Incertae Sedis
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' () or ''problematica'' is a term used for a
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. ...
group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of
open nomenclature Open nomenclature is a vocabulary of partly informal terms and signs in which a taxonomist may express remarks about their own material. This is in contrast to synonymy lists, in which a taxonomist may express remarks on the work of others. Common ...
, uncertainty at specific taxonomic levels is indicated by ' (of uncertain family), ' (of uncertain suborder), ' (of uncertain order) and similar terms.


Examples

*The fossil plant '' Paradinandra suecica'' could not be assigned to any family, but was placed ''incertae sedis'' within the order
Ericales The Ericales are a large and diverse order of dicotyledons. Species in this order have considerable commercial importance including for Camellia sinensis, tea, persimmon, blueberry, kiwifruit, Brazil nuts, Argania, argan, and azalea. The order i ...
when described in 2001. * The fossil ''
Gluteus minimus The gluteus minimus, or glutæus minimus, the smallest of the three gluteal muscles, is situated immediately beneath the gluteus medius. Structure It is fan-shaped, arising from the outer surface of the ilium, between the anterior and infer ...
'', described in 1975, could not be assigned to any known animal
phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature f ...
. The genus is therefore ''incertae sedis'' within the kingdom
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. * While it was unclear to which order the
New World vulture The New World vulture or condor family, Cathartidae, contains seven extant species in five genera. It includes five extant vultures and two extant condors found in warm and temperate areas of the Americas. The "New World" vultures were widesprea ...
s (family Cathartidae) should be assigned, they were placed in Aves ''incertae sedis''. It was later agreed to place them in a separate order, Cathartiformes. * Bocage's longbill, ''Motacilla bocagii'', previously known as ''Amaurocichla bocagii'', is a species of
passerine bird A passerine () is any bird of the order Passeriformes (; from Latin 'sparrow' and '-shaped'), which includes more than half of all bird species. Sometimes known as perching birds, passerines are distinguished from other orders of birds by ...
that belongs to the superfamily
Passeroidea Passerida is, under the Sibley-Ahlquist taxonomy, one of two parvorders contained within the suborder Passeri (standard taxonomic practice would place them at the rank of infraorder). While more recent research suggests that its sister parvorde ...
. Since it was unclear to which family it belongs, it was classified as Passeroidea ''incertae sedis'', until a 2015 phylogenetic study placed it in '' Motacilla'' of
Motacillidae The wagtails, longclaws, and pipits are a family, Motacillidae, of small passerine birds with medium to long tails. Around 70 species occur in five genera. The longclaws are entirely restricted to the Afrotropics, and the wagtails are predominan ...
. *''
Parakaryon myojinensis ''Parakaryon myojinensis'', also known as the Myojin parakaryote, is a highly unusual species of single-celled organism known only from a single specimen, described in 2012. It has features of both prokaryotes and eukaryotes but is apparently d ...
'', a single-celled organism that is apparently distinct from
prokaryotes 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
eukaryotes Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...
.


In formal nomenclature

When formally naming a taxon, uncertainty about its taxonomic classification can be problematic. The
International Code of Nomenclature for algae, fungi, and plants The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all those "trad ...
, stipulates that "species and subdivisions of genera must be assigned to genera, and infraspecific taxa must be assigned to species, because their names are combinations", but ranks higher than the
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 ...
may be assigned ''incertae sedis''.


