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 International Commission on
Zoological Nomenclature (which shares the acronym "ICZN"). The rules
How names are correctly established in the frame of binominal
Which name must be used in case of name conflicts
How scientific literature must cite names
Zoological nomenclature is independent of other systems of
nomenclature, for example botanical nomenclature. This implies that
animals can have the same generic names as plants.
The rules and recommendations have one fundamental aim: to provide the
maximum universality and continuity in the naming of all animals,
except where taxonomic judgment dictates otherwise. The code is meant
to guide only the nomenclature of animals, while leaving zoologists
freedom in classifying new taxa.
In other words, whether a species itself is or is not a recognized
entity is a subjective decision, but what name should be applied to it
is not. The code applies only to the latter. A new animal name
published without adherence to the code may be deemed simply
"unavailable" if it fails to meet certain criteria, or fall entirely
out of the province of science (e.g., the "scientific name" for the
Loch Ness Monster).
The rules in the code determine what names are valid for any taxon in
the family group, genus group, and species group. It has additional
(but more limited) provisions on names in higher ranks. The code
recognizes no case law. Any dispute is decided first by applying the
code directly, and not by reference to precedent.
The code is also retroactive or retrospective, which means that
previous editions of the code, or previous other rules and conventions
have no force any more today, and the nomenclatural acts published
'back in the old times' must be evaluated only under the present
edition of the code. In cases of disputes concerning the
interpretation, the usual procedure is to consult the French Code,
lastly a case can be brought to the commission who has the right to
publish a final decision.
1.1 Principle of binominal nomenclature
1.2 Principle of priority
1.3 Principle of coordination
1.4 Principle of the first reviser
1.5 Principle of homonymy
1.6 Principle of typification
2.1 Gender agreement
5 Local usage and name changes
8 See also
10 External links
In regulating the names of animals it holds by six central principles,
which were first set out (as principles) in the third edition of the
Principle of binominal nomenclature
This is the principle that the scientific name of a species, and not
of a taxon at any other rank, is a combination of two names; the use
of a trinomen for the name of a subspecies and of uninominal names for
taxa above the species group is in accord with this principle.
This means that in the system of nomenclature for animals, the name of
a species is composed of a combination of a generic name and a
specific name; together they make a "binomen". No other rank can
have a name composed of two names. Examples:
Subspecies have a name composed of three names, a "trinomen": generic
name, specific name, subspecific name:
Giraffa camelopardalis rothschildi
Taxa at a rank above species have a name composed of one name, a
Genus Giraffa, family Giraffidae
In botanical nomenclature, the equivalent for "binominal nomenclature"
is "binary nomenclature" (or sometimes "binomial nomenclature").
Principle of priority
Main article: Principle of Priority
This is the principle that the correct formal scientific name for an
animal taxon, the valid name, correct to use, is the oldest available
name that applies to it. It is the most important principle—the
fundamental guiding precept that preserves zoological nomenclature
stability. It was first formulated in 1842 by a committee appointed by
British Association to consider the rules of zoological
Hugh Edwin Strickland
Hugh Edwin Strickland wrote the committee's report.
Nunneley 1837 established
Limax maculatus (Gastropoda), Wiktor 2001
classified it as a junior synonym of
Limax maximus Linnæus 1758 from
S and W Europe.
Limax maximus was established first, so if Wiktor's
2001 classification is accepted,
Limax maximus takes precedence over
Limax maculatus and must be used for the species.
There are approximately 2-3 million cases of this kind for which this
principle is applied in zoology.
Principle of coordination
The principle of coordination is that within the family group, genus
group and species group, a name established for a taxon at any rank in
the group is simultaneously established with the same author and date
for taxa based on the same name-bearing type at other ranks in the
corresponding group. In other words, publishing a new zoological
name automatically and simultaneously establishes all corresponding
names in the relevant other ranks with the same type.
In the species-group, publishing a species name (the binomen) Giraffa
camelopardalis Linnaeus, 1758 also establishes the subspecies name
Giraffa camelopardalis camelopardalis Linnaeus, 1758.
The same applies to the name of a subspecies; this establishes the
corresponding species name.
In the genus-group, similarly, publishing the name of a genus also
establishes the corresponding name of a subgenus (or vice versa):
Giraffa Linnaeus, 1758 and subgenus
Giraffa (Giraffa) Linnaeus,
In the family-group, publication of the name of a family, subfamily,
superfamily (or any other such rank) also establishes the names in all
the other ranks in the family group (family Giraffidae, superfamily
Giraffoidea, subfamily Giraffinae).
Author citations for such names (for example a subgenus) are the same
as for the name actually published (for example a genus). It is
immaterial if there is an actual taxon to which the automatically
established name applies; if ever such a taxon is recognised, there is
a name available for it.
