the nearest equivalent in botany is "
correct name
In botany, the correct name according to the International Code of Nomenclature for algae, fungi, and plants (ICN) is the one and only botanical name that is to be used for a particular taxon, when that taxon has a particular circumscription, posit ...
" or "current name" which can, again, differ or change with alternative taxonomic treatments or new information that results in previously accepted genera being combined or split.
Prokaryote
A prokaryote () is a single-celled organism that lacks a nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Greek πρό (, 'before') and κάρυον (, 'nut' or 'kernel').Campbell, N. "Biology:Concepts & Connec ...
and
virus
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsky's 1 ...
codes of nomenclature also exist which serve as a reference for designating currently accepted genus names as opposed to others which may be either reduced to synonymy, or, in the case of prokaryotes, relegated to a status of "names without standing in prokaryotic nomenclature".
An available (zoological) or validly published (botanical) name that has been historically applied to a genus but is not regarded as the accepted (current/valid) name for the taxon is termed a
synonym
A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
; some authors also include unavailable names in lists of synonyms as well as available names, such as misspellings, names previously published without fulfilling all of the requirements of the relevant nomenclatural code, and rejected or suppressed names.
A particular genus name may have zero to many synonyms, the latter case generally if the genus has been known for a long time and redescribed as new by a range of subsequent workers, or if a range of genera previously considered separate taxa have subsequently been consolidated into one. For example, the
World Register of Marine Species
The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive list of names of marine organisms.
Content
The content of the registry is edited and maintained by scientific specialist ...
presently lists 8 genus-level synonyms for the sperm whale genus ''
Physeter
''Physeter'' is a genus of toothed whales. There is only one living species in this genus: the sperm whale (''Physeter macrocephalus''). Some extremely poorly known fossil species have also been assigned to the same genus including ''Physeter an ...
'' Linnaeus, 1758, and 13 for the bivalve genus ''
Pecten'' O.F. Müller, 1776.
Identical names (homonyms)
Within the same kingdom, one generic name can apply to one genus only. However, many names have been assigned (usually unintentionally) to two or more different genera. For example, the
platypus
The platypus (''Ornithorhynchus anatinus''), sometimes referred to as the duck-billed platypus, is a semiaquatic, egg-laying mammal Endemic (ecology), endemic to Eastern states of Australia, eastern Australia, including Tasmania. The platypu ...
belongs to the genus ''Ornithorhynchus'' although
George Shaw George Shaw may refer to:
* George Shaw (biologist) (1751–1813), English botanist and zoologist
* George B. Shaw (1854–1894), U.S. Representative from Wisconsin
* George Bernard Shaw (1856–1950), Irish playwright
* George C. Shaw (1866–196 ...
named it ''Platypus'' in 1799 (these two names are thus ''synonyms''). However, the name ''Platypus'' had already been given to a group of
ambrosia beetle
Ambrosia beetles are beetles of the weevil subfamilies Scolytinae and Platypodinae ( Coleoptera, Curculionidae), which live in nutritional symbiosis with ambrosia fungi. The beetles excavate tunnels in dead, stressed, and healthy trees in wh ...
s by
Johann Friedrich Wilhelm Herbst
Johann Friedrich Wilhelm Herbst (1 November 1743 – 5 November 1807) was a German naturalist and entomologist from Petershagen, Minden-Ravensberg. He served as a chaplain in the Prussian army. His marriage in Berlin, 1770, with Euphrosyne Luise ...
in 1793. A name that means two different things is a ''homonym''. Since beetles and platypuses are both members of the kingdom Animalia, the name could not be used for both.
Johann Friedrich Blumenbach
Johann Friedrich Blumenbach (11 May 1752 – 22 January 1840) was a German physician, naturalist, physiologist, and anthropologist. He is considered to be a main founder of zoology and anthropology as comparative, scientific disciplines. He wa ...
published the replacement name ''Ornithorhynchus'' in 1800.
However, a genus in one
kingdom
Kingdom commonly refers to:
* A monarchy ruled by a king or queen
* Kingdom (biology), a category in biological taxonomy
Kingdom may also refer to:
Arts and media Television
* ''Kingdom'' (British TV series), a 2007 British television drama s ...
is allowed to bear a scientific name that is in use as a generic name (or the name of a taxon in another rank) in a kingdom that is governed by a different nomenclature code. Names with the same form but applying to different taxa are called "homonyms". Although this is discouraged by both 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 ...
and the
, there are some five thousand such names in use in more than one kingdom. For instance,
* ''
Anura'' is the name of the
order
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
of frogs but also is the name of a
non-current genus of plants;
* ''Aotus'' is the generic name of both
golden peas and
night monkey
Night monkeys, also known as owl monkeys or douroucoulis (), are nocturnal New World monkeys of the genus ''Aotus'', the only member of the family Aotidae (). The genus comprises eleven species which are found across Panama and much of South Ame ...
