Why is the Genus *Gulo* considered monotypic within the Mustelidae family?

It contains only one living species, *Gulo gulo*.

The term monotypic, when applied to a biological genus like *Gulo*, signifies that the genus contains only a single extant species. In this specific case, the genus *Gulo* is composed solely of *Gulo gulo*, the wolverine. This taxonomic placement highlights a significant evolutionary divergence from its relatives within the broader Family Mustelidae, such as martens or badgers. While many related genera, like *Mustela*, harbor numerous species, the singularity of *Gulo* suggests that the wolverine's unique combination of traits—including its immense size relative to other mustelids and its extreme specialization for cold, harsh environments—has kept it evolutionarily distinct enough from its kin to warrant its own genus designation.