Principle of the first reviser
This is the principle that in cases of conflicts between
simultaneously published divergent acts, the first subsequent author
can decide which has precedence. It supplements the principle of
priority, which states that the first published name takes precedence.
The principle of the first reviser deals with situations that cannot
be resolved by priority. These items may be two or more different
names for the same taxon, two or more names with the same spelling
used for different taxa, two or more different spellings of a
particular name, etc. In such cases, the first subsequent author who
deals with the matter and chooses and publishes the decision in the
required manner is the first reviser, and is to be followed.
Linnæus 1758 established Strix scandiaca and Strix noctua (Aves), for
which he gave different descriptions and referred to different types,
but both taxa later turned out to refer to the same species, the snowy
owl. The two names are subjective synonyms. Lönnberg 1931 acted as
first reviser, cited both names and selected Strix scandiaca to have
A problem is that sometimes the first reviser is unknown. For the
sperm whale Linnæus 1758 established three subjective synonyms,
Physeter macrocephalus, Physeter catodon, and Physeter microps. The
first reviser remains unknown; both Ph. macrocephalus and Ph. catodon
Principle of homonymy
This is the principle that the name of each taxon must be unique.
Consequently, a name that is a junior homonym of another name must not
be used as a valid name.
It means that any one animal name, in one particular spelling, may be
used only once (within its group). This is usually the first-published
name; any later name with the same spelling (a homonym) is barred from
being used. The principles of priority and first reviser apply here.
For family-group names the termination (which is rank-bound) is not
taken into account.
Genera are homonyms only if exactly the same — a one-letter
difference is enough to distinguish them.
Argus Bohadsch, 1761 (Gastropoda) (was made available for homonymy by
ICZN in Opinion 429, Bohadsch 1761 was non-binominal - this had the
effect that no other one of the various following names Argus can be
used for a taxon)
Argus Scopoli, 1763 (Lepidoptera: Lycaenidae: Polyommatinae)
Argus Scopoli, 1777 (Lepidoptera: Nymphalidae: Satyrinae)
Argus Poli, 1791 (Bivalvia)
Argus Temminck, 1807 (Aves)
Argus Lamarck, 1817 (Lepidoptera: Hesperiidae)
Argus Walckenaer, 1836 (Araneae)
Argus Gerhard, 1850 (Lepidoptera: Lycaenidae: Theclinae)
Homonyms of Argus are not:
Argua Walker, 1863 (Lepidoptera), Argusa Kelham, 1888 (Aves), Argusina
Hebard, 1927 (Dermaptera), Arcus Hong, 1983 (Diptera), Argas
Latreille, 1795 (Araneae),
Argulus Müller, 1785 (Crustacea).
Homonyms are not: Isomya Cutler & Cutler, 1985 (Sipunculida),
Isomyia Walker, 1859 (Diptera).
Homonyms are not: Adelomya Mulsant & Verreaux, 1866 (Aves),
Adelomyia Bonaparte, 1854 (Aves), Adelomys Gervais, 1853 (Mammalia),
Adolomys Shevyreva, 1989 (Mammalia), Adulomya Kuroda, 1931 (Bivalvia).
In species, there is a difference between primary and secondary
homonyms. There can also be double homonyms (same genus and species).
A slight difference in spelling is tolerated if Article 58 applies.
Primary homonyms are those with the same genus and same species in
their original combination. The difference between a primary junior
homonym and a subsequent use of a name is undefined, but it is
commonly accepted that if the name referred to another species or
form, and if there is in addition no evidence the author knew that the
name was previously used, it is considered as a junior homonym.
Drury (1773) established
Cerambyx maculatus (Coleoptera) for a species
from Jamaica. Fueßlin (1775) established
Cerambyx maculatus for a
different species from Switzerland, and did not refer to Drury's name.
Fueßlin's name is a junior primary homonym.
Scopoli (1763) established Curculio fasciatus (Coleoptera) for a
species from Slovenia. Strøm (1768) established Curculio fasciatus
for another species from Norway. De Geer (1775) established Curculio
fasciatus for a 3rd species from Sweden. Müller (1776) established
Curculio fasciatus for a 4th species from Denmark. Fourcroy (1785)
established Curculio fasciatus for a 5th species from France. Olivier
(1790) established Curculio fasciatus for a 6th species from France.
Marsham (1802) established Curculio fasciatus for a 7th species from
Britain. All these names had descriptions that clarified that
different species were meant, and that their authors did not know that
the name had been established by a previous author.
