tyrannulus

Tyrannulus is a taxonomic name derived from Latin tyrannus, tyrant, with the diminutive suffix -ulus, used historically in biology to denote a small or lesser form resembling a tyrant. In zoological nomenclature, Tyrannulus has appeared as a genus name in multiple groups, but it is not currently recognized as a valid, monophyletic lineage in contemporary classifications. Over time, various species that were once placed in Tyrannulus have been reassigned to other genera as taxonomic revisions clarified relationships among groups.

Because taxonomy is dynamic, the status of Tyrannulus can vary by source. Some references treat it as an obsolete or invalid name (a junior synonym, a nomen oblitum, or a misspelling) rather than a valid genus. In practice, Tyrannulus is not listed as an accepted taxon in major modern databases, and it does not denote a single, widely recognized group.

The term is morphologically reminiscent of Tyrannus, the genus that includes kingbirds and related birds in the tyrant flycatcher family Tyrannidae. When encountered in literature, Tyrannulus generally requires careful context to determine whether it refers to an historical usage, a synonym, or a misspelling.

See also Tyrannus, Tyrannidae, taxonomic nomenclature.