An illustrated key to the described valid species of Trimma (Teleostei: Gobiidae)

An illustrated key to the 105 recognized valid species of the gobiid Trimma (pygmygobies), based on morphological and color-pattern characteristics is presented. Caution should be employed when using the key for specimens less than about 16 mm SL. A brief summary of what we know about the biology of the various species is given. Definitions and illustrations of the various characters used in the key are provided, along with the geographic range (where discernible) for each species. Details of the catalogue number and provenance of the holotype of each species (where known) are included. Comments on the variation of the mitochondrial genetic marker COI-5P, derived from an unpublished neighbor-joining network based on 844 tissue samples, are also included where available.