Secondary homonyms can be produced if taxa with the same specific name
but different original genus are later classified in the same genus
(Art. 57.3, 59). A secondary synonym[clarification needed] is only a
temporary state, it is only effective in this classification. If
another classification is applied, the secondary homonymy may not be
produced, and the involved name can be used again (Art. 59.1). A name
does not become unavailable or unusable if it was once in the course
of history placed in such a genus where it produced a secondary
homonymy with another name. This is one of the rare cases where a
zoological species does not have a stable specific name and a unique
species-author-year combination, it can have two names at the same
Nunneley (1837) established
Limax maculatus (Gastropoda), Wiktor
(2001) classified it as a junior synonym of
Limax (Limax) maximus
Linnæus, 1758 from S and W Europe. Kaleniczenko, 1851 established
Krynickillus maculatus for a different species from Ukraine. Wiktor,
2001 classified both
Limax maximus Linnæus, 1758 and Krynickillus
maculatus Kaleniczenko, 1851 in the genus Limax. This meant that L.
maculatus Nunneley, 1837 and K. maculatus Kaleniczenko, 1851 were
classified in the same genus, so both names were secondary homonyms in
the genus Limax, and the younger name (from 1851) could not be used
for the Ukrainian species. This made it necessary to look for the next
younger available name that could be used for the Ukrainian species.
Limax ecarinatus Boettger, 1881, a junior synonym of K.
maculatus Kaleniczenko, 1851.
For Wiktor (2001) and those authors who follow Wiktor's system the
name of the Ukrainian species must be
Limax ecarinatus Boettger, 1881.
For the others who classify
Limacus as a separate genus, the name of
the Ukrainian species must be
Limacus maculatus (Kaleniczenko, 1851).
So the Ukrainian species can have two names, depending from its
Limacus maculatus, the same
Article 59.3 states that in exceptional cases, junior secondary
homonyms replaced before 1961 by substitute names can become invalid,
"...unless the substitute name is not in use," an exception of the
exception. However, the ICZN Code does not give an example for such a
case. It seems that this passage in the ICZN Code is widely ignored.
It also does not define what the expression "is not in use" should
Glischrus caelata Studer, 1820 (Gastropoda) was once classified in the
genus Helix, and became a junior secondary homonym of Helix caelata
[Vallot], 1801. Locard (1880) established a replacement name Helix
glypta, which has very rarely been used. The species is now known as
Trochulus caelatus (Studer, 1820), and Art. 59.3 is commonly
Double homonymy (genus and species) is no homonymy: if the genera are
homonyms and belong to different animal groups, the same specific
names can be used in both groups.
The name Noctua Linnæus, 1758 was established for a lepidopteran
subgenus. In 1764 he established a genus Noctua Linné ,1764 for
birds, ignoring that he had already used this name a few years ago in
Lepidoptera. Noctua Linné, 1764 (Aves) is a junior homonym of Noctua
Linnæus, 1758 (Lepidoptera).
Garsault (1764) used Noctua for a bird and established a name Noctua
caprimulgus Garsault, 1764 (Aves). Fabricius (1775) established a name
Noctua caprimulgus Fabricius, 1775 (Lepidoptera), thus creating a
double homonym. Double homonymy is no homonymy, both names are
The same happened with
Noctua variegata Jung, 1792 (Lepidoptera) and
Noctua variegata Quoy & Gaimard, 1830 (Aves).
For disambiguating one genus-group name from its homonym, it is
important to cite author and year. Citing the author alone is often
Echidna Forster, 1777 (Actinopterygii), not
Echidna Cuvier, 1797
Ansa Walker, 1858 (Lepidoptera), not Ansa Walker, 1868 (Hemiptera)
Helix balcanica Kobelt, 1876, not Helix balcanica Kobelt, 1903 (both
Conus catenatus Sowerby, 1850, not Conus catenatus Sowerby, 1875 (both
The name Ansa can only be used for a lepidopteran taxon. If that name
cannot be used (for example because an older name established prior to
1858 takes precedence), this does not mean that the 1868 name can be
used for a hemipteran genus. The only option to use the 1868 name for
the hemipteran taxon is to get the 1858 name officially suppressed by
In some cases, the same genus-group or species-group name was
published in the same year by the same author. In these cases it is
useful to cite the page where the name was established.
Amydona Walker, 1855 (Lepidoptera: Limacodidae) (p. 1110), not Amydona
Walker, 1855 (Lepidoptera: Lasiocampidae) (p. 1413)
Betousa Walker, 1865 (Lepidoptera: Thyridae) (p. 1111), not Betousa
Walker, 1865 (Lepidoptera: Noctuidae) (p. 1208).
Cicada variegata Fabricius, 1775 (p. 684), not Cicada variegata
Fabricius, 1775 (p. 686) (both Auchenorrhyncha).
Noctua marginata Fabricius, 1775 (p. 597), not Noctua marginata
Fabricius, 1775 (p. 610) (both Lepidoptera: Noctuidae).
Clausilia (Albinaria) oertzeni Boettger, 1889 (p. 42), not Clausilia
(Albinaria) schuchi var. oertzeni Boettger, 1889 (p. 52) (both
There are cases where two homonyms were established by the same author
in the same year on the same page:
Zonites verticillus var. graeca Kobelt, 1876 (Gastropoda) (p. 48), not
Zonites albanicus var. graeca Kobelt, 1876 (p. 48).