s;
* ''Oenanthe'' is the generic name of both
wheatear
The wheatears are passerine birds of the genus ''Oenanthe''. They were formerly considered to be members of the thrush family, Turdidae, but are now more commonly placed in the flycatcher family, Muscicapidae. This is an Old World group, bu ...
s and
water dropwort
Water dropwort is a common name for several genera of plants and may refer to:
* ''Oenanthe'' (plant)
* ''Oxypolis
''Oxypolis'' is a small genus of North American flowering plants in the carrot family known as cowbane, water dropwort, dropwort ...
s;
* ''Prunella'' is the generic name of both
accentor
The accentors are a genus of birds in the family Prunellidae, which is endemic to the Old World. This small group of closely related passerines are all in the genus ''Prunella''. All but the dunnock and the Japanese accentor are inhabitants of th ...
s and
self-heal
''Prunella'' is a genus of herbaceous plants in the family Lamiaceae, also known as self-heals, heal-all, or allheal for their use in herbal medicine.
Habitat
Most are native to Europe, Asia, and North Africa, but ''Prunella vulgaris'' (common ...
; and
* ''Proboscidea'' is the order of
elephant
Elephants are the largest existing land animals. Three living species are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantidae an ...
s and the genus of
devil's claws.
* The name of the genus ''
Paramecia'' (an extinct red alga) is also the plural of the name of the genus ''
Paramecium
''
''Paramecium'' ( , ; also spelled ''Paramoecium'') is a genus of eukaryotic, unicellular ciliates, commonly studied as a representative of the ciliate group. ''Paramecia'' are widespread in freshwater, brackish, and marine environments and a ...
'' (which is in the SAR supergroup), which can also lead to confusion.
A list of generic homonyms (with their authorities), including both available (validly published) and selected unavailable names, has been compiled by the
Interim Register of Marine and Nonmarine Genera
The Interim Register of Marine and Nonmarine Genera (IRMNG) is a taxonomic database which attempts to cover published genus names for all domains of life from 1758 in zoology (1753 in botany) up to the present, arranged in a single, internally c ...
(IRMNG).
Use in higher classifications
The
type genus
In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name.
Zoological nomenclature
According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal f ...
forms the base for higher
taxonomic
Taxonomy is the practice and science of categorization or classification.
A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...
ranks, such as the family name ("Canids") based on ''Canis''. However, this does not typically ascend more than one or two levels: the
order
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
to which dogs and wolves belong is ("Carnivores").
Numbers of accepted genera
The numbers of either accepted, or all published genus names is not known precisely; Rees et al., 2020 estimate that approximately 310,000 accepted names (valid taxa) may exist, out of a total of c. 520,000 published names (including synonyms) as at end 2019, increasing at some 2,500 published generic names per year. "Official" registers of taxon names at all ranks, including genera, exist for a few groups only such as viruses
and prokaryotes, while for others there are compendia with no "official" standing such as ''
Index Fungorum
''Index Fungorum'' is an international project to index all formal names ( scientific names) in the fungus kingdom. the project is based at the Royal Botanic Gardens, Kew, one of three partners along with Landcare Research and the Institute of M ...
'' for fungi, ''Index Nominum Algarum'' and
AlgaeBase
AlgaeBase is a global species database of information on all groups of algae, both marine and freshwater, as well as sea-grass.
History
AlgaeBase began in March 1996, founded by Michael Guiry. Text was copied from this source, which is avai ...
for algae, ''Index Nominum Genericorum'' and the
International Plant Names Index
The International Plant Names Index (IPNI) describes itself as "a database of the names and associated basic bibliographical details of seed plants, ferns and lycophytes." Coverage of plant names is best at the rank of species and genus. It inclu ...
for plants in general, and ferns through angiosperms, respectively, and ''
Nomenclator Zoologicus
' is one of the major compendia (in this case, of the names of genera and subgenera) in the field of zoological nomenclature, compiled by Sheffield Airey Neave and his successors and published in 9 volumes over the period 1939–1994, under the a ...
'' and the
Index to Organism Names
The Index to Organism Names (ION) is an extensive compendium of scientific names of taxa at all ranks in the field of zoology, compiled from the Zoological Record (later supplemented with content from Sherborn's ''Index Animalium'') by its operator ...
for zoological names.
Totals for both "all names" and estimates for "accepted names" as held in the ''
Interim Register of Marine and Nonmarine Genera
The Interim Register of Marine and Nonmarine Genera (IRMNG) is a taxonomic database which attempts to cover published genus names for all domains of life from 1758 in zoology (1753 in botany) up to the present, arranged in a single, internally c ...
'' (IRMNG) are broken down further in the publication by Rees et al., 2020 cited above. The accepted names estimates are as follows, broken down by kingdom:
![Estimated accepted genus totals by kingdom - based on Rees et al 2020](https://upload.wikimedia.org/wikipedia/commons/f/f9/Estimated_accepted_genus_totals_by_kingdom_-_based_on_Rees_et_al_2020.jpg)
*
Animal
Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...
ia: 239,093 accepted genus names (± 55,350)
*
Plant
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...
ae: 28,724 (± 7,721)
*
Fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
: 10,468 (± 182)
*
Chromista
Chromista is a biological kingdom consisting of single-celled and multicellular eukaryotic species that share similar features in their photosynthetic organelles (plastids). It includes all protists whose plastids contain chlorophyll ''c'', such ...
