Incertae sedis
Incertae sedis"of uncertain position (seat)"is a term used to define a taxonomic group where its broader relationships are unknown or undefined.

# Examples
The taxonomy for humans is usually recognized as follows:
- Empire Neomura - along with all the living organisms.
Domain Eukaryota - along with all other nucleated organisms.
Kingdom Animalia - along with all other animals
Phylum Chordata - along with all other vertebrates and the invertebrate chordates
Class Mammalia - along with all other mammals
Order Primates - along with all other primates
Family Hominidae - along with all other apes
Subfamily Homininae - along with gorillas and chimps
Tribe Hominini - along with chimps
Subtribe Hominina - along with Australopithecus and prehistoric humans
Genus Homo - along with Homo erectus and other prehistoric humans
Species H. sapiens - humans
- Domain Eukaryota - along with all other nucleated organisms.
Kingdom Animalia - along with all other animals
Phylum Chordata - along with all other vertebrates and the invertebrate chordates
Class Mammalia - along with all other mammals
Order Primates - along with all other primates
Family Hominidae - along with all other apes
Subfamily Homininae - along with gorillas and chimps
Tribe Hominini - along with chimps
Subtribe Hominina - along with Australopithecus and prehistoric humans
Genus Homo - along with Homo erectus and other prehistoric humans
Species H. sapiens - humans
- Kingdom Animalia - along with all other animals
Phylum Chordata - along with all other vertebrates and the invertebrate chordates
Class Mammalia - along with all other mammals
Order Primates - along with all other primates
Family Hominidae - along with all other apes
Subfamily Homininae - along with gorillas and chimps
Tribe Hominini - along with chimps
Subtribe Hominina - along with Australopithecus and prehistoric humans
Genus Homo - along with Homo erectus and other prehistoric humans
Species H. sapiens - humans
- Phylum Chordata - along with all other vertebrates and the invertebrate chordates
Class Mammalia - along with all other mammals
Order Primates - along with all other primates
Family Hominidae - along with all other apes
Subfamily Homininae - along with gorillas and chimps
Tribe Hominini - along with chimps
Subtribe Hominina - along with Australopithecus and prehistoric humans
Genus Homo - along with Homo erectus and other prehistoric humans
Species H. sapiens - humans
- Class Mammalia - along with all other mammals
Order Primates - along with all other primates
Family Hominidae - along with all other apes
Subfamily Homininae - along with gorillas and chimps
Tribe Hominini - along with chimps
Subtribe Hominina - along with Australopithecus and prehistoric humans
Genus Homo - along with Homo erectus and other prehistoric humans
Species H. sapiens - humans
- Order Primates - along with all other primates
Family Hominidae - along with all other apes
Subfamily Homininae - along with gorillas and chimps
Tribe Hominini - along with chimps
Subtribe Hominina - along with Australopithecus and prehistoric humans
Genus Homo - along with Homo erectus and other prehistoric humans
Species H. sapiens - humans
- Family Hominidae - along with all other apes
Subfamily Homininae - along with gorillas and chimps
Tribe Hominini - along with chimps
Subtribe Hominina - along with Australopithecus and prehistoric humans
Genus Homo - along with Homo erectus and other prehistoric humans
Species H. sapiens - humans
- Subfamily Homininae - along with gorillas and chimps
Tribe Hominini - along with chimps
Subtribe Hominina - along with Australopithecus and prehistoric humans
Genus Homo - along with Homo erectus and other prehistoric humans
Species H. sapiens - humans
- Tribe Hominini - along with chimps
Subtribe Hominina - along with Australopithecus and prehistoric humans
Genus Homo - along with Homo erectus and other prehistoric humans
Species H. sapiens - humans
- Subtribe Hominina - along with Australopithecus and prehistoric humans
Genus Homo - along with Homo erectus and other prehistoric humans
Species H. sapiens - humans
- Genus Homo - along with Homo erectus and other prehistoric humans
Species H. sapiens - humans
- Species H. sapiens - humans
If modern humans were newly discovered or considered to be a taxonomic enigma, they might be given the rank of incertae sedis.  For example, if it were uncertain how Homo related to other members of the family Hominidae, a list of the great apes would look like this:
- Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Primates
Family Hominidae
Genus Homo incertae sedis
Subfamily Ponginae - orangutan
Subfamily Homininae - gorilla and chimpanzees
- Phylum Chordata
Class Mammalia
Order Primates
Family Hominidae
Genus Homo incertae sedis
Subfamily Ponginae - orangutan
Subfamily Homininae - gorilla and chimpanzees
- Class Mammalia
Order Primates
Family Hominidae
Genus Homo incertae sedis
Subfamily Ponginae - orangutan
Subfamily Homininae - gorilla and chimpanzees
- Order Primates
Family Hominidae
Genus Homo incertae sedis
Subfamily Ponginae - orangutan
Subfamily Homininae - gorilla and chimpanzees
- Family Hominidae
Genus Homo incertae sedis
Subfamily Ponginae - orangutan
Subfamily Homininae - gorilla and chimpanzees
- Genus Homo incertae sedis
- Subfamily Ponginae - orangutan
- Subfamily Homininae - gorilla and chimpanzees
Likewise, if humans were known to be primates, but no other relationships were clear, a taxonomy of the primates would look like this:
- Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Primates
Genus Homo incertae sedis
Family Cercopithecidae - Old World monkeys
Family Hominidae - apes
Family Lemuridae - lemurs
Etc.
- Phylum Chordata
Class Mammalia
Order Primates
Genus Homo incertae sedis
Family Cercopithecidae - Old World monkeys
Family Hominidae - apes
Family Lemuridae - lemurs
Etc.
- Class Mammalia
Order Primates
Genus Homo incertae sedis
Family Cercopithecidae - Old World monkeys
Family Hominidae - apes
Family Lemuridae - lemurs
Etc.
- Order Primates
Genus Homo incertae sedis
Family Cercopithecidae - Old World monkeys
Family Hominidae - apes
Family Lemuridae - lemurs
Etc.
- Genus Homo incertae sedis
- Family Cercopithecidae - Old World monkeys
- Family Hominidae - apes
- Family Lemuridae - lemurs
- Etc.

# Reasons a group might be considered incertae sedis

## Not included in an analysis
If a formal phylogenetic analysis is conducted that does not include a certain taxon, the authors might choose to label the taxon incertae sedis instead of guessing as to its placement.  This is particularly common when molecular phylogenies are generated since tissue for many rare organisms is hard to obtain.  It is also a common scenario when fossil taxa are included since many fossils are defined based on partial information.  For example, if the phylogeny was constructed using soft tissue and vertebrae 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.

## Basal taxa
There is a growing trend (see phylogenetic taxonomy) among taxonomists to place a basal taxon in the clade that contains its ancestors, but to refrain from giving it any more specific taxonomic ranks.  For example, the ancestor to all primates would be placed in the Order Primates, but would not be placed in a family at all.  Placing it in an individual family (such as Lemuridae) would suggest that it is more closely related to members of that family (lemurs) than to other primates when, in fact, it is equally related to all primates.
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