Animal, plant, and fungi nomenclature are entirely independent from
each other. The most evident shortcoming of this situation (for their
use in biodiversity informatics) is that the same generic name can be
used simultaneously for animals and plants. For this kind of homonym
the expression "hemihomonym" is sometimes used. Far more than 1000
such names are known.
The generic name Dryas L. (1753) represents a genus of magnoliophytan
plants (family Rosaceae), and at the same time Dryas Hübner, 1807 is
also a lepidopteran insect genus (family Nymphalidae).
Tandonia was established in animals (Gastropoda: Tandonia),
in plants (Euphorbiaceae) and in Fungi (Ascomycetes).
Other examples for sometimes well known plant names with zoological
equivalents are Aotus (Fabaceae and Mammalia), Arenaria
(Caryophyllaeceae and Aves), Betula(Betulaceae and Hymenoptera),
Chloris (Cactaceae and Aves), Dugesia (Asteraceae and Plathelminthes),
Erica (Ericaceae and Araneae), Hystrix (Poaceae and Mammalia), Iris
(Asparagales and Orthoptera), Liparis (Orchidaceae and
Actinopterygii), Phalaenopsis (Asparagales and Aves), Pinus (Pinaceae
and Mollusca), Prunella (Lamiaceae and Aves), Ricinus (Fabaceae and
Acari), Taxus (Taxaceae and Mammalia), Typha (Typhaceae and Porifera),
Ulva (Ulvophyceae and Lepidoptera), Viola (Violaceae and Lepidoptera).
For names above the family level, the principle of homonymy does not
Pulmonata is usually used for a very prominent group in Gastropoda,
but the name is also (rarely) used for a group in Arachnida.
Reticulata is used as an order in Foraminifera, and as an undefined
higher group in Ephemeroptera.
Homonyms occur relatively rarely in families (only if generic names
are identical or very similar and adding an ending "-idae" produces
identical results). Discovering such a homonymy usually produces the
same problems as if there were no rules: conflicts between entirely
independent and unconnected groups of taxonomists working in different
animal groups. Very often the Commission must be asked to take a
Bulimina (Foraminifera) and
Buliminus (Gastropoda) give both
Buliminidae, and both families were used since the 1880s. When the
homonymy was discovered 110 years later in the 1990s, the younger
(gastropod) taxon had to receive a new family name, and the commission
needed was asked for a solution (Opinion 2018).
Claria (Rotifera) and
Clarias (Actinopterygii) give both Clariidae,
but only the actinopterygian fish name was used since 1845. Shortly
after Clariidae had been proposed in Rotifera in 1990, the homonymy
was discovered and the commission had to decide that the Rotiferan
family had to be amended to Clariaidae (Opinion 2032).
Principle of typification
This is the principle that each nominal taxon in the family group,
genus group, or species group has—actually or potentially—a
name-bearing type fixed that provides the objective standard of
reference that determines what the name applies to.
This means that any named taxon has a name-bearing type, which allows
the objective application of that name. Any family-group name must
have a type genus, any genus-group name must have a type species, and
any species-group name can (not must) have one or more type specimens
(holotype, lectotype, neotype, syntypes, or others), usually deposited
in a museum collection. The type genus for a family-group name is
simply the genus that provided the stem to which was added the ending
"-idae" (for families). Example:
The family name
Spheniscidae has as its type genus the genus
Spheniscus Brisson, 1760.
The type species for a genus-group name is more complicated and
follows exactly defined provisions in articles 67-69.
Type species are
very important, and no general zoological database has recorded the
type species for all genera. Except in fishes and some minor groups,
type species are rarely reliably recorded in online animal databases.
In 60% of the cases the type species can be determined in the original
publication. The type species is always the original name of the taxon
(and not the currently used combination).
The correctly cited type species of
Locusta Linnæus, 1758 (Caelifera)
is Gryllus migratorius Linnæus, 1758, not
Designation and fixation have different meanings. A designation is the
proposal of the type species. It is not necessary to have spelled the
name of the genus or species correctly with correct authors (articles
67.2.1, 67.6, 67.7), type species are always the correctly spelled
name. If the designation is valid, the type species is fixed.
A designation can also be invalid and ineffective—for example—if
the genus had already a previously fixed type species, or if a type
species was proposed that was not originally included, or contradicted
the description or figure for a genus for which no species had
originally been included.
There are various possible modes of type species designation. This is
their order of legal importance, with approximate proportions of
occurrence and examples:
Superior type fixation:
Designation by ICZN under the plenary powers (3 %)
Galba Schrank, 1803 (Gastropoda) was established with one species
Galba pusilla Schrank, 1803. This would be the type species
by monotypy. In Opinion 1896 (published in 1998) this type fixation
was set aside and Buccinum truncatulum Müller, 1774 was fixed as type
species under the plenary power(s) (now
Designation under Art. 70.3 (misidentified type species) (1 %)
Bollingeria Forcart, 1940 (Gastropoda) was established with its type
species Chondrus pupoides Krynicki, 1833 proposed by original
designation. But Forcart 1940 misidentified the type species and meant
Bulimus lamelliferus Rossmässler, 1858. It would be convenient to
designate Bulimus lamelliferus as type species under Art. 70.3.