Reason for use


Poor description

This excerpt from a 2007
scientific paper : ''For a broader class of literature, see Academic publishing.'' Scientific literature comprises scholarly publications that report original empirical and theoretical work in the natural and social sciences. Within an academic field, scienti ...
about
crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...
s of the
Kuril–Kamchatka Trench The Kuril–Kamchatka Trench or Kuril Trench (russian: Курило-Камчатский жёлоб, ''Kurilo-Kamchatskii Zhyolob'') is an oceanic trench in the northwest Pacific Ocean. It lies off the southeast coast of Kamchatka and parallels ...
and the
Japan Trench The Japan Trench is an oceanic trench part of the Pacific Ring of Fire off northeast Japan. It extends from the Kuril Islands to the northern end of the Izu Islands, and is at its deepest. It links the Kuril–Kamchatka Trench to the north and ...
describes typical circumstances through which this category is applied in discussing:
...the removal of many genera from new and existing families into a state of incertae sedis. Their reduced status was attributed largely to poor or inadequate descriptions but it was accepted that some of the vagueness in the analysis was due to insufficient character states. It is also evident that a proportion of the characters used in the analysis, or their given states for particular taxa, were inappropriate or invalid. Additional complexity, and factors that have misled earlier authorities, are intrusion by extensive
homoplasies Homoplasy, in biology and phylogenetics, is the term used to describe a feature that has been gained or lost independently in separate lineages over the course of evolution. This is different from homology, which is the term used to characterize ...
, apparent character state reversals and
convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
.


Not included in an analysis

If a formal
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 is conducted that does not include a certain taxon, the authors might choose to label the taxon ''incertae sedis'' instead of guessing its placement. This is particularly common when
molecular phylogenies Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
are generated, since tissue for many rare organisms is hard to obtain. It is also a common scenario when
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 ...
taxa are included, since many fossils are defined based on partial information. For example, if the phylogeny was constructed using soft tissue and
vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
e as principal characters and the taxon in question is only known from a single tooth, it would be necessary to label it ''incertae sedis''.


Controversy

If conflicting results exist or if there is not a consensus among researchers as to how a taxon relates to other organisms, it may be listed as ''incertae sedis'' until the conflict is resolved.


Other ways of denoting uncertainty

Uncertain taxonomic assigations of other degrees may be denoted using the 'cf.' (before a taxon name) and '?' (after a taxon name) specifiers.


In zoological nomenclature

In zoological nomenclature, "''incertae sedis''" is not a nomenclatural term at all ''per se'', but is used by taxonomists in their classifications to mean "of uncertain taxonomic position".Glossary In botany, a name is not validly published if it is not accepted by the author in the same publication.Article 36.1 In zoology, a name proposed conditionally may be
available In reliability engineering, the term availability has the following meanings: * The degree to which a system, subsystem or equipment is in a specified operable and committable state at the start of a mission, when the mission is called for at a ...
under certain conditions.Articles 11 and 15 For uncertainties at lower levels, some authors have proposed a system of "open nomenclature", suggesting that question marks be used to denote a questionable assignment. For example, if a new species was given the
specific epithet 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 ...
''album'' by Anton and attributed with uncertainty to ''Agenus'', it could be denoted "''Agenus? album'' Anton (?Anton)"; the "(?Anton)" indicates the author that assigned the question mark. So if Anton described ''Agenus album'', and Bruno called the assignment into doubt, this could be denoted "''Agenus? album'' (Anton) (?Bruno)", with the parentheses around Anton because the original assignment (to ''Agenus'') was modified (to ''Agenus?'') by Bruno. This practice is not included in 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 is used only by paleontologists.


See also

*
Glossary of scientific naming This is a list of terms and symbols used in scientific names for organisms, and in describing the names. For proper parts of the names themselves, see List of Latin and Greek words commonly used in systematic names. Note that many of the abbreviat ...
* '' Nomen dubium'', a name of unknown or doubtful application * ''
Species inquirenda In biological classification, a ''species inquirenda'' is a species of doubtful identity requiring further investigation. The use of the term in English-language biological literature dates back to at least the early nineteenth century. The term t ...
'', a species that in the opinion of the taxonomist requires further investigation *
Wastebasket taxon Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used by some taxonomists to refer to a taxon that has the sole purpose of classifying organisms that do not fit anywhere else. They are typically defined ...
* ''Sui generis'' (biology) *
Unclassified language An unclassified language is a language whose genetic affiliation to other languages has not been established. Languages can be unclassified for a variety of reasons, mostly due to a lack of reliable data but sometimes due to the confounding inf ...


References


External links

* * {{Authority control Biological nomenclature Taxonomy (biology) Zoological nomenclature