Are All Taxonomic Groups Uniquely Named? The Linnaean classification system classifies and groups organisms into taxonomic groups: Kingdom, Phylum, Class, etc. Obviously, a clade at any taxonomic level is uniquely determined by its classification at this level and all its parents in the hierarchy, e.g., Kingdom = _Bacteria_ , Phylum = _Firmicutes_ , Class = _Clostridia_ uniquely identifies a group of bacteria. But is this group also uniquely identified by just _Clostridia_? Or are there situations where two Phylums might both contain Classes with the same name? Since Genus & Species are typically used to identify organisms, I would assume that combinations of these at least are unique. As @Jam pointed out in the comments, Species alone is not enough. Note, however, that I am _not_ asking about the binomial name for a species - I am asking about uniqueness among higher levels of aggregation, such as Class, Order, and Family.

There are quite a few biological homonyms) (especially at the genus level, which apparently you aren't asking about). At the family taxonomic level, the Interim Register of Marine and Nonmarine Genera (IRMNG) currently lists 100 family names which are used for two or more distinct taxa.