Helisoma Swainson, 1840 (Gastropoda) was established with one species
included, cited by Swainson as "H. bicarinata Sow. Gen. f. 4". This
suggested that the type species was misidentified, and that Planorbis
campanulatus Say, 1821 and not Planorbis bicarinatus Say, 1819 was
meant. But since the incorrect type species Planorbis bicarinatus has
been regarded as type, it would be convenient to fix this as type
under Art. 70.3.
Type fixation in the original work:
Original designation (31 %)
Montfort 1810 established the genus
Theodoxus (Gastropoda) and
Theodoxus lutetianus Montfort 1810 as type species (now
Vest 1867 established the subgenus Clausilia (Isabellaria)
(Gastropoda) and designated Clausilia isabellina Pfeiffer, 1842 as
type species (now Isabellaria isabellina).
Riedel 1987 established the genus Turcozonites (Gastropoda) and
designated Zonites wandae Riedel, 1982 as type species (now
Monotypy (28 %)
Anodonta Lamarck, 1799 (Bivalvia) was originally established with one
included nominal species, Mytilus cygneus Linnæus, 1758. This is the
type species fixed by monotypy (now
Microcondylaea Vest 1866 (Bivalvia) was originally established with
two included nominal species, Unio bonellii Férussac, 1827 and with
Anodonta lata Rafinesque, 1820. Doubtfully included species do
not count, type species is Unio bonellii fixed by monotypy (now
Absolute tautonymy (2 %)
Kobelt 1871 established the gastropod genus-group name
included 23 species. Among these was Glischrus candidula Studer 1820.
Glischrus candidula is type species fixed by absolute tautonymy (now
Draparnaud 1801 established the gastropd genus
Succinea and included
Succinea amphibia Draparnaud 1801 and
Draparnaud 1801. Among the synonyms of S. amphibia, Draparnaud listed
a name Helix succinea Müller 1774. Synonyms do count here, so Helix
succinea is type species by absolute tautonymy (now
Kobelt 1904 established the gastropod subgenus Iberus (Balearica) and
included 10 species. Among these was Helix balearica Rossmässler
1838, which Kobelt cited as Iberus (Balearica) balearicus. The ending
-us is irrelevant here, Helix balearica is type species by absolute
tautonymy (currently Iberellus balearicus or Iberellus hispanicus).
Euxinolauria Lindholm, 1924 (Gastropoda: Lauriidae) was established as
a new replacement name for Caucasica Caziot & Margier, 1909 (not
Caucasica Boettger, 1877 (Gastropoda: Clausiliidae)). Caucasica Caziot
& Margier, 1909 contained originally four species, among which was
Pupa caucasica Pfeiffer, 1857. This is the type species for Caucasica
Caziot & Margier, 1909 fixed by absolute tautonymy, and also for
Euxinolauria (now Euxinolauria caucasica).
The following examples do not represent absolute tautonymy: Scomber
scombrus Linnæus, 1758 (Actinopterygii), Babyrousa babyrussa
(Linnæus, 1758) (Mammalia),
Suricata suricatta (Schreber, 1776)
Merlangius merlangus (Linnæus, 1758) (Actinopterygii),
Isabellaria isabellina (Pfeiffer, 1842) (Gastropoda), Rupestrella
rupestris (Philippi, 1836) (Gastropoda).
Linnean tautonymy (0.3 %)
Linnæus 1758 established Castor (Mammalia) and included two species,
Castor fiber and Castor moschatus. Among the synonyms of Castor fiber
was cited the one-word name Castor with references to six pre-Linnean
works (Gesner 1598, Rondelet 1554, Jonston 1650, Dodart 1676, Ray 1693
and Aldrovandi 1649).
Castor fiber Linnæus 1758 is type species fixed
by Linnean tautonymy (now Castor fiber).
Subsequent methods of type fixation:
Subsequent monotypy (2 %)
Valvata Müller, 1773 (Gastropoda) was established with a short
description and without species. Müller 1774 included one species
Valvata cristata Müller 1774.
Valvata cristata is type species by
subsequent monotypy (now
Omphiscola Rafinesque, 1819 (Gastropoda) was established without
species included. Beck 1837  included one species Buccinum
glabrum Müller, 1774. Buccinum glabrum is type species by subsequent
Subsequent absolute tautonymy (only very few cases)
Alosa Garsault, 1764 (Actinopterygii) was established without included
species. As first author, Cuvier, 1829 included two species Clupea
alosa and Clupea fincta.
