An illustrated key to the described valid species of Trimma (Teleostei: Gobiidae) RICHARD WINTERBOTTOM Curator Emeritus, Department of Natural History, Royal Ontario Museum, 100 Queen’s Park, Toronto, Ontario, M5S 2C6, Canada Professor Emeritus, Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 1A1, Canada E-mail:
[email protected] Abstract 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 Comments on the variation of the mitochondrial genetic marker COI- 5P, derived from an unpublished neighbor-joining network based on 844 tissue samples, are also included where available. Key words: ichthyology, taxonomy, coral-reef fishes, pygymygobies, Indo-Pacific Ocean, mtDNA, barcoding. Citation: Winterbottom, R. (2019) An illustrated key to the described valid species of Trimma (Teleostei: Gobiidae). Journal of the Ocean Science Foundation, 34, 1–61. doi: https://doi.org/10.5281/zenodo.3525430 Introduction In 1906, Jordan & Seale erected a new genus, Trimma, for a new species they described from Samoa, T. caesiura. The diagnosis of their new taxon is not especially enlightening. They merely stated that it was similar to Eviota, but differed in having the region before the dorsal fin fully scaled, and that the “texture” of “the species is firmer and less translucent” (op.cit., p.