: 11,114 (± 1,268)
*
Protozoa
Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...
: 3,109 (± 1,206)
*
Bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
: 3,433 (± 115)
*
Archaea
Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...
: 140 (± 0)
*
Virus
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsky's 1 ...
es: 851 (± 0)
The cited ranges of uncertainty arise because IRMNG lists "uncertain" names (not researched therein) in addition to known "accepted" names; the values quoted are the mean of "accepted" names alone (all "uncertain" names treated as unaccepted) and "accepted + uncertain" names (all "uncertain" names treated as accepted), with the associated range of uncertainty indicating these two extremes.
Within Animalia, the largest phylum is
Arthropod
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...
a, with 151,697 ± 33,160 accepted genus names, of which 114,387 ± 27,654 are
insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...
s (class Insecta). Within Plantae,
Tracheophyta
Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They al ...
(vascular plants) make up the largest component, with 23,236 ± 5,379 accepted genus names, of which 20,845 ± 4,494 are
angiosperms
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...
(superclass Angiospermae).
By comparison, the 2018 annual edition of the
Catalogue of Life
The Catalogue of Life is an online database that provides an index of known species of animals, plants, fungi, and microorganisms. It was created in 2001 as a partnership between the global Species 2000 and the American Integrated Taxonomic Info ...
(estimated >90% complete, for extant species in the main) contains currently 175,363 "accepted" genus names for 1,744,204 living and 59,284 extinct species, also including genus names only (no species) for some groups.
Genus size
![Number of reptile genera with a given number of species](https://upload.wikimedia.org/wikipedia/commons/7/7d/Number_of_reptile_genera_with_a_given_number_of_species.png)
The number of species in genera varies considerably among taxonomic groups. For instance, among (non-avian)
reptile
Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...
s, which have about 1180 genera, the most (>300) have only 1 species, ~360 have between 2 and 4 species, 260 have 5–10 species, ~200 have 11–50 species, and only 27 genera have more than 50 species. However, some insect genera such as the bee genera ''
Lasioglossum
The sweat bee genus ''Lasioglossum'' is the largest of all bee genera, containing over 1700 species in numerous subgenera worldwide.Gibbs, J., et al. (2012)Phylogeny of halictine bees supports a shared origin of eusociality for ''Halictus'' an ...
'' and ''
Andrena
''Andrena'' is a genus of bees in the family Andrenidae. With over 1,500 species, it is one of the largest genera of animals. It is a strongly monophyletic group that is difficult to split into more manageable divisions; currently, ''Andrena'' i ...
'' have over 1000 species each. The largest flowering plant genus, ''
Astragalus
''Astragalus'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to tempe ...
'', contains over 3,000 species.
Which species are assigned to a genus is somewhat arbitrary. Although all species within a genus are supposed to be "similar", there are no objective criteria for grouping species into genera. There is much debate among zoologists whether enormous, species-rich genera should be maintained, as it is extremely difficult to come up with identification keys or even character sets that distinguish all species. Hence, many taxonomists argue in favor of breaking down large genera. For instance, the lizard genus ''
Anolis
''Anolis'' is a genus of anoles (), iguanian lizards in the family Dactyloidae, native to the Americas. With more than 425 species, it represents the world's most species-rich amniote tetrapod genus, although many of these have been proposed to ...
'' has been suggested to be broken down into 8 or so different genera which would bring its ~400 species to smaller, more manageable subsets.
See also
*
List of the largest genera of flowering plants
There are over 56 genera of flowering plants estimated to contain at least 500 described species. The largest of these is currently the legume genus ''Astragalus'' (milk-vetches), with over 3,000 species.
The sizes of plant genera vary widely fr ...
References
External links
Interim Register of Marine and Nonmarine Genera (IRMNG) includes an estimated 95% of published genus names (accepted and unaccepted) in all groups (semi-continuously updated)
''Nomenclator Zoologicus'': index of genus and subgenus names (accepted and unaccepted) in zoological nomenclature from 1758 to 2004
Index to Organism Names includes zoological taxon names at all ranks (including genera) as continuously indexed for the
''Zoological Record''
''Index Nominum Genericorum'' (ING) a compilation of generic names (accepted and unaccepted) published for organisms covered by the ICN: International Code of Nomenclature for Algae, Fungi, and Plants (semi-continuously updated)
LPSN – List of Prokaryotic names with Standing in Nomenclature includes all currently accepted Bacteria and Archaea genus names (continuously updated)
ICTV taxonomy releases latest and historical lists of accepted virus names compiled by the International Committee on Taxonomy of Viruses (ICTV), including all currently accepted virus genus names (updated via regular releases)
{{Taxonomic ranks
*01
Genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
Plant taxonomy
Zoological nomenclature
Bacterial nomenclature
Taxa named by Joseph Pitton de Tournefort