Type species is Clupea alosa Linnæus 1758 by
subsequent absolute tautonymy (now Alosa alosa).
Rupicapra Garsault, 1764 (Mammalia) was established without included
species. As first author, Blainville, 1816 included three species
Capra rupicapra Linnæus, 1758, Capra pudu, and Capra americana. Type
species is Capra rupicapra by subsequent absolute tautonymy (now
Subsequent Linnean tautonymy (only theoretical, there might be no
Subsequent designation (32 %)
Aplexa Fleming, 1820 (Gastropoda) was established with two species,
Bulla hypnorum Linnæus, 1758 and Bulla rivalis Turton, 1807.
Herrmannsen 1846 fixed Bulla hypnorum as type by subsequent
Pseudanodonta Bourguignat 1877 (Bivalvia) was established with seven
Anodonta complanata Rossmässler 1835, and six others.
Westerlund 1902 validly designated
Anodonta complanata as type species
A species-group name can have a name-bearing type specimen, but this
is not a requirement. In many cases species-group names have no type
specimens, or they are lost. In those cases the application of the
species-group name is usually based on common acceptance. If there is
no common acceptance, there are provisions in the Code to fix a
name-bearing type specimen that is binding for users of that name.
Fixing such a name-bearing type should only be done if this is
taxonomically necessary (articles 74.7.3, 75.2, 75.3).
Aptenodytes patagonica Miller, 1778 is either based on a type
specimen, perhaps deposited in the Natural History Museum London or
somewhere else, or its type is lost. This is now irrelevant because
the usage of the name (as Aptenodytes patagonicus) for the king
penguin is unambiguously accepted.
The name-bearing type for
Homo sapiens Linnæus, 1758 is deposited in
Uppsala (the bones of Carl von Linné). This is a lectotype designated
by Stearn 1959, correctly but unnecessarily because the usage of the
name was unambiguous at that time, and still is.
Links to the separate articles
Principle of coordination
Principle of typification
The code divides names in the following manner:
Names above the family group
The names above the family group are regulated only as to the
requirements for publication; there is no restriction to the number of
ranks and the use of names is not restricted by priority.
The names in the family, genus, and species groups are fully regulated
by the provisions in the code. There is no limitation to the number of
ranks allowed in the family group. The genus group has only two ranks:
genus and subgenus. The species group has only two ranks: species and
In the species group gender agreement applies. The name of a species,
in two parts, a binomen, say, Loxodonta africana, and of a subspecies,
in three parts, a trinomen, say Canis lupus albus, is in the form of a
Latin phrase, and must be grammatically correct Latin. If the second
part, the specific name (or the third part, the subspecific name) is
adjectival in nature, its ending must agree in gender with the name of
the genus. If it is a noun, or an arbitrary combination of letters,
this does not apply.
For instance, the generic name Equus is masculine; in the name Equus
africanus the specific name africanus is an adjective, and its ending
follows the gender of the generic name.
Equus zebra the specific name zebra is a noun, it may not be
"corrected" to "Equus zebrus".
Equus quagga burchellii
Equus quagga burchellii the subspecific name burchellii is a noun
in the genitive case ("of Burchell").
If a species is moved, therefore, the spelling of an ending may need
to change. If Gryllus migratorius is moved to the genus Locusta, it
Locusta migratoria. Confusion over Latin grammar has led to
many incorrectly formed names appearing in print. An automated search
may fail to find all the variant spellings of a given name (e.g., the
spellings atra and ater may refer to the same species).
Many laymen[who?], and some scientists[who?], object to continued
adherence to this rule, especially those who work with butterflies and
moths. This is for historical reasons. In 1758, Linnæus placed all
butterflies in the genus Papilio, which, after a few decades,
contained thousands of species. From the beginning, the gender of
Papilio was unclear, undecided, and disputed. Some authors regarded it
as masculine, others as feminine. Linnæus knew this problem and
avoided any statement. All his 250 specific names in the genus Papilio
were either nouns, indeclinable adjectives, or adjectives ending in
-is (which can be masculine or feminine but not neuter). He did not
use a single adjective ending in -us, -a, -um. P. Brown, Cramer,
Fabricius, Fueßlin, Goeze, Poda and Schrank regarded
masculine, Ménétriés, Pontoppidan and most modern authors as
feminine. In ICZN Opinion 278 from 1954, it was regarded as masculine.
In many cases lepidopterists would not change the ending of a name as
used by the author who established a name. So we find for example
Papilio fuscus or
Papilio macilentus, but also
Papilio osmana and
Papilio paradoxa. Only in a few cases are both versions found in the
Web (an example is
Papilio multicaudatus and
This works also with other butterfly genera of which the gender is
undisputed. Graphium appears neuter, but only the inconsistent
Graphium angolanus and
Graphium mandarinus are used, while
Graphium sandawanum can only be found with a neuter specific name.
Likewise, pairs are more frequently found in genera of which the
gender is not obvious: Delias castaneus and Delias gigantea, Belenois
albumaculatus and Belenois rubrosignata, Mylothris arabicus and
Mylothris ruandana. Even in moths, such pairs occur: Xylophanes
obscurus and Xylophanes turbata,
Manduca boliviana and Manduca
Sphinx caligineus and Sphinx formosana, Macroglossum
albolineata and Macroglossum vicinum. It may also occur that a
lepidopteran subspecies can have a different gender from the name of
the species, as for example in
Papilio multicaudata pusillus Austin
& Emmel, 1998, and
Papilio torquatus flavida Oberthür, 1879.
Written nomenclatural rules in zoology were compiled in various
countries since the late 1830s, such as Merton's Rules and
Strickland's codes going back to 1843. At the first and second
International Zoological Congresses (Paris 1889, Moscow 1892)
zoologists saw the need to establish commonly accepted international
rules for all disciplines and countries to replace conventions and
unwritten rules that varied across disciplines, countries, and
Compiling "International Rules on Zoological Nomenclature" was first
proposed in 1895 in Leiden (3rd International Congress for Zoology)
and officially published in three languages in 1905 (French, English,
German; only French was official). From then on, amendments and
modifications were subsequently passed by various zoological
congresses (Boston 1907, Graz 1910, Monaco 1913, Budapest 1927, Padua
1930, Paris 1948, Copenhagen 1953, and London 1958). These were only
published in English, and can only be found in the reports of these
congresses or other official publications.
The 1905 rules became increasingly outdated. They soon sold out, and
it became increasingly difficult to obtain to a complete set of the
Rules with all amendments. In Copenhagen 1953 the French and
English texts of the rules were declared of equivalent official force,
and a declaration was approved to prepare a new compilation of the
rules. In 1958, an Editorial Committee in London elaborated a
completely new version of the nomenclatural rules, which were finally
published as the first edition of the ICZN Code on 9 November 1961.
The second edition of the code (only weakly modified) came in 1963.
The last zoological congress to deal with nomenclatural problems took
place in Monte Carlo 1972, since by then the official zoological
organs no longer derived power from zoological congresses. The
third edition of the code came out in 1985. The present edition is the
4th edition, effective since 2000. These code editions were elaborated
on by editorial committees appointed by the International
Commission on Zoological Nomenclature. The
ICZN Commission takes its
power from a general biological congress (IUBS, International Union of
Biological Sciences). The editorial committee for the fourth edition
was composed of seven persons. Such new editions of the ICZN Code are
not democratically approved by those taxonomists who are forced to
follow the code's provisions, neither do taxonomists have the right to
vote for the members of the commission or the editorial committee.
As the commission may alter the code (by declarations and amendments)
without issuing a new edition of the book, the current edition does
not necessarily contain the actual provision that applies in a
particular case. The Code consists of the original text of the fourth
edition and Declaration 44. The code is published in an English and a
French version; both versions are official and equivalent in
force, meaning, and authority. This means that if something in the
English code is unclear or its interpretation ambiguous, the French
version is decisive, and if there is something unclear in the French
code, the English version is decisive.
The rules in the code apply to all users of zoological names. However,
its provisions can be interpreted, waived, or modified in their
application to a particular case when strict adherence would cause
confusion. Such exceptions are not made by an individual scientist, no
matter how well-respected within the field, but only by the
International Commission on Zoological Nomenclature, acting on behalf
of all zoologists. The commission takes such action in response to
proposals submitted to it.
Carl Linnaeus named the domestic cat Felis catus in 1758; Johann
Christian Daniel von Schreber named the wildcat Felis silvestris in
1775. For taxonomists who consider these two kinds of cat a single
species the principle of priority means that the species ought to be
named F. catus, but in practice almost all biologists have used F.
silvestris. In 2003, the commission issued a ruling (Opinion 2027)
that "conserved the usage of 17 specific names based on wild species,
which are pre-dated, by or contemporary with those based on domestic
forms", confirming F. silvestris for the wild cat. Taxonomists who
consider the domesticated cat the same species as the wild cat should
use F. silvestris; taxonomists who consider the domesticated cat a
subspecies of the wild cat should use F. silvestris catus; taxonomists
who consider the domesticated cat a separate species should use F.
The latest amendments enacted by the commission concern electronic
publishing, which is now permitted for works published under an ISBN
ISSN after 2011 in a way that ensures registration with
well as archival of multiple copies.
Local usage and name changes
The ICZN is used by the scientific community worldwide. Changes are
governed by guidelines in the code. Local changes, such as the
changes proposed by the Turkish government, are not recognised by
The current (fourth edition) code is cited in scientific papers as
ICZN (1999) and in reference lists as:-
ICZN 1999. International Code of Zoological Nomenclature. Fourth
Edition. The International Trust for Zoological Nomenclature, London,
UK. 306 pp.
