The legion, in biological classification, is a non-obligatory taxonomic rank within the Linnaean hierarchy sometimes used in zoology.
In zoological taxonomy, the legion is:
Legions may be grouped into superlegions or subdivided into sublegions, and these again into infralegions.
Legions and their super/sub/infra groups have been employed in some classifications of birds and mammals. Full use is made of all of these (along with cohorts and supercohorts) in, for example, McKenna and Bell's classification of mammals. 
Dasyproctidae is a family of large South American rodents, comprising the agoutis and acouchis. Their fur is a reddish or dark colour above, with a paler underside. They are herbivorous, often feeding on ripe fruit that falls from trees. They live in burrows, and, like squirrels, will bury some of their food for later use.
Linnaean taxonomy can mean either of two related concepts:
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 and these groups are given a taxonomic rank; groups of a given rank can be aggregated to form a more inclusive group of higher rank, thus creating a taxonomic hierarchy. The principal ranks in modern use are domain, kingdom, phylum, class, order, family, genus, and species. The Swedish botanist Carl Linnaeus is regarded as the founder of the current system of taxonomy, as he developed a ranked system known as Linnaean taxonomy for categorizing organisms and binominal nomenclature for naming organisms.
In biological classification, the order is
Taeniolabidoidea is a group of extinct mammals known from North America and Asia. They were the largest members of the extinct order Multituberculata, as well as the largest non-therian mammals. Lambdopsalis even provides direct fossil evidence of mammalian fur in a fairly good state of preservation for a 60-million-year-old animal. Some of these animals were large for their time; Taeniolabis taoensis is the largest known multituberculate and though smaller, Yubaatar is the largest known Mesozoic Asian multituberculate. Average members of the Taeniolaboidea were about beaver-sized and the largest even reached sizes comparable to the largest beavers like Castoroides, up to about 100 kilograms.
Prototheria is a subclass to which the orders Monotremata, Morganucodonta, Docodonta, Triconodonta and Multituberculata have been assigned, although the validity of the subclass has been questioned.
Theria is a subclass of mammals amongst the Theriiformes. Theria includes the eutherians and the metatherians.
Paenungulata is a clade of "sub-ungulates", which groups three extant mammal orders: Proboscidea, Sirenia, and Hyracoidea (hyraxes). At least two more possible orders are known only as fossils, namely Embrithopoda and Desmostylia.
Systema Naturae is one of the major works of the Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the system, now known as binomial nomenclature, was partially developed by the Bauhin brothers, Gaspard and Johann, 200 years earlier, Linnaeus was first to use it consistently throughout his book. The first edition was published in 1735. The full title of the 10th edition (1758), which was the most important one, was Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis or translated: "System of nature through the three kingdoms of nature, according to classes, orders, genera and species, with characters, differences, synonyms, places".
Zatheria is a group (sublegion) of mammals that includes the common ancestor of Arguimuridae, Vincelestidae, Peramuridae, and Tribosphenida.
Simplicidentata is a group of mammals that includes the rodents and their closest extinct relatives. The term has historically been used as an alternative to Rodentia, contrasting the rodents with their close relatives the lagomorphs. However, Simplicidentata is now defined as including all members of Glires that share a more recent common ancestor with living rodents than with living lagomorphs. Thus, Simplicidentata is a total group that is more inclusive than Rodentia, a crown group that includes all living rodents, their last common ancestor, and all its descendants. Under this definition, the loss of the second pair of upper incisors is a synapomorphic feature of Simplicidentata. The loss of the second upper premolar (P2) has also been considered as synapomorphic for Simplicidentata, but the primitive simplicidentate Sinomylus does have a P2.
The bristle-spined rat is an arboreal rodent from Atlantic forest in eastern Brazil. Also known as the bristle-spined porcupine or thin-spined porcupine, it is the only member of the genus Chaetomys and the subfamily Chaetomyinae. It was officially described in 1818, but rarely sighted since, until December 1986, when two specimens - one a pregnant female - were found in the vicinity of Valencia in Bahia. Since then it has been recorded at several localities in eastern Brazil, from Sergipe to Espírito Santo, but it remains rare and threatened due to habitat loss, poaching and roadkills.
The Eocardiidae are an extinct family of caviomorph rodents from South America. The family is probably ancestral to the living family Caviidae, which includes cavies, maras, and capybaras and their relatives. McKenna and Bell (1997) divided eocardiids into two subfamilies, Luantinae for two of the oldest genera and Eocardiinae for remaining genera. Kramarz (2006) has recommended the abandonment of these subfamilies, as the genera placed in Luantinae appear to represent basal eocardiids, rather than a specialized side branch. The latter hypothesis had been proposed by Wood and Patterson (1959).
Phylogenetic nomenclature is a method of nomenclature for taxa in biology that uses phylogenetic definitions for taxon names as explained below. This contrasts with the traditional approach, in which taxon names are defined by a type, which can be a specimen or a taxon of lower rank, and a description in words. Phylogenetic nomenclature is currently regulated by the International Code of Phylogenetic Nomenclature (PhyloCode).
Suinae is a subfamily of artiodactyl mammals that includes several of the extant members of Suidae and their closest relatives – the domestic pig and related species, such as babirusas. Several extinct species within the Suidae are classified in subfamilies other than Suinae. However, the classification of the extinct members of the Suoidea – the larger group that includes the Suidae, the peccary family (Tayassuidae), and related extinct species – is controversial, and different classifications vary in the number of subfamilies within Suidae and their contents. Some classifications, such as the one proposed by paleontologist Jan van der Made in 2010, even exclude from Suinae some extant taxa of Suidae, placing these excluded taxa in other subfamilies.
The Hipposideridae are a family of bats commonly known as the Old World leaf-nosed bats. While it has often been seen as a subfamily, Hipposiderinae, of the family Rhinolophidae, it is now more generally classified as its own family. Nevertheless, it is most closely related to Rhinolophidae within the suborder Yinpterochiroptera.
In biological classification, taxonomic rank is the relative level of a group of organisms in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, order, class, phylum, kingdom, domain, etc.
Isotemnidae is an extinct family of notoungulate mammals known from the Paleocene to Middle Miocene of South America.
Cladotheria is a group (legion) of mammals that includes the ancestor of Dryolestida, Amphitheriida, Peramuridae and Zatheria.
Holotheria is an obsolete and diverse group of mammals that are descendants of the last common ancestor of Kuehneotherium and Theria.
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