Strickland, H.E. [et al.] 1843. Report of a committee appointed "to
consider of the rules by which the Nomenclature of
Zoology may be
established on a Uniform and Permanent Basis." ["The Strickland
Code".] In: Report of 12th Meeting of the
British Association for the
Advancement of Science, June 1842, p. 105-121. BHL. [Also
published in the Philosophical Magazine and the Annals of Natural
Strickland, H.E. 1878. Rules for Zoological Nomenclature. John Murray,
London. Internet Archive.
Blanchard, R., Maehrenthal, F. von & Stiles, C. W. 1905. Règles
internationales de la nomenclature zoologique adoptées par les
Congrès Internationaux de Zoologie. International Rules of Zoological
Nomenclature. Internationale Regeln der Zoologischen Nomenklatur.
Rudeval, Paris. Google Books.
ICZN. 1961. International Code of Zoological Nomenclature: adopted by
the XV International Congress of Zoology. The International Trust for
Zoological Nomenclature, London, UK. BHL.
ICZN. 1964. International Code of Zoological Nomenclature. Second
edition. The International Trust for Zoological Nomenclature, London,
ICZN. 1985. International Code of Zoological Nomenclature. Third
edition. The International Trust for Zoological Nomenclature, London,
ICZN. 1999. International Code of Zoological Nomenclature. Fourth
edition. The International Trust for Zoological Nomenclature, London,
UK. BHL. The Code Online (ICZN).
Author citation (zoology)
List of authors of names published under the ICZN
International Code of Nomenclature for algae, fungi, and plants
^ ICZN Code Art. 5
^ ICZN Code Art. 86.3
^ ICZN Code Art. 89
^ a b c d ICZN Code Glossary
^ ICZN Code Glossary, "binomen"
^ ICZN Code Art. 24.2.
^ The publication by [Vallot] (1801) has not been unambiguously
recognized as published work in the sense of the Code Art. 8, which
might be another reason to ignore Art. 59.3 in this case.
^ Moscow State University hemihomonyms database
^ These proportions apply to 366 verified European non-marine mollusc
genera ([www.animalbase.org]), presumed to represent a more-or-less
representative animal group.
^ "Subsequent absolute tautonymy" is not used as a term in the Code's
fourth edition, but it is a logical consequence of the usage of the
term "subsequent monotypy".
^ AnimalBase: List of all taxa, sorted by genus names, Papilio
^ Allen, JA (1897). "The Merton Rules". Science. 6 (131): 9–19.
doi:10.1126/science.6.131.9. PMID 17819182.
^ Strickland, HE (1878). Rules for Zoological Nomenclature. John
^ Dayrat, B (2010). "Celebrating 250 Dynamic Years of Nomenclatural
Debates". In Polaszek, A. Systema Naturae 250 - The Linnaean Ark
(PDF). Taylor and Francis. Archived from the original (PDF) on
^ Blanchard, R., Maehrenthal, F. von & Stiles, C. W. 1905. Règles
internationales de la nomenclature zoologique adoptées par les
Congrès Internationaux de Zoologie. International Rules of Zoological
Nomenclature. Internationale Regeln der Zoologischen Nomenklatur. -
^ pp. V-VI in Kraus, O. 1962. Internationale Regeln für die
Zoologische Nomenklatur. Beschlossen vom XV. Internationalen Kongress
für Zoologie. - pp. I-VIII [= 1-8], 1-90. Frankfurt am Main.
(Senckenbergische Naturforschende Gesellschaft).
^ ICZN Code Art. 77.2
^ ICZN Constitution Art. 16.2
^ French Code online
^ ICZN Code Art. 86.2
Opinion 2027 (Case 3010): Usage of 17 specific names based on wild
species that are pre-dated by, or contemporary with, those based on
domestic animals (Lepidoptera, Osteichthyes, Mammalia)". Bulletin of
Zoological Nomenclature. International Commission on Zoological
Nomenclature. 60 (1). 31 March 2003. Archived from the original on 21
August 2007. Retrieved 8 October 2008.
International Commission on Zoological Nomenclature (2012).
"Amendment of Articles 8, 9, 10, 21 and 78 of the International Code
of Zoological Nomenclature to expand and refine methods of
publication". ZooKeys. 219: 1–10.
^ Scott L. Wing Causes and Consequences of Globally Warm Climates in
the Early ... - 2003 No 369 - Page 288 "Following the general practice
of naming species after localities by ending with "-ensis," Schnack
(2000) proposed to change the name Discorbis duwi to Discorbis
duwiensis. However, the International Code of Zoological Nomenclature
(Chapter 7 Article 32) does not allow such a change"
Text of the code
ZooBank: The World Register of
Proposed amendment of the International Code of Zoological
Nomenclature to